CHM116 week 3 Mon probs

# CHM116 week 3 Mon probs - CHM116 week 3 Mon 9/13 problems 1...

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1. CHM116 week 3 Mon 9/13 problems Like all equilibrium constants, the value of K w depends on temperature. At body temperature (37 ºC), K w = 2.4 x 10 -14 . What is the pH of pure water at body temperature? 2. You can see from problem #1 that K w increases with temperature. Is the autoionization of water endothermic or exothermic? Explain with a sentence. 3. A 0.115 M solution of a generic weak acid (HA) has a pH of 3.29. Calculate the acid dissociation constant ( K a ) for the acid. 4. What would the K b for the conjugate base of the acid HA in #3 above be? 5. Caffeine (C 8 H 10 N 4 O 2 ) is a weak base with a p K b of 10.4. If the smallest brewed coffee from Starbucks is 200 mL and contains 200 mg of caffeine, what would you predict the pH to be if no other coffee components affected pH? (the MW of caffeine is 194.2 g/mole)

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Carbon dioxide levels in the atmosphere have increased about 20% over the last century. Since the Earth’s oceans are exposed to atmospheric CO 2 , what effect might the increased levels have on the pH of the world’s oceans? How might this affect limestone structures like coral reefs or the many sea creatures whose shells
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