Dissolving 1.24 g of white phosphorous in boiling NaOH solution in an inert atmosphere gives a gas Q . The amount of CuSO₄ (in g) required to completely consume the gas Q is _______.
[Given: Atomic mass of H = 1, O = 16, Na = 23, P = 31, S = 32, Cu = 63]

Correct Answer: The correct answer is 2.38 (or 2.38 g).

Step-by-Step Explanation:

Step 1: Reaction of white phosphorus with boiling NaOH solution
When white phosphorus (${\text{P}}_4$) is heated with a boiling sodium hydroxide ($\text{NaOH}$) solution in an inert atmosphere, phosphine gas (${\text{PH}}_3$) is evolved along with sodium hypophosphite (${\text{NaH}}_2{\text{PO}}_2$). Thus, gas Q is phosphine (${\text{PH}}_3$).

The balanced chemical equation for this reaction is:

${\text{P}}_4+3\text{NaOH}+3{\text{H}}_2\text{O}\to {\text{PH}}_3+3{\text{NaH}}_2{\text{PO}}_2$

From the stoichiometry of the reaction:
1 mole of ${\text{P}}_4$ produces 1 mole of ${\text{PH}}_3$ gas.

Step 2: Calculate the moles of white phosphorus (${\text{P}}_4$) and gas Q (${\text{PH}}_3$)
Molar mass of ${\text{P}}_4$ = 4 × 31 g/mol = 124 g/mol.
Given mass of ${\text{P}}_4$ = 1.24 g.

$\text{Moles of}{\text{P}}_4=\frac{1.24\text{g}}{124\text{g/mol}}=0.01\text{mol}$

Since 1 mole of ${\text{P}}_4$ gives 1 mole of ${\text{PH}}_3$:
Moles of gas Q (${\text{PH}}_3$) produced = 0.01 mol.

Step 3: Reaction of phosphine (${\text{PH}}_3$) with copper sulfate (${\text{CuSO}}_4$)
Phosphine gas reacts with copper sulfate solution to form cupric phosphide (${\text{Cu}}_3{\text{P}}_2$) precipitate and sulfuric acid (${\text{H}}_2{\text{SO}}_4$).

The balanced chemical equation is:

$3{\text{CuSO}}_4+2{\text{PH}}_3\to {\text{Cu}}_3{\text{P}}_2+3{\text{H}}_2{\text{SO}}_4$

From the balanced equation:
2 moles of ${\text{PH}}_3$ require 3 moles of ${\text{CuSO}}_4$ for complete consumption.

Step 4: Calculate the moles and mass of ${\text{CuSO}}_4$ required
Moles of ${\text{CuSO}}_4$ required = $\frac{3}{2}\times \text{Moles of}{\text{PH}}_3$

$\text{Moles of}{\text{CuSO}}_4=\frac{3}{2}\times 0.01=0.015\text{mol}$

Now, calculate the molar mass of ${\text{CuSO}}_4$:
Molar mass of ${\text{CuSO}}_4$ = 63 + 32 + (4 × 16) = 63 + 32 + 64 = 159 g/mol.

Mass of ${\text{CuSO}}_4$ required = Moles × Molar mass:

$\text{Mass of}{\text{CuSO}}_4=0.015\text{mol}\times 159\text{g/mol}=2.385\text{g}\approx 2.38\text{g}$

Therefore, the amount of ${\text{CuSO}}_4$ required to completely consume the gas Q is 2.38 g.