9. AgBr(s) <==> Ag + (aq) + Br - (aq); Ksp = 1.8 x 10 -13 ----------------(1) Ag
ID: 699923 • Letter: 9
Question
9.
AgBr(s) <==> Ag+(aq) + Br-(aq); Ksp = 1.8 x 10-13 ----------------(1)
Ag+(aq) + 2NH3(aq) <==> [Ag(NH3)2]+ Kf = 1.7 x 107 ----------------(2)
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AgBr(s) + 2NH3(aq) <==> [Ag(NH3)2]+(aq) + Br-(aq); Kc = Ksp x Kf
So,
Kc = (1.8 x 10-13) x (1.7 x 107)
= 3.06 x 10-6
But,
Kc = [Ag(NH3)2+] [Br-] / [NH3]2
3.06 x 10-6 = (x)(x) / (0.5 - 2x)2
3.06 x 10-6 = x2 / (0.5)2
x2 = (3.06 x 10-6) x (0.25)
x2 = 7.65 x 10-7
x = 8.75 x 10-4
So, answer is option (A) 8.7 x 10-4 M
10.
ZnCO3 will dissociate as follows;
ZnCO3 <==> Zn2+ + CO32-(aq);
When Na2CO3 is added, it will dissociate as follows;
Na2CO3 <==> 2 Na+ + CO32-(aq);
So, more CO32-(aq) formed will react with Zn2+ to produce back ZnCO3.
So, answer is option (B) Na2CO3.
Explanation / Answer
solubility of the slightly soluble salt The solubility of AgCl is the same in a 1.0 M NH, solution vs. in pure water because the Ksp of AgCl is a constant at 25°C. D) 9. Calculate the molar solubity of AgBrts) in 0.500 M NH, at 25°C. Kup of AgBr is 1.8 x 10-5, K of Ag(NHs)2" is 1.7 x 10 A) 8.7 x 104 M B) 1.2x 10-3 M C) 4.2 x 10-7 M D) 7.7 x 10-7 M 10. Which of the following compounds, when added to a saturated solution of zinc carbonate, will decrease the solubility of zinc carbonate? Kap of ZnCOs is 1.0 x 10-10, K of Zn(CN) is 4.2x 1019 A) HIl(aq) B) Na COs(a) C) NaCN(aq) D) NaCl(aq)
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