IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

konichiwa2x

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.

subs

1 >>> c
2 >>> b
3 >>> d

amangem

1. a and b contain a common ion . this wud decrease the ionisation of the salt and thus solubility

2. zn2+ is only ppt in basic medium . ksp of zns is as such

3. nahco3 is acidic as well . thus it cant exist simultanmeously with naoh

konichiwa2x

1. yes i understood it A and B have a common ion so they can be eliminated. But how do I know whether C is correct or D?

2. thanks

3. Oh, so they will neutralise each other. ok that makes sense. thanks! can u explain question 1 a bit more clearly?

amangem

see here

with the first part that is c lead nitrate will be formed which is soluble . thus the equilibrium will shift towards the right

deepu_0088

1---c
2---d
3---a

vkvashistha

A. You have misconception about "Common Ion Effect" dear, it is only applicable for weak electrolyte. and lead Iodide is not a weak electrolyte. rather it almost fully dissociate. So we can't apply this concept. Vont't hoff factor... remeber....check von't hoff factor in all four options and correct you answer. Solubility also depend on H-bonding , the compund in which H-bonding is there have more solubilty.

B. Ag(ion) is correct as it comes in first group in basic radicals which gives white ppt. when it is treated with HCl only.

C. By meaning Existing together , I can't understand.....

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