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The following pictures represent aqueous solutions of binary acids of the type H

ID: 514597 • Letter: T

Question

The following pictures represent aqueous solutions of binary acids of the type HA where the water molecules have been omitted for clarity. Determine the strongest acid of the set. A) A B) B C) C D) D What is the pH of a 0.020 M HClO_4 solution? HCLO_4(aq) rightarrow H^+ (aq) + ClO_4(aq) HClO_4 (aq) is a strong acid A) 1.70 B) 0.040 C) 12.30 D) 0.020 What is the equilibrium constant expression (K_a) for the acid dissociation of hydrocyanic acid HCN? The equation of interest is HCN (aq) + H_2O (l) H_3O^+ (aq) + CN^- (aq) A) K_a = ([HCN][H_2O])/([H_3O^+][CN^+]) B) K_a = ([H_3O^+][CN^+])/([HCN][H_2O]) C) K_a = ([H_3O^+][CN^+])/([HCN]) D) K_a = ([HCN])/([H_3O^+][CN^-])

Explanation / Answer

1)The strongest acid of the set is D) D

As D has all HA , which is a strongest among the rest and can easily dissociate to H+ and A-.

2) pH of 0.020 M HClO4 solution is A) 1.70

pH= - log (H+)

pH= -log(0.020)

pH= 1.69 = 1.70

3)The equilibrium dissociation constant expression Ka for acid dissociation of HCN is C) Ka= (H3O+)(CN-)/(HCN)

Ka is represented in terms of products to reactant as

Ka= ( H+)(A-)/ (HA)