Question

How many litres of ammonia gas at S.T.P. would be needed to prepare $100\, ml$ of $2.5\, M$ 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 $NH_4OH = 35$

Now, $35 \,g$ of $NH_4OH$ is needed to prepare $1\, M$ solution in 1 litre

$\Rightarrow 35 \,g \,NH_4OH$ in 1 L solution $≡$ 1 molar solution

$\Rightarrow $ $2.5×35\, g \,NH_4OH$ in 1 L solution $≡ 2.5$ molar solution

$\Rightarrow \frac{2.5\times35}{10}\, g \,NH_{4}OH$ is $100 \,mL$ solution $≡ 2.5$ molar solution

$\Rightarrow 8.75 \,g \,NH_{4}OH$ was dissolved.

$NH_{3} + H_{2}O \to NH_{4}OH$

For $35 \,g \,NH_{4}OH, NH_{3}$ needed $= 22.4\, L$ at S.T.P

$\Rightarrow $ for $ 8.75\, g$ $NH_{4} OH, NH_{3}$ needed $= \frac{22.4}{35}\times8.75$ L

$= 5.6 \,L$