Answer to Question #184156 in General Chemistry for JIO

Question

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A weak acid, HZ, has a K_a value of 6.52 x 10^-5.

(a) Write the reaction of HZ with water. 

(b) Write the equilibrium expression for the reaction of HZ with water.

(c) Calculate the pH of a 0.150 M solution of HZ. 

(d) The Y^- ion reacts with water to form HY and hydroxide ion, as shown in the following equation.

Y^- (aq) + H2O (l) ⇌ HY (aq) + OH^- (aq)

Given that [OH^-] is 1.77 x 10^-5 M in a 0.480 M solution of NaY, calculate each of the following:

(i) The value of K_b for the Y^- ion. 

(ii) The value of K_a for HY. 

(e) Which acid, HZ or HY, is stronger? Justify your answer

Answer 1

a).

$HZ + H_2O ==> H3O^+ + Z^-$

b)

$HZ_{aq} + H2O_ {l} ⇌ H3O^+_{aq}+ Z^- _{aq}$ $K_a = 2.9 × 10^{-8}$

PH = -log(0.150)

PH = 0.8