Lead ions can be precipitated from aqueous solutions by the addition of aqueous iodide:
(aq) +
(aq) →
(s)
Lead iodide is virtually insoluble in water so that the reaction appears to go to completion.How many millilitres of 3.550 mol L^-1 HI(aq) must be added to a solution containing 0.700 mol of
To completely precipitate the lead?

Question

Lead ions can be precipitated from aqueous solutions by the addition of aqueous iodide:

(aq) +

(aq) →

(s)
Lead iodide is virtually insoluble in water so that the reaction appears to go to completion.How many millilitres of 3.550 mol L^-1 HI(aq) must be added to a solution containing 0.700 mol of

To completely precipitate the lead?

Quizplus · Accepted Answer

The balanced chemical equation for this reaction is:

Pb(NO3)2(aq) + 2HI(aq) → PbI2(s) + 2HNO3(aq)

From the equation, we can see that 2 moles of HI are required to completely precipitate 1 mole of Pb(NO3)2. This means that the number of moles of HI required to precipitate 0.7 moles of Pb(NO3)2 is:

0.7 mol Pb(NO3)2 × 2 mol HI/1 mol Pb(NO3)2 = 1.4 mol HI

We can use the molarity of the HI solution to calculate the volume required:

1.4 mol HI × 1 L/3.55 mol = 0.394 L or 394 mL

Therefore, the best choice is (B) 394 mL.

Lead Ions Can Be Precipitated from Aqueous Solutions by the Addition