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Date: 26-7-2016
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Date: 12-4-2017
1397
Date: 25-1-2017
1307
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Nonpolar Gases Are Poorly Soluble in Water
The molecules of the biologically important gases CO2, O2, and N2 are nonpolar. In O2 and N2, electrons are shared equally by both atoms. In CO2, each CUO bond is polar, but the two dipoles are oppositely directed and cancel each other (Table 1.1). The movement of molecules from the disordered gas phase into aqueous solution constrains their motion and the motion of water molecules and therefore represents a decrease in entropy. The nonpolar nature of these gases and the decrease in entropy when they enter solution combine to make them very poorly soluble in water (Table 1.1). Some organisms have water-soluble carrier proteins (hemoglobin and myoglobin, for example) that facilitate the transport of O2. Carbon dioxide forms carbonic acid (H2CO3) in aqueous solution and is transported as the HCO3- (bicarbonate) ion, either free bicarbonate is very soluble in water (~100 g/L at 25 οC) or bound to hemoglobin. Two other gases, NH3 and H2S, also have biological roles in some organisms; these gases are polar and dissolve readily in water.
TABLE 1.1 Solubilities of Some Gases in Water
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إجراء أول اختبار لدواء "ثوري" يتصدى لعدة أنواع من السرطان
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دراسة تكشف "سببا غريبا" يعيق نمو الطيور
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اللجنة التحضيرية للمؤتمر الحسيني الثاني عشر في جامعة بغداد تعلن مجموعة من التوصيات
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السيد الصافي يزور قسم التربية والتعليم ويؤكد على دعم العملية التربوية للارتقاء بها
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لمنتسبي العتبة العباسية قسم التطوير ينظم ورشة عن مهارات الاتصال والتواصل الفعال
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في جامعة بغداد.. المؤتمر الحسيني الثاني عشر يشهد جلسات بحثية وحوارية
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