Question

How many litres of ammonia gas at S.T.P. would be needed to prepare $100ml$ of $2.5M$ ammonium hydroxide solution ?

• A. 5.6 L
• B. 0.056 L
• C. 11.2 L
• D. 0.56 L

Answer 1

Answer: (A)

Molecular weight of $N{H}_{4}OH=35$

Now, $35g$ of $N{H}_{4}OH$ is needed to prepare $1M$ solution in 1 litre

$\Rightarrow 35gN{H}_{4}OH$ in 1 L solution $\equiv$ 1 molar solution

$\Rightarrow$ $2.5\times 35gN{H}_{4}OH$ in 1 L solution $\equiv 2.5$ molar solution

$\Rightarrow \frac{2.5\times 35}{10}gN{H}_{4}OH$ is $100mL$ solution $\equiv 2.5$ molar solution

$\Rightarrow 8.75gN{H}_{4}OH$ was dissolved.

$N{H}_3+H_{2}O\to N{H}_{4}OH$

For $35gN{H}_{4}OH,N{H}_3$ needed $=22.4L$ at S.T.P

$\Rightarrow$ for $8.75g$ $N{H}_{4}OH,N{H}_3$ needed $=\frac{22.4}{35}\times 8.75$ L

$=5.6L$