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Suvdagi vodorod aloqalarining ahamiyati nimada? va boshqa savollar:

Suvdagi vodorod aloqalarining ahamiyati nimada? va boshqa savollar:



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Bular juda oddiy savollar - asosiy biologiya - lekin men javob bergan usul hech bo'lmaganda to'g'ri ekanligiga ishonch hosil qilishni xohlayman.

  1. Vodorod aloqalari juda zaif, shuning uchun ular qanday qilib suv xususiyatlarida shunchalik muhim? Suvdagi vodorod aloqalari suvning o'ziga xos xususiyatlarini beradi: birlashish (suv molekulalarini bir -biriga bog'lab turish), yuqori o'ziga xos issiqlik (parchalanish paytida issiqlikni yutish, hosil bo'lganda issiqlikni chiqarish; harorat o'zgarishini minimallashtirish), yuqori bug'lanish issiqligi (bir nechta vodorod aloqalari singishi kerak. suvni bug'lantirish tartibi), muzning past zichligi (muzdagi molekulalar bir-biridan uzoqroq joylashgan) va eruvchanlik (qutbli molekulalar ionlar va qutbli birikmalarga tortilib, ularni suvda eriydi).
  2. Nega biz to'liq quriganimizdan ko'ra, suzishga borganimizdan so'ng darhol salqinroq his qilamiz? Biz suzishga borganimizdan so'ng, qurib qolganimizdan ko'ra darhol sovuqroq his qilamiz, chunki suvni bug'lantirish uchun juda ko'p issiqlik kerak; ammo, biz quriganimizdan keyin terimizdan ko'p suvni olib tashlaymiz va suv tezroq bug'lanadi.
  3. Agar suv qutbsiz bo'lsa, issiq kunda ko'chaga chiqsak, harorat tezroq qiziydimi yoki tezroq? Nima uchun? Tezroq. Chunki suv ichidagi vodorod aloqalari molekulalarning harakatini sekinlashtiradi va suvning o'ziga xos issiqlikka ega bo'lishiga imkon beradi.

  1. Siz vodorod aloqalari nima qilayotganini aytayapsiz, nima uchun ular juda zaif bo'lishiga qaramay, bunday yutuqlarga qodir emas. Ularning kuchi sonda. Xona haroratida suv molekulalarining to'liq beshdan biri boshqa suv molekulalari bilan to'rtta bog'lanish bilan shug'ullanadi, qolganlari esa ikkita shunday bog'lanish hosil qiladi. (Batafsil: http://www1.lsbu.ac.uk/water/hbond.html). Bundan farqli o'laroq, vodorod sulfidi kislorod va sulfid o'rtasida sezilarli o'xshashlikka qaramay, boshqa vodorod sulfid molekulalari bilan deyarli hech qanday vodorod aloqasini hosil qilmaydi. Kislorod va oltingugurt o'rtasidagi o'lchamdagi farq birinchisini ancha elektronegativ qiladi. Men boshqa vodorod birikmalari bilan davom etishim mumkin edi, lekin sizning birinchi savolingizga javob beradigan haqiqat: har bir suv molekulasi boshqa suv molekulalari bilan tengsiz miqyosda bir qator bog'lanishlarda ishtirok etadi.

Bundan tashqari, vodorod aloqalari boshqa molekulalar (dipol-dipol, van der Vals va boshqalar) ga qaraganda kuchliroq, masofa va burchakka qaraganda kuchliroqdir, shuning uchun ular kuchsiz bo'lib tuyulsa ham va alternativalar vodorod aloqalari kabi ko'p bo'lsa ham, ikkinchisi hali ham molekulalarni bog'lash qobiliyatiga ega bo'ladi.

  1. Suvni quritish ta'siri (bu suzishdan keyin, balki terlash, cho'milish yoki issiq oshibori bilan tozalashdan keyin ham keladi) suvning bug'lanishidan kelib chiqadi. Har bir holat, shu jumladan suyuq suvdan havodagi bug'larga o'tish, issiqlik iste'mol qiluvchi hodisadir. Teri quriganida, suvni bug'ga aylantirish uchun issiqlik bir joydan kelishi kerak. Terlash holatida bu insonning tanasidir.

E'tibor bering, suv bug'langanda sovutish nafaqat biz his qiladigan narsa, balki tug'ma tizimlarda ham sodir bo'ladigan jismoniy haqiqatdir. Masalan, Amazonka o'rmonlari va Sahroi Ekvatorga juda yaqin, lekin birinchisi ikkinchisiga qaraganda sovuqroq, chunki qisman issiqlik bug'lanish uchun ishlatiladi.

Sizning javobingiz yaxshi edi.

  1. Yana, siz haqsiz. Agar suv qutbli bo'lmaganida, u pastroq yashirin issiqlikka ega bo'lardi yoki oddiy aytganda, u ko'p issiqlik sarf qilmasdan bug'lanib ketardi. Agar ter qutbsiz bo'lmagan suyuqlikdan qilingan bo'lsa, u bug'langanda issiqlikni iste'mol qilmaydi, bu esa tezroq / tezroq isishi uchun qoladi.

Suv va vodorod aloqasi

Ko'pchilik kimyo talabalari molekula tuzilishini uning umumiy xossalari bilan bog'lashni tezda o'rganadilar. Shunday qilib, biz odatda kichik molekulalarning gaz yoki suyuqlik hosil qilishini kutamiz, va katta molekulalar oddiy sharoitda qattiq holda bo'lishini kutamiz.

Va keyin biz H ga kelamiz2Oh, va bashoratlarning ko'pi noto'g'ri ekanligini va suyuq suv (va hayotning o'zi) bizning sayyoramizda bo'lmasligi kerakligini bilganimdan hayron bo'ldim!

Ushbu darsda biz uchta yadro va o'n elektronning bu kichik birikmasi nima uchun uni biz biladigan 15 milliondan ortiq kimyoviy turlar orasida noyob qiladigan maxsus xususiyatlarga ega ekanligini bilib olamiz. [rasm]

Suvda har bir vodorod yadrosi markaziy kislorod atomiga kovalent tarzda bog'langan, ular bir -biriga bog'langan elektronlar bilan bog'langan. H.da2O, bu maqsadda kislorodning oltita tashqi qobiq elektronidan faqat ikkitasi ishlatiladi va ikkita bog'lanmaydigan juftlikka tashkil etilgan to'rtta elektron qoladi. Kislorodni o'rab turgan to'rtta elektron jufti manfiy zaryadli bulutlar orasidagi itarishni kamaytirish uchun bir -birlaridan iloji boricha uzoqroq joylashadilar. Bu odatda tetraedral geometriyaga olib keladi, unda elektron juftlari orasidagi burchak (va shuning uchun H-O-H) bog'lanish burchagi) 109,5°. Biroq, ikkita bog'lanmagan juft kislorod atomiga yaqinroq bo'lgani uchun, ular ikkita kovalent bog'lanish juftiga nisbatan kuchli turtki berib, ikki vodorod atomini bir-biriga yaqinroq itarib yuboradi. Natijada buzilgan tetraedral tartib hosil bo'ladi, bunda H —O —H burchagi 104,5 daraja.

Suvning katta dipol momenti vodorod bog'lanishiga olib keladi

H2O molekulasi elektr neytral, lekin musbat va manfiy zaryadlar bir tekis taqsimlanmagan. Bu sxematik diagrammada rangning gradatsiyasi bilan ko'rsatilgan. Elektron (salbiy) zaryad molekulaning kislorod uchida to'plangan, bu qisman bog'lanmagan elektronlar (qattiq ko'k doiralar) va kislorodning yuqori yadroviy zaryadi tufayli elektronlarga kuchliroq tortishish ta'sir qiladi. Bu zaryadning o'zgarishi $ a $ ni tashkil qiladi elektr dipol, pastki qismidagi o'q bilan ifodalangan ushbu dipolni suv molekulasining elektr "tasviri" deb o'ylashingiz mumkin.

Qarama -qarshi zaryadlar o'ziga jalb qiladi, shuning uchun bitta suv molekulasining manfiy uchi boshqa molekulaning musbat uchiga yaqinroq bo'lishga intilishi ajablanarli emas. Buning kuchi (bu erda batafsilroq tavsiflangan) oddiy kimyoviy bog'lanishdan kamroqdir va shuning uchun u gaz fazasida oddiy termal harakatlar bilan butunlay bostiriladi.

Suvda vodorod birikmasi

Ammo qachonki X2Suyuqlikda O molekulalari to'plangan, bu jozibali kuchlar juda sezilarli ta'sir ko'rsatadi, biz buni (biroz chalg'ituvchi) deymiz. vodorod bilan bog'lanish. Issiqlik harakatlarining buzuvchi ta'sirini o'chirish uchun etarlicha past haroratlarda suv muzga aylanadi, bunda vodorod aloqalari qattiq va barqaror tarmoq hosil qiladi.

Suvdagi vodorod aloqalari haqida hamma narsani bilish uchun LSBU sahifasiga qarang.

E'tibor bering, vodorod aloqasi (kesilgan yashil chiziq bilan ko'rsatilgan) kovalent O —H bog'lanishidan biroz uzunroq. Bu ham ancha zaifroq, 492 kJ mol &ndash1 ning O&ndashH kovalent bog'lanish kuchiga nisbatan taxminan 23 kJ mol &ndash1.

Suvni boshqa vodorod bilan bog'langan suyuqliklar orasida ham noyob qiladigan omillardan biri uning hosil qilishi mumkin bo'lgan ko'p miqdordagi vodorod aloqalariga nisbatan juda kichik massasidir. Issiqlik harakatlari natijasida bu zaif diqqatga sazovor joylar buzilganligi sababli, har qanday bitta vodorod aloqasining umri pikosekundda juda qisqa bo'ladi. Har qanday vaqtda o'rtacha H2O molekulasi to'rtdan kamroq qo'shni bilan bog'langan va mdash hisob-kitoblariga ko'ra 2,4 dan 3,6 gacha o'zgarib turadi.

Suv uzoq vaqtdan beri ma'lum bo'lgan boshqa kichik molekulalardan ajralib turadigan ko'plab fizik xususiyatlarga ega ekanligi ma'lum. Kimyogarlar buni suvning "kvantomik" xususiyatlari deb atashsa -da, ular hech qanday sirli emas, ular kislorod atomining o'lchami va yadro zaryadi boshqa elementlar atomlarining elektron zaryadli bulutlarini buzib ko'rsatishga qanday ta'sir qilishini oldindan aytib bo'lmaydi. kislorod bilan kimyoviy bog'langan.

Nima uchun suvning qaynash nuqtasi juda yuqori

Suvning eng ko'zga ko'ringan o'ziga xosligi uning juda yuqori qaynash nuqtasi Bunday yorug'lik molekulasi uchun. Suyuq metan CH4 (molekulyar og'irligi 16) &ndash161°C da qaynaydi,

Ushbu diagrammadan ko'rinib turibdiki, har xil 16 -guruh vodorod birikmalarining qaynash nuqtalarining H ga ekstrapolyatsiyasi2O, bu modda normal sharoitda gaz bo'lishi kerakligini ko'rsatadi.

Nima uchun suvning sirt tarangligi shunchalik yuqori

Boshqa suyuqliklar bilan solishtirganda, suv ham yuqori sirt tarangligi.

Hovuz yuzasi bo'ylab hasharotlar yurganini ko'rganmisiz? The suv haydovchi suv yuzasi elastik plyonka vazifasini bajaradi, uning ustiga ozgina og'irlik qo'yilganda deformatsiyaga qarshilik ko'rsatadi. (Agar ehtiyot bo'lsangiz, stakan ichidagi suv yuzasida kichik qog'oz qisqich yoki po'latdan yasalgan qistirmalarni ham "qoqib" qo'yishingiz mumkin.) Buning sababi sirt tarangligi suvdan. Suyuqlikning asosiy qismidagi molekula har tomonlama qo'shni molekulalarni o'ziga tortadi, lekin ular o'rtacha nolga teng bo'lgani uchun molekulada aniq kuch yo'q. O'zini topadigan molekula uchun da tashqi tomondan, vaziyat boshqacha, u faqat yon va pastga kuchlarni boshdan kechiradi.

Sirtda joylashgan va ichidagi chuqur molekulalar orasidagi farq, ayniqsa, Hda yaqqol namoyon bo'ladi2O, kuchli vodorod bog'lovchi kuchlari tufayli. Sirtdagi molekula va quyma suyuqlikda uchraydigan kuchlar orasidagi farq suyuqlikning sirt tarangligini keltirib chiqaradi.

Bu chizma ikkita H ni ajratib ko'rsatadi2O molekulalar, biri sirtda, ikkinchisi suyuqlikning asosiy qismida. Sirt molekulasi o'zining pastdagi va ikkala tomonidagi qo'shnilariga tortiladi, lekin sirt ustidagi 180 ° qattiq burchak burchagiga ishora qiluvchi hech qanday diqqatga sazovor joylar yo'q. Natijada, sirtdagi molekula suyuqlikning asosiy qismiga tortiladi. Ammo har doim sirt bo'lishi kerak bo'lganidan, umumiy ta'sir suyuqlikning sirtini kamaytirishdir.

Sirt maydonining hajmiga eng kichik nisbati bo'lgan geometrik shakl - bu shar, shuning uchun juda oz miqdordagi suyuqlik sferik tomchilar hosil qiladi. Tomchilar kattalashgan sari ularning vazni ularni odatdagi ko'z yosh shakliga aylantiradi.

Nima uchun muz suv ustida suzadi

H ning eng energetik jihatdan qulay konfiguratsiyasi2O molekulalari-har bir molekula to'rtta qo'shni molekula bilan vodorod bilan bog'langan molekula. Yuqorida tavsiflangan issiqlik harakati tufayli suyuqlikda bu idealga hech qachon erishilmaydi, lekin suv muzga aylanganda, molekulalar muz kristalida aynan shunday tartibga joylashadi. Bu tartib molekulalarning bir -biridan ancha uzoqroq bo'lishini taqozo etadi, aks holda, vodorod aloqasi maksimal bo'lgan muzning tuzilishi ochiq va suvga qaraganda pastroq bo'ladi.

Bu erda suvning (chapda) va muzning (o'ngda) tipik mahalliy tuzilishining uch o'lchovli ko'rinishlari keltirilgan. Muz strukturasining kattaroq ochiqligiga e'tibor bering, bu yagona, kengaytirilgan kristall panjarada vodorod bog'lanishining eng kuchli darajasini ta'minlash uchun zarurdir. Suyuq suvda ko'proq gavjum va chalkash tartib faqat muzlash nuqtasidan yuqori issiqlik energiyasi bilan ta'minlanishi mumkin. [rasm manbasi]

Muz eriganida, kuchliroq issiqlik harakati vodorod bilan bog'langan tuzilmaning ko'p qismini buzadi, bu molekulalarning yanada yaqinroq to'planishiga imkon beradi. Shunday qilib, suv qattiq shakli muzlash nuqtasidagi suyuqlikka qaraganda pastroq bo'lgan juda kam sonli moddalardan biridir. Mahalliylashtirilgan vodorod aloqalari klasterlari hali ham saqlanib qolmoqda, ammo ular doimiy ravishda uzilib, isloh qilinmoqda, chunki termal harakatlar individual molekulalarni silkitib, silkitib yuboradi. Suv harorati muzlash darajasidan yuqori bo'lganda, bu klasterlarning ko'lami va umri qisqaradi, shuning uchun suvning zichligi ortadi.

Yuqori haroratlarda hamma moddalar uchun umumiy bo'lgan boshqa ta'sir hukmronlik qila boshlaydi: harorat oshishi bilan issiqlik harakatlarining amplitudasi ham oshadi. Bu kuchliroq tebranish molekulalar orasidagi o'rtacha masofaning oshishiga olib keladi, bu esa suyuqlik zichligini kamaytiradi, bu oddiy termal kengayishdir.

Ikki raqobatdosh ta'sir (past haroratlarda vodorod bog'lanishi va yuqori haroratlarda termal kengayish) ikkalasi ham zichlikning pasayishiga olib kelganligi sababli, suvning zichligi maksimal darajadan o'tadigan harorat bo'lishi kerak. Bu harorat 4 ° C, bu siz muz bilan qoplangan ko'lning tubida topadigan suvning harorati bo'lib, unda barcha suvlarning eng zichligi sovuq suvni siqib chiqargan va uni sirtga yaqinroq surgan.

Suyuq suvning tabiati va H2Uning tarkibidagi O molekulalar tartibga solingan va o'zaro ta'sir ko'rsatadigan savollar ko'p yillar davomida kimyogarlarni qiziqtiradi. Ehtimol, ko'proq intensiv o'rganilgan suyuqlik yo'q va hozirda bu borada ulkan adabiyotlar mavjud.

Quyidagi faktlar yaxshi tasdiqlangan:

  • H2O molekulalari vodorod bog'lanishi deb nomlanuvchi maxsus turdagi dipol-dipolli o'zaro ta'sir orqali bir-birini o'ziga tortadi
  • vodorod bilan bog'langan klaster, unda to'rtta H2O'lar xayoliy tetraedrning burchaklarida joylashgan, ayniqsa qulay (past potentsial energiya) konfiguratsiya, lekin.
  • molekulalar pikosaniyali (10 㪤 soniya) vaqtli shkalada tez issiqlik harakatlarini o'tkazadi, shuning uchun har qanday maxsus klasterli konfiguratsiyaning ishlash muddati qisqa bo'ladi.

Suvning mikroskopik tuzilishini tekshirish uchun infraqizil yutilish, neytronlarning tarqalishi va yadroviy magnitli rezonans kabi turli xil usullar qo'llanilgan. Ushbu tajribalar va nazariy hisob-kitoblar natijasida olingan ma'lumotlar suvning tuzilishi va harakatini tushuntirishga harakat qiladigan yigirmaga yaqin "model" ni ishlab chiqishga olib keldi. So'nggi paytlarda, ushbu modellar suvning fizik xususiyatlarini qanday bashorat qila olishini aniqlash uchun har xil turdagi kompyuter simulyatsiyalari ishlatilgan.

Bu ish suyuq suvning tuzilishi haqidagi qarashlarimizni bosqichma -bosqich takomillashtirishga olib keldi, lekin hech qanday aniq javob bermadi. Buning bir qancha sabablari bor, lekin asosiysi shundaki, "tuzilma" (va suv "klasterlari") tushunchasining o'zi ham ko'rib chiqilayotgan vaqt doirasiga, ham hajmga bog'liq. Shunday qilib, quyidagi turdagi savollar hali ham ochiq.

  • Siz & quot; klaster & quot; a'zolarini o'sha klasterda bo'lmagan qo'shni molekulalardan qanday ajratasiz?
  • Alohida vodorod aloqalari doimiy ravishda pikosekundlik vaqt oralig'ida uzilib, qayta shakllanayotganligi sababli, suv klasterlari uzoq vaqt davomida biron bir mazmunli mavjudmi? Boshqacha qilib aytganda, klasterlar vaqtinchalik, holbuki & quot; tuzilish & quot; molekulyar tuzilishni nazarda tutadi. U holda suvning tuzilishini tavsiflashda "klasterlar" atamasidan qonuniy foydalana olamizmi?
  • Berilgan H atrofida qo'shni molekulalarning mumkin bo'lgan joylashuvi2O energetik va geometrik mulohazalar bilan cheklangan, shuning uchun har qanday kichik hajmli element ichida ma'lum miqdorda & quot; tuzilish & quot; paydo bo'ladi. Biroq, bu elementlar hajmi elementi kattalashgan sari, bu o'zaro bog'liqlik qanchalik aniq emas. Va yuqorida aytib o'tilganidek, bu tuzilmalar bir necha pikosaniyadan ko'proq vaqt davomida qanchalik saqlanadi?

1950-yillarda suyuq suv vodorod bilan bog'langan klasterlar aralashmasidan iborat deb taxmin qilingan (H.2O)n qaysi ichida n har xil qiymatlarga ega bo'lishi mumkin, lekin bunday agregatlarning mavjudligi to'g'risida kam dalillar topilgan. Kompyuter-modellashtirish va spektroskopiya yordamida qo'llab-quvvatlanadigan hozirgi ko'rinish shundan iboratki, suv juda qisqa vaqt ichida vodorod bilan bog'langan ulkan klasterdan tashkil topgan "quotel" ga o'xshaydi. Vaqt shkalasi bo'yicha 10 va ndash12-10 va ndash9 sekundlarda, aylanishlar va boshqa issiqlik harakatlari individual konfiguratsiyalarda alohida vodorod aloqalarini uzilishiga olib keladi, bu esa o'zgaruvchan mahalliy uzilishlarni keltirib chiqaradi, ularning darajasi va ta'siri harorat va bosimga bog'liq.

Suv tuzilishi haqidagi hozirgi qarashlar

1980-yillarda boshlangan molekulyar modellashtirish simulyatsiyalari katta ta'sir ko'rsatgan hozirgi fikrlash shuni ko'rsatadiki, juda qisqa vaqt oralig'ida (bir pikosekunddan kam) suv yagona, ulkan vodorod bilan bog'langan klasterdan tashkil topgan "gel" ga o'xshaydi. Vaqt shkalasi bo'yicha 10 -12 -10 -9 -sekundlarda, aylanishlar va boshqa issiqlik harakatlari, individual konfiguratsiyalarda alohida vodorod aloqalarini uzilishiga va qayta shakllanishiga olib keladi, bu esa o'zgaruvchan mahalliy uzilishlarni keltirib chiqaradi, ularning ta'siri va ta'siri harorat va bosimga bog'liq.

Richard SayKallining laboratoriyasida olib borilgan so'nggi tadqiqotlar shuni ko'rsatadiki, suyuq suvdagi vodorod aloqalari shunchalik tez parchalanib ketadiki (ko'pincha buzilgan konfiguratsiyalarda), bu suyuqlikni vodorod bilan bog'langan molekulalarning uzluksiz tarmog'i deb hisoblash mumkin.

Suyuq suvning kompyuter tomonidan yaratilgan nano o'lchovli ko'rinishi Boston universiteti Gen Stenli laboratoriyasidan olingan [manba]. Kislorod atomlari qizil, vodorod atomlari oq

Muz, barcha qattiq moddalar singari, har bir suv molekulasi to'rtta qo'shni H bilan o'ralgan yaxshi belgilangan tuzilishga ega.2Os. bulardan ikkitasi markaziy H dagi kislorod atomi bilan vodorod bogʻlangan2O molekulasi va ikkita vodorod atomining har biri boshqa qo'shni H bilan xuddi shunday bog'langan2O.

Muz olti burchakli panjarali tuzilishga ega bo'lgan kristallarni hosil qiladi, ular to'liq rivojlanishda ba'zan kvartsda bo'lgani kabi olti burchakli prizma hosil qiladi. Bu vaqti-vaqti bilan sodir bo'ladi va qishki alpinizm bilan shug'ullangan har bir kishi havoda suzayotgan muz kristallarining igna shaklidagi prizmalarini ko'rgan bo'lishi mumkin. Ammo, aksariyat sharoitlarda, biz ko'rgan qor parchalari kristallari, odatda, kuzatiladigan, fraktalga o'xshash olti burchakli chiroyli tuzilmalarga tekislanadi.

Qor parchalari

H2Prizmaning yuqori va pastki tekis yuzalarini tashkil etuvchi O molekulalar juda chambarchas o'ralgan va ichidagi molekulalar bilan (vodorod bog'i orqali) bog'langan. Bundan farqli o'laroq, prizmaning yon tomonlarini tashkil etuvchi molekulalar va ayniqsa, olti burchakli burchaklardagi molekulalar ancha ochiq bo'ladi, shuning uchun atmosfera H.2Kristal yuzasining aksariyat joylari bilan aloqa qiladigan O molekulalar juda erkin biriktiriladi va ular bu burchaklarga vodorod bog'langan birikmalar hosil qilish imkoniyatiga ega bo'lgunga qadar u bo'ylab ko'chib o'tadilar, shuning uchun qattiq qismga aylanadi va strukturani shu olti yo'nalish bo'ylab kengaytiradi. Bu jarayon o'zini davom ettiradi, chunki yangi kengaytmalar olti burchakli tuzilishga ega bo'ladi.

Nima uchun muz sirpanchiq?

200K dan past haroratlarda muz yuzasi juda tartibsiz va suvga o'xshaydi. Harorat muzlash nuqtasiga yaqinlashganda, buzilishning bu qismi sirtdan uzoqroqqa cho'zilib ketadi va moylovchi vazifasini bajaradi.

Rasm 2008 yil 7 apreldagi C & ampEN jurnalining sirtlarni o'rganishning zamonaviy usullarini kashf etgan fizik kimyogar Gabor Somorjayni sharaflash haqidagi maqoladan olingan.

Kimyogar uchun & quot; sof & quot atamasi faqat ma'lum bir dastur yoki jarayon kontekstida ma'noga ega. Biz laboratoriyada ishlatadigan distillangan yoki ionlashtirilmagan suvda erigan atmosfera gazlari va vaqti-vaqti bilan bir oz kremniy bor, lekin ularning oz miqdori va nisbiy harakatsizligi ko'p hollarda bu aralashmalarni ahamiyatsiz qiladi. Muayyan turdagi aniq o'lchovlar uchun olinadigan eng yuqori tozalikdagi suv talab qilinganda, u odatda filtrlanadi, deionizatsiyalanadi va uch marta vakuumli distillanadi. Hatto bu "kimyoviy jihatdan toza" suv ham izotopik turlarning aralashmasidir: vodorodning ikkita barqaror izotopi mavjud (H 1 va H 2, ikkinchisi ko'pincha D bilan belgilanadi) va kislorod (O 16 va O 18). H kabi2O 18, HDO 16 va boshqalar, bularning barchasi suv bug'ining infraqizil spektrlarida osongina aniqlanadi. Buning ustiga, suvdagi ikkita vodorod atomida magnit momentlari parallel yoki antiparlel bo'lishi mumkin bo'lgan protonlar mavjud bo'lib, ular vujudga keltiradi. orto- va para-navbati bilan suv. Ikkala shakl odatda a da mavjud u/s nisbati 3: 1.

ning miqdori suvdagi kislorod va vodorodning noyob izotoplari joydan joyga o'zgaradi, endi ma'lum bir suv namunasining yoshini va manbasini aniqlik bilan aniqlash mumkin. Bu farqlar organizmlarning H va O izotopik profillarida aks etadi. Shunday qilib, odamlarning sochlarini izotopik tahlil qilish jinoyatlarni tergov qilish va antropologik tadqiqotlar uchun foydali vosita bo'lishi mumkin. Shuningdek, Microbe Forensics sahifasiga va suv izotoplari haqidagi umumiy manbaga qarang.

Vodorod aloqalari, vodorod atomining elektron buluti, ko'proq elektrongativ atomlardan biriga bog'langanida, vodorodda qisman musbat zaryad qoldirganda hosil bo'ladi. Vodorod atomining juda kichik o'lchamlari tufayli, bu qisman zaryadning zichligi etarlicha katta bo'lib, u yaqin atrofdagi elektron-atom atomidagi yagona juft elektronlar bilan o'zaro ta'sir o'tkazishga imkon beradi. Garchi vodorod bog'lanishi odatda dipol-dipol tortishish shakli sifatida tasvirlansa-da, endi u ma'lum darajada elektron almashinuvini (tashqi bog'lanmagan elektronlar va vodorod o'rtasida) o'z ichiga olishi aniq, shuning uchun bu bog'lanishlar ba'zi kovalentlarga ega. belgi

Vodorod aloqalari oddiy kovalent aloqalarga qaraganda uzunroq va ular kuchsizroqdir. Vodorod bilan bog'lanishning eksperimental dalillari, odatda, vodorod va boshqa atomlar orasidagi odatdagidan ko'ra qisqa masofalarni ko'rsatadigan qattiq jismlarning rentgen nurlanish diffraktsiyasi tadqiqotlaridan kelib chiqadi.

Kichik molekulalarda vodorod bog'lanishi

Quyidagi misollar molekulalarda vodorod bog'lanishining keng doirasini ko'rsatadi.

Vodorod ftoridi (mp & ndash92, bp 33 & degC)-kondensatsiyalangan fazalarida kuchli vodorod bilan bog'langan yana bir keng tarqalgan modda.

Biopolimerlarda vodorod birikmasi

Vodorod bog'lanishi biologik kelib chiqishi tabiiy polimerlarida ikki jihatdan muhim rol o'ynaydi:

  • Qo'shni polimer zanjirlari orasidagi vodorod bog'lanishi (molekulyar aloqa)
  • Xuddi shu zanjirning turli qismlari orasidagi vodorod aloqasi (molekulalararo bog'lanish
  • Polimer zanjiridagi &ndashOH guruhlari bilan suv molekulalarining vodorod bog'lanishi ("bog'langan suv"), bu polimer shaklini saqlashga yordam beradi.

Keyingi misollar biopolimerlarning bir nechta turlarini ifodalaydi.

Tsellyuloza

Tsellyuloza glyukozaning chiziqli polimeridir (yuqoriga qarang), manbaga qarab 300 dan 10 000 dan ortiq birlikni o'z ichiga oladi. O'simliklarning asosiy tarkibiy qismi sifatida (daraxtlardagi lignin bilan birga) tsellyuloza er yuzida eng ko'p tarqalgan organik moddadir. Vodorod bog'lanishining roli bu erda ko'rsatilganidek, har bir molekulani o'zaro bog'lashdir. Bu choyshablar van der Vals kuchlari tomonidan bir -biriga bog'lab qo'yilgan qatorda to'planadi. Qo'shni stacklarning keyingi vodorod bog'lanishi ularni kuchliroq va qattiqroq tuzilishga birlashtiradi.

[Wikimedia Commonsdan olingan rasm]

Proteinlar

Bu polimerlar aminokislotalardan R & mdashCH (NH2) COOH biologik katalizatorlar (fermentlar) vazifasini bajarishi uchun zarur bo'lgan shaklini (ikkilamchi va uchlamchi tuzilishini) saqlab qolish uchun molekulalararo vodorod bog'lanishiga bog'liq. Protein tarkibiga kiritilgan vodorod bilan bog'langan suv molekulalari ham ularning strukturaviy yaxlitligi uchun muhimdir.

Oqsillardagi asosiy vodorod bog'lanishi "amino" qismlarining -N&mdashH guruhlari bilan "atsid" qismlarining -C=O guruhlari o'rtasida bo'ladi. Ushbu o'zaro ta'sirlar ikkilamchi strukturaning ikkita asosiy turini keltirib chiqaradi, bu aminokislotalar polimer zanjirining joylashishini anglatadi:

Alfa spirali

Beta-varaq

Garchi uglerod odatda elektronegativ deb hisoblanmasa ham, C & mdashH ---- X vodorod aloqalari ham oqsillarda muhim ahamiyatga ega ekanligi ma'lum.

DNK (deoksiribonuklein kislotasi)

Sizning kimligingiz butunlay vodorod aloqalariga bog'liq! DNK, ehtimol siz bilganingizdek, barcha tirik organizmlarning tuzilishi va funktsiyasini aniqlashdagi markaziy roli tufayli biopolimerlarning eng mashhuridir.

DNKning har bir zanjiri to'rt xil qatordan qurilgan nuklotid monomerlari a dan iborat deoksiriboza shakar, fosfat guruhlariva a azotli asos shartli ravishda A, T, C va G. harflari bilan aniqlangan DNKning o'zi ikkitadan iborat polinukletid zanjirlari Ular yuqorida tasvirlangan oqsil alfa spiraliga o'xshash konfiguratsiyada umumiy o'q atrofida o'ralgan. Shakar-fosfat orqa miya tashqi tomonda joylashganki, nukleotid asoslari ichki tomonda va bir-biriga qarama-qarshi joylashgan. Ikki ip bir zanjirdagi nukleotidning azot atomini boshqa zanjirda uning qarshisida joylashgan nukleotiddagi azot yoki kislorod bilan bog'laydigan vodorod bog'lari bilan birga tutiladi.

Bu konfiguratsiyadagi samarali vodorod aloqasi faqat A-T va C-G juftlari o'rtasida sodir bo'lishi mumkin, shuning uchun bu ikkita qo'shimcha juftlik yangi protein molekulalari qurilganda transkripsiya qilinadigan genetik ma'lumotni kodlaydigan & quotalphabetni tashkil qiladi.

DNK spiralining tashqi qismlariga vodorod bilan bog'langan suv molekulalari uning tuzilishini barqarorlashtirishga yordam beradi:

DNK va uning replikatsiyasi haqida ko'proq ma'lumot olish uchun ushbu ajoyib Vikipediya sahifasiga qarang.

[Radboud U, Gollandiyadan rasmlar]

Yuqorida keltirilgan asosiy fikrlarni yaxshi tushunganingizga ishonch hosil qiling.

  • Aniqlash uchta maxsus xususiyat o'zining kattaligidagi molekula uchun g'ayrioddiy bo'lgan suvni aniqlang va ularning vodorod bog'lanishidan qanday kelib chiqishini tushuntiring.
  • Bu nimani anglatishini tushuntiring vodorod bog'lanishi va uni keltirib chiqaradigan molekulyar tuzilish xususiyatlari.
  • Ning & quot; tuzilmasini & quot; ta'riflang, masalan suyuq suv.
  • Chizma strukturaviy misollar H dan boshqa uchta kichik molekulada vodorod bog'lanishi2O.
  • Vodorod bog'lanishning rolini aytib bering oqsillar va ichida DNK.

&nusxalash 2004-2017 Stiven Lower - oxirgi oʻzgartirilgan 2017-10-23

Ushbu veb-sayt haqida ma'lumot olish yoki muallif bilan bog'lanish uchun,
iltimos, qarang Chem1 virtual darslik bosh sahifa.

Chem1 virtual darsligining bosh sahifasi http://www.chem1.com/acad/virtualtextbook.html

Chem1 Moddaning holati: Suv qoplaydi suv va vodorod aloqasi Umumiy kimyo kursi uchun. ning bir qismidir Umumiy kimyo virtual darslik , Stiven Lower tomonidan umumiy kimyo bo'yicha bepul, onlayn ma'lumotnoma

Bu bob quyidagi mavzularni o'z ichiga oladi: H tabiati2O molekula, suvning & quotanomal & quot; xossalari, suyuq suvning tuzi, muz, & quot; toza suv va ichimlik suvi, kichik molekulalarda va biopolimerlarda vodorod bog'lanishi. Bunga to'g'ridan -to'g'ri http://www.chem1.com/acad/webtext/states/water.html orqali kirish mumkin.

Ushbu material asosan kollejning birinchi bosqichiga yo'naltirilgan, ammo uning ko'p qismi o'rta maktab o'quvchilari uchun ham mos keladi. U Creative Commons Attribution 3.0 Unported litsenziyasi ostida litsenziyalangan.


Vodorod aloqasi nima uchun muhim?

Vodorod aloqasi muhim, chunki u shunday hal qiluvchi ahamiyatga ega er yuzidagi barcha hayot uchun.

Bu erda vodorod bog'lanishi muhim bo'lgan uchta sabab.

1. DNKning tuzilishi

DNK juft spirali tuzilishga ega, chunki vodorod aloqalari asos juftlarini o'rtada ushlab turadi. Vodorod aloqalari bo'lmasa, DNK boshqa tuzilish sifatida mavjud bo'lishi kerak edi.

2. Suvning o'ziga xos issiqlik sig'imi/ qaynash nuqtasi

Vodorod aloqalari tufayli suv nisbatan yuqori qaynash nuqtasiga ega. Vodorod aloqalari bo'lmasa, suv taxminan -80 ° C da qaynaydi. Okeanlar va ko'llardagi suv tezda qaynab ketadi. Bu Yerdagi hayot uchun katta muammolarga olib keladi.

3. Oqsillarning tuzilishi

Vodorod aloqalari oqsillarning ikkilamchi tuzilmalarini - spiral va katlamli varaqni hosil qilishda muhim ahamiyatga ega.

Gemoglobin molekulasi to'rtta bo'linmadan iborat. Subbirliklardagi oqsillar vodorod aloqalari bilan bir-biriga bog'langan spirallarga o'ralgan. Shaklni saqlab qolish uchun vodorod aloqalarisiz gemoglobin ishlay olmaydi.


Vodorodli bog'lanish PPT (Suv va muzda vodorod birikmasi)

Vodorod bog'lari, Vodorod bog'lanish ta'rifi, Vodorod bog'lanishi, Suv va muzdagi vodorod bog'lanishi, Eng kuchli vodorod bog'lari, Vodorod aloqalariga misollar, Molekulyar vodorod bog'lanishi, Molekulyar vodorod bog'lanishi, Vodorod bog'larining turlari, Vodorod bog'larining xususiyatlari, Muhim bio- Vodorod aloqalarini hosil qila oladigan molekulalar, vodorod bog'lanishining kuchi, qutbli molekulalar suvda qanday eriydi, suvning erishi va bug'lanishining termodinamikasi va vodorod bog'lanishining ahamiyati, vodorod aloqasi suvning fizik, kimyoviy va g'ayrioddiy xususiyatlariga qanday ta'sir qiladi, vodorod soni. Har bir suv molekulasi uchun obligatsiyalar.

PPT oldindan ko'rishni yuklash uchun bir necha soniya sabr qiling.

Siz .. qila olasiz; siz ... mumkin YUKLASH ‘ -ni bosish orqali PPT Nusxasini yuklab oling ‘ havolasi menyu belgisi yuqoridagi PPT oldindan ko'rish (pastki o'ng burchak)


Yopishish

AP® Biologiya halokati kursini ko'rib chiqishda muhokama qiladigan birinchi ikkita xususiyat bir -biri bilan bog'liq: yopishish va birlashish. Yopishish suvning boshqa sirtga yopishib ketadigan molekulalarini bildiradigan xususiyatdir. Uyg'unlik suvning bir -biriga yopishgan suv molekulalarini bildiradigan xususiyati. Bu ikkala xususiyat ham vodorod bog'lanishiga va vodorod bog'lanishining suv molekulalarini qanday yo'naltirishiga bog'liq.

Adezyon muhim xususiyatdir. Yopishqoqlikni ko'rsatish uchun probirkani suv bilan to'ldiring. Siz suvning U yaratganini ko'rasiz. Bu U deyiladi meniskus. Meniskus suv probirkaning oynasiga yopishgani uchun hosil bo'ladi. Agar sizda yanada nozikroq probirkaga ega bo'lsangiz, meniskus chuqurlashishini ko'rasiz (suv yuqoriroq emaklaydi). Agar sizda sinov naychasi bo'lmasa, rasmga e'tibor bering.

Yopishish tabiiy ravishda sodir bo'ladi va daraxtlar baland bo'lishi mumkin. Daraxtlar suvni ildizlaridan oladi. Ildizlar suvga muhtoj bo'lgan barglardan uzoqda joylashgan. Ksilem - bu daraxtning tortishish kuchiga qarshi barglarga etib boradigan qismi. Ksilemma mayda kapillyarlardan tashkil topgan. Suv ksilemaga kirganda, suv kapillyarning yon tomonlariga yopishadi va barglarga o'tishiga imkon beradi. Bu jarayon kapillyar harakat deb ataladi va o'simliklarning omon qolishi uchun juda muhimdir.


Suv va vodorod bog'lanishining tuzilishiga umumiy nuqtai nazar

Ushbu birinchi AP Biologiya darsidagi asosiy g'oya shundan iboratki, hayot atomlardan butun sayyoragacha bo'lgan ierarxiya sifatida mavjud bo'lib, turli darajalar bir-biri bilan o'zaro aloqada bo'lib, biz atrofimizda ko'radigan murakkab biologiya olamini yaratadi.

Eng kichik darajadan boshlab & # 8211 atomlar – biz hayot uchun zamin yaratadigan qoidalar va o'zaro ta'sirlarni ko'rishni boshlashimiz mumkin. Haqiqatan ham, biz hayvonlarning xatti-harakatlaridan tortib o'simliklarning quyosh tomon burish yo'ligacha bo'lgan kuzatilishi mumkin bo'lgan biologiyaning aksariyati alohida hujayralardagi molekulyar o'zaro ta'sirlarning mahsulidir. Umuman olganda, har bir atom atomdagi protonlar, elektronlar va neytronlar sonidan kelib chiqadigan bir qator xususiyatlarni o'z ichiga oladi. Birlashtirilganda molekulalar, bu xususiyatlar umumiy molekulaning xususiyatlarini yaratish uchun o'zaro ta'sir qilishi mumkin.

Biz hali ham butun organizmlarni yaratishga yordam beradigan biologik molekulalar orasidagi murakkab o'zaro ta'sirlarni o'rganayotgan bo'lsak -da, hayot uchun o'ta muhim bo'lgan bitta molekula bor. Biz bu moddani suv deb ataymiz.

Suv deyarli har bir organizmning umumiy vaznining taxminan 60-90% ni tashkil qiladi. Suv nafaqat ko'pchilik hujayralarning ulkan foizini tashkil qiladi, balki suv bir qator molekulalarni eritish va tarqatish uchun mukammal hal qiluvchi beradi.

Water has this ability because it is a qutbli molekula. Polar molecules do not share their electrons equally. Water is made of three atoms – one oxygen and two hydrogens – represented by the chemical formula H2O. The oxygen atom is far more electronegative than the hydrogen atoms. The electrons within a water atom spend much more time circling the oxygen atom than the hydrogen atoms.

This hydrogen bonding can be clearly seen in the structure of pure ice. The water molecules within pure ice form hydrogen bonds with each other, creating a perfect lattice structure, as seen in the image below. In fact, the hydrogen bonds between molecules hold each molecule further apart than would normally happen. This makes ice less dense than liquid water, which is why your ice cubes float in a glass of water.

This results in a molecule that has a more negative side and a more positive side. The more negatively charged oxygen molecule tends to attract positive charges, while the hydrogen atoms tend to attract negative charges. This is what makes water such a great polar solvent.

When other polar substances are dissolved in water, the water molecules actively pull them apart – evenly distributing the introduced molecules throughout the solution. Bu deyiladi tarqalish, and it gives cells and organisms the ability to easily distribute certain polar substances throughout their cells and body.

On the other hand, because water is a polar solvent, it does not mix well with non-polar moddalar. Cells use this fact to their advantage. The lipid bilayer that surrounds all cells is composed of molecules with a polar head and a non-polar tail. The polar heads are attracted to the water, while the non-polar tails group together to exclude as much water as possible. The polar regions are “hydrophilic” because they are attracted to water, while the non-polar regions are “hydrophobic” because they tend to repel water.

Furthermore, water molecules interact through hydrogen bonding to create 3 very unique properties: cohesion, adhesion, va sirt tarangligi.

Cohesion is the ability of water to “stick” to itself. The hydrogen bonding between water molecules means they are more likely to stick together than break apart. You can see this property in action in a droplet of water. Instead of breaking apart and spreading across a surface, water droplets tend to stay intact.

Adhesion, on the other hand, is water’s ability to stick to various hydrophilic surfaces. This gives water the ability to move through certain porous materials by adhering to their surface. For example, if you place a droplet of water on a paper towel it will quickly spread out and move through the towel by adhering to individual fibers and “pulling” itself through the material.

Surface tension is not unique to water, but water does have a high surface tension compared to other liquids. Surface tension is a measure of how easily an object can penetrate a liquid. In water, this tension is increased by all the hydrogen bonding between water molecules. In effect, this makes water less volatile (less likely to evaporate), which allows large bodies of water to collect and remain a viable environment for life.

These three properties are important for many biological processes. For example, massive trees use the properties of adhesion, cohesion, and surface tension to help move water molecules from the roots to the leaves by creating a series of passageways that allow water to travel upward. Adhesion ensures that water keeps moving upward, while cohesion and surface tension help pull even more water to the leaves.

In all, this makes water one of the most important molecules for life as we know if. If water did not have these polar properties, cells would not be able to distribute nutrients or other substances, cell membranes would not function, and the entire biosphere and water cycle would not exist to support all kinds of life on Earth.


MCQ on Waterm pH and Buffers – Part 1 Biochemistry MCQ – 11

(1). Water is liquid at room temperature, the most important reason for this is the:
a. High boiling point of water
b. High melting point of water
v. High heat of vaporization of water
d. Cohesive forces due to hydrogen bonds in water

(2). Water is a ___
a. Polar solvent
b. Non polar solvent
v. An amphipathic solvent
d. Non polar uncharged solvent

(3). Polar molecules can readily dissolve in water. This is because:
a. Polar molecules can form hydrogen bonds with water
b. Polar molecules can replace water-water interaction with more energetically favourable water-solute interactions
v. Polar charged water can interact with the charge of polar molecules
d. All polar molecules are amphipathic in nature

(4). Most important reason for the unusual properties of water is:
a. The covalent bonding pattern in water molecule
b. The bond angle between the two hydrogen atoms in water
v. Hydrogen bonding between water molecules
d. Water can be immediately ionized at room temperature

(5). The H – O – H bond angle in water molecule is:
a. 104.0 o
b. 104.5 o
v. 105.0 o
d. 105.5 o

(6). Which of the following statement is true regarding the electronegativity of atoms in water molecule?
a. Hydrogen is more electronegative than oxygen
b. Hydrogen is less electronegative than oxygen
v. Electronegativity of hydrogen and oxygen is same
d. Oxygen and hydrogen do not have significant electronegativity in water

(7). Which of the following represent the current melting point, boiling point and heat of vaporization of water?
a. 0 o C 100 o C 2260 J/g
b. 100 o C 0 o C 2260 J/g
v. 0 o C 100 o C 1260 J/g
d. 100 o C 0 o C 1260 J/g

(8). The oxygen atom in the water molecule due to its high electronegativity bears _______
a. 1 δ + charge
b. 2 δ + charges
v. 1 δ – charge
d. 2 δ – charges

(9). Hydrogen bond is best represented as the electrostatic attraction between:
a. A hydrogen covalently bounded to an electronegative atom and another hydrogen atom
b. A hydrogen covalently bounded to an electronegative atom and another electronegative atom
v. Two electronegative atoms and a hydrogen atom
d. Two hydrogen atoms

(10). The bond dissociation energy of hydrogen bonds in water molecule is
a. 10 kJ / mol
b. 23 kJ/mol
v. 470 kJ/mol
d. 348 kJ/mol

11. Which of the following statement is correct regarding the hydrogen bonds in water?
a. Hydrogen bond is 10 % covalent and 90 % electrostatic
b. Hydrogen bond is 25% covalent and 75 % electrostatic
v. Hydrogen bond is 50% covalent and 50% electrostatic
d. Hydrogen bond is 100 % electrostatic

12. A single water molecule can form how many hydrogen bonds at a time? (theoretically possible value)

13. The life span of a hydrogen bond between two water molecule in liquid water is:

a. 1 – 20 seconds
b. 1 – 20 microseconds
v. 1 – 20 nano-seconds
d. 1 – 20 pico-seconds

14. The bond dissociation energy of O – H bond in water is:

a. 470 kJ/mol
b. 348 kJ/mol
v. 23 kJ/mol
d. 10 kJ/mol

15. What is the bond length of hydrogen bond between two water molecules in liquid water?

a. 0.0177 nm
b. 0.177 nm
v. 1.177 nm
d. 17.70 nm

Biology / Life Sciences MCQ: Biochemistry MCQ-11: (Multiple Choice Questions / Model Questions / Sample Questions in Biochemistry: Water and pH Part 1 with detailed answer key, explanations and references for preparing CSIR JRF NET Life Science Examination and also for other competitive examinations in Life Science / Biological Science such as ICMR JRF Entrance Exam, DBT BET JRF Exam, GATE (XL) Life Science Exam, GATE (BT) Biotechnology Exam, ICAR JRF Exam, University PG Entrance Exam, JAM Exam, GS Biology Exam, GRE, Medical Entrance Examination etc. This set of practice questions will help to build your confidence in Biochemistry to face the real examination. A large quantum of questions in our practice MCQ is taken from previous year question papers of various national and international Biology / Life Sciences competitive examinations. Please take advantage of our Lecture Notes, PPTs, Previous Year Questions, Mock Tests, and Video Tutorials for your preparation. You can download all these questions papers and study materials as PDF from our Slideshare account absolutely free

Detailed Answer Key, Explanations and References

1. Ans. (d). Cohesive forces due to hydrogen bonds in water

The physical state of water is determined by the compactness of packing of molecules. The stability of molecular packing depends up on the stability of interactions involved in molecular packing. These interactions will be maximum in solid state (ice in the case of water) and it will be decreased in liquid state (liquid water) and it will be further less in gaseous phase (water vapour). Cohesion is a type of interaction in which the molecules of same types are involved. (Opposite term adhesion: interaction of different types of molecules). The liquid nature of water at room temperature is due to the cohesive forces in the water which is provided by the large number of inter molecular hydrogen bonds between water molecules.

2. Ans. (a). Polar solvent

Water is a polar solvent. Water molecule consists of two hydrogen atoms bonded to an oxygen atom. The two hydrogen atoms in water are not arranged linearly, because the oxygen atom’s four sp3 hybrid orbitals extend roughly toward the corners of a tetrahedron. Hydrogen atoms occupy two corners of the tetrahedron, and the nonbonding electron pairs of the oxygen atom occupy the other two corners. Thus water molecules have an angular geometry. Due to the high difference in the electronegativity difference between oxygen and hydrogen, the oxygen atom with its unshared electrons carries a partial negative charge and the hydrogen atom each carry a partial positive charge. These electrostatic attraction create a diploes and thus the water molecule become polar in nature

3. Ans. (b). Polar molecules can replace water-water interaction with more energetically favourable water-solute interactions

4. Ans. (c). Hydrogen bonding between water molecules

5. Ans. (b). 104.5 o

6. Ans. (b). Hydrogen is less electronegative than oxygen

Electronegativity is the affinity of atomic nuclei towards electrons. Each atom has specific electronegativity values, which means that they have different degree of affinity towards electrons. Oxygen, nitrogen etc. are highly electronegative atoms. The electronegativity of hydrogen is very less. When covalent bond is formed between two atoms, one with high electro-negativity and the other with lesser electronegativity, the paired electron cloud in the covalent bond will shift more towards the highly electro-negative atom and this will create a dipole in the molecule.

7. Ans. (a). 0 o C 100 o C 2260 J/g

Water is an unusual solvent. Water has got high boiling point (100 o C), high melting point (0 o C) and high heat of vaporization (2260 J/g) when compared to other solvents.

Heat of vaporization: The heat energy required to convert 1.0 g of a liquid at its boiling point and at atmospheric pressure into its gaseous state at the same temperature. It is a direct measure of the energy required to overcome attractive forces between molecules in the liquid phase.

8. Ans. (d). 2 δ – charges

Oxygen is highly electronegative than hydrogen, hence oxygen will pull the shared electron pairs in the covalent bond between O and H more towards it an with this oxygen will get a partial negative charge called δ – . Since there are two hydrogen atoms in water molecule, there will be a total of 2δ – charges in a single water molecule. Similarly, each hydrogen in the water molecule will bear one partial positive charge called δ + .

9. Ans. (b). A hydrogen covalently bounded to an electronegative atom and another electronegative atom

10. Ans. (b). 23 kJ/mol

Hydrogen bond is very weak when compared to covalent bonds. Only 23 kJ/mole of energy is required to break the hydrogen bonds in water. This energy input is very less when compared to the requirement of energy to break the O – H covalent bond in water (470 kJ/mol)

11. Ans. (a). Hydrogen bond is 10 % covalent and 90 % electrostatic

Hydrogen bond in water is 10 percent covalent due to the overlaps in the bonding orbitals and 90 percent electrostatic

A single water molecule can form four hydrogen bonds with four different water molecules in liquid water as shown in the figure below

13. Ans. (d) 1 – 20 pico-seconds

Hydrogen bonds in water are highly dynamic. They life span of each hydrogen bond in water is very short. The lifetime of each hydrogen bond is just 1 to 20 picoseconds ( 1 ps = 10-12S)

14. Ans. (a). 470 kJ/mol

15. Ans. (b). 0.177 nm

Malumot: (1). Lehningers Principles of Biochemistry: Chapter: Water
(2). Fundamentals of Biochemistry by Voet and Voet: Chapter: Water

The answer key is prepared with best of our knowledge.
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MCQ on Water, pH and Buffer | Part – 2 | Part – 3 |


Why is hydrogen important to life?

Hydrogen is a part of the water molecular structure.
Water is made of 2 Hydrogen (H) atoms, and 1 Oxygen (O) atom.
Together, they form H2O (water).
Water is essential for all life.

In what other ways Hydrogen is important, I do not know.

It makes up many molecules essential to life.

Tushuntirish:

A prime example of why hydrogen is so important to life is suv. Everybody is familiar with this compound, and it is essential to life, as it helps regulate body processes and also keeps us hydrated. Water has a chemical formula of #H_2O# , and therefore hydrogen is needed to synthesise the compound.

On the other hand, all organic compound that life needs has hydrogen in it. Some examples include #ATP# , #NADPH# , and the #"DNA"# bases just to name a few. Without hydrogen, these compounds wouldn't exist, and we would therefore not live without it.

I don't think pure hydrogen #(H_2)# is essential to life, but if we combine other elements with hydrogen, we get compounds that are required for us to be able to stay alive.


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Importance Of Hydrogen Bonding In Maintaining Protein Structure

When building large structures, one should ponder of how to make sure the structure is long lasting, neat and ready deliver its purpose. In very large structures, creating use of the example of buildings, builders build multiple columns within the ground floor and triangle-like logs on the roof which do not interfere with the buildings’ functionality as well as preventing the building from collapsing. Possessing a column right within the middle of a meeting space would not be appropriate so where these assisting blocks are place should also be wanted to be considered. The similar to patterns are seen in proteins too where bonds shape at specific locations in specific amounts to make the protein tough enough to cope with the jobs they can be doing. These bonds are called the Hydrogen bonds.

Hydrogen bonds are non-covalent meaning they can be created by the electrostatic attractions between positive and negative charged atoms and shape spontaneously without the need for enzyme catalysis 1. Subsequently they can be barely weak so very little no. of life is compulsory to break these bonds. This should be an advantage as well as being a disadvantage, even though structures bonded by hydrogen bonds are not very strong, they can be barely flexible which should be useful when the structure wants to change shape according to its function. This is where proteins return in to play.

Proteins are located everywhere in and between cells, doing so many jobs. They hold an exact 3D shape which directly relates to its function, so there is very many of diversity in proteins but every lone one does an alternate job and do not interfere with each others’. Hydrogen Bonds in Protein Structure. Proteins are synthesized within the cytoplasm of a cell when the codon of mRNA from the nucleus binds with the anti-codon of tRNA which conclusions within the synthesis of amino acids, which are the base units of proteins. Proteins have 4 grades of organisation called the primary, secondary, tertiary and quaternary structure 2.

The primary structure relates to sequence regarding the amino acids, the secondary structure is formed by the alpha helix and the beta sheet, the tertiary structure is the folding regarding the polypeptide chains and quaternary structure is the association of sub units of protein into larger ones. Hydrogen bonds are involved within the secondary, tertiary and the quaternary structure of proteins. How do the amino acids grow to proteins?. Subsequent to the sequence regarding the amino acids are determined, the Alpha helix is formed that is the formation of hydrogen bonds between the C=O and NH groups of amino acids. Then the Beta sheet returns into existence with the formation of hydrogen bonds between different polypeptide chains.

The protein is already becoming a stable structure, with the hydrogen bonds forming at the right spots. Then the polypeptide chains beginning to fold according to where the hydrogen bonds were formed within the secondary structure the hydrogen bonds also play a role in helping the protein hold the shape of its tertiary structure. As the polypeptide chains fold, they need help sequential to be kept at the shape it has taken and repeatedly hydrogen bonds give it, working with other bonds this time, within covalent bonds like disulphide bridges 3. Finally the quaternary structure exists only in proteins that contain higher than one polypeptide. Hydrogen bonds are also located within the quaternary structure.

As we can look hydrogen bonds play a very important role in keeping the shape of proteins. Depending on the primary structure, they shape at specific locations and determine all the other grades of organization of proteins. Without them the tertiary structure should be different meaning the protein cannot bind and interact with the molecules it wants to which should result in a malfunctioning protein. Hydrogen bonds should be likened to match sticks, you can break one with no problems but whether you bring ten of them together they grow to tough and more, even stronger and without functioning proteins we would not be alive!. Biochemistry and Molecular Biology 3rd Ed.


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