4241HW02K_S11

# 4241HW02K_S11 - 3-]/[H 2 CO 3 ] = [H + ] 2 /[H 2 CO 3 ] =...

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GLY 4241 HOMEWORK 2 Acid-Base Reactions 1. Given a solution of 0.0001M H 2 CO 3 . The first ionization constant of carbonic acid is 10 -6.4 , and the second ionization constant is 10 -10.3 . a). Calculate the hydrogen-ion concentration. b). Calculate the pH. c). Also calculate what fraction of the H 2 CO 3 has been dissociated. d). Compare this fraction with the fraction dissociated when the concentration is 0.01M (given that the pH is 4.2 in a 0.01M solution). e). What generalization can you make regarding the effect of dilution on the degree of dissociation? \4241\HOMEWORK\4241HW02_S11.wpd February 4, 2011

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Homework 2 Answer Sheet Problem 1. Assume the following: 3 1-a [H 2 CO 3 ] >> [CO 3 2- ] [HCO 3 - ] >> [CO 3 2- ] [H + ] >> [OH - ] Then [H + ] = [HCO 3 - ] [H + ][HCO
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Unformatted text preview: 3-]/[H 2 CO 3 ] = [H + ] 2 /[H 2 CO 3 ] = 10-6.4 and [H 2 CO 3 ] + [H + ] = 0.0001M If [H 2 CO 3 ] >> [H + ] then [H 2 CO 3 ] = 0.0001M [H + ] 2 = 10-6.4 x 0.0001 = 4.0 x 10-11 [H + ] = 6.3 x 10-6 = 10-5.2 1 1-b pH = -log (-5.2) = 5.2 2 1-c The percent ionized may be calculated by dividing the hydrogen ion concentration by the concentration of the solution and multiplying by 100. % ionized = (10-5.2 )/(10-4 ) = 10-1.2 = 0.06 x 100 = 6% 2 1-d At a concentration of 0.01M, pH = 4.2 % ionized = (10-4.2 )/(10-2 ) = 10-2.2 = 0.006 x 100 = 0.6% 2 1-e In general we may conclude that there is more ionization in a dilute solution. Numbers to the left in red are the possible points....
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4241HW02K_S11 - 3-]/[H 2 CO 3 ] = [H + ] 2 /[H 2 CO 3 ] =...

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