Question

4. Calculate the equilibrium concentration of Ag⁺ (aq) in a solution that is initially 0.150 M AgNO₃ and 0.500 M KCN. The formation constant for [Ag(CN)₂]^- (aq) is K_f= 1.0 x 10²¹

a. 8.9 x 10^-21 M

b. 2.3 x 10 ^-21 M

c. 4.3 x 10 ^-22 M

d. 7.5 x 10 ^-22 M

e. 3.8 x 10 ^-21 M

5. If a solution of Pb(NO₃)₂ (aq) is mixed with a solution of NaBr(aq), what condition would cause precipitation of PbBr₂ (s) to occur?

a. When [Na⁺][NO₃^-] < K_sp for PbBr₂

b. When [Pb²⁺][Br ^-]² < K_sp for PbBr₂

c. When [Pb²⁺][Br ^-] < K_sp for PbBr₂

d. When [Pb²⁺][Br ^-]² > K_sp for PbBr₂

e. When [Pb²⁺][Br ^- ] > K_sp for PbBr₂

Answer 1

Ag⁺ (aq) + 2CN^- (aq) = [Ag(CN)₂]^- (aq)

FORMATION CONSTANT K =[ [Ag(CN)₂]^- (aq)] /[ Ag⁺ (aq) ] [CN^- (aq)]²

                                    Ag⁺ (aq)    + 2CN^- (aq)    =        [Ag(CN)₂]^- (aq)

INTIAL CONCENTRATION         0.150 M                 0.500 M                         0

LET AT EQUILIBRIUM               (.150-X)               (.500-2X)                         X

X M Ag⁺ (aq) REACTES

FORMATION CONSTANT K =[ [Ag(CN)₂]^- (aq)] /[ Ag⁺ (aq) ] [CN^- (aq)]²

       K = X / (.150-X ) (.500-X )²

^NOW SOLVE THE EQUATION TO GET X

5. d. When [Pb²⁺][Br ^-]² > K_sp for PbBr₂