please answer question 140. Also if it needs more info, please tell me what its

Question

please answer question 140.
Also if it needs more info, please tell me what its missing

formation, calc 0.50 m Nal salution. (b) What is the freezing from this point after the addition of sufficient Hg an in- soluble compound, to the solution to react with all ted with the free 1 ions in solution? Assume volume to rezna in constant. re salt 16.140 Calcallare the maximum mass (in grams) of each of the as soluble salts that can be added to 200 ml of 0.100 M MgCl2 without causing a precipitate to fona: (a) NazCOI, (b) AgNO (c) KOH. Assume volume to remain constant. 16.141 A 1.0-L saturated silver carbonate solution at 5 is treated with enough hydrochloric acid to decom- pose the compound. The carbon dioxide generated is collected in a 19-mL vial and exerts a pressure of 114 mmHg at 25 C, What is the K n of Ag CO1

Explanation / Answer

140)

(a) Ksp of MgCO3 = 6.82 x 10^-6

Ksp = [Mg2+][CO3^2-]

[Mg2+] = 0.1 M

so,

[CO3^2-] needed for precipitation = 6.82 x 10^-6/0.1 = 6.82 x 10^-5 M

Na2CO3 to be added for precipitation = 6.82 x 10^-5 M x 0.2 L x 106 g/mol

                                                             = 1.45 mg

So, any amount below 1.45 mg of Na2CO3 would not cause precipitation of MgCO3

(b) With AgNO3

No precipitate is formed.

Mg(NO3)2 is soluble

(c) Ksp of Mg(OH)2 = 1.8 x 10^-11

Ksp = [Mg2+][OH-]^2

so,

[OH-] needed for precipitation = sq.rt.(1.8 x 10^-11/0.1) = 1.34 x 10^-5 M

KOH to be added for precipitation = 1.34 x 10^-5 M x 0.2 L x 56.1 g/mol

                                                      = 0.15 mg

So, any amount below 0.15 mg of KOH would not cause precipitation of Mg(OH)2

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