[xstrae]

Hi,

Can you please help me out with these questions?

1. Lead Iodide will have maximum solubility in
(A) 0.1 Pb(NO_3/)₂ (B) 0.2 M NaI (C) 0.2 Na(NO_3/)₂ (D)  0.1 Ba₃(PO_4/)₂

I thoguht that it wont be (A) or (B) PBI2 wont dissasociate as much in these due to common ion effect. But how do I know whether it is (C) or (D)?

2. Which ion cannot be precipitated by HCl and H₂S?
(A) Pb²⁺ (B) Ag⁺  (C) Cu²⁺  (D) Zn²⁺

3. The pair of compounds which cannot exist together in solutions:
(A) NaHCO₃ and NaOH
(B) Na₂CO₃ and NaHCO₃
(C) Na₂CO₃ and NaOH
(D) NaHCO₃ and NaCl

thanks for your time.

[Yggdrasil]

1. Lead Iodide will have maximum solubility in
(A) 0.1 Pb(NO_3/)₂ (B) 0.2 M NaI (C) 0.2 Na(NO_3/)₂ (D)  0.1 Ba₃(PO_4/)₂

I thoguht that it wont be (A) or (B) PBI2 wont dissasociate as much in these due to common ion effect. But how do I know whether it is (C) or (D)?

You are absolutely correct about (a) and (b).  To distinguish between (c) and (d) consider the following question:  will any of these salts remove lead or iodide ions from solution by precipitating them?  Would this have an effect on the solubility of lead iodide?

2. Which ion cannot be precipitated by HCl and H₂S?
(A) Pb²⁺ (B) Ag⁺  (C) Cu²⁺  (D) Zn²⁺

Two you can immediately rule out because the ions are precipitated by HCl?  I'm not sure how to distinguish between the remaining two, however.

3. The pair of compounds which cannot exist together in solutions:
(A) NaHCO₃ and NaOH
(B) Na₂CO₃ and NaHCO₃
(C) Na₂CO₃ and NaOH
(D) NaHCO₃ and NaCl

One reason why two compounds cannot exist together in solution is if they react with each other.