Question

$0.9$ g of Aluminium reacts with dil. $HCl$ to give $H_2$. The volume of $H_2$ evolved at STP is:

(Atomic weight of $Al=27$)

• A. $1.12$ litres
• B. $2.24$ litres
• C. $3.33$ litres
• D. $4.44$ litres

Answer 1

The correct option is A $1.12$ litres

The Molar Volume, represented by Vm, is the volume occupied by one mole of a substance which can be a chemical element or a chemical compound at Standard Temperature and Pressure (STP). It can be calculated by dividing Molar mass (M) by mass density (ρ). One mole of any gas at a particular temperature and pressure has fixed volume and known as its Molar gas volume.

The balanced chemical reaction is

$2Al+6HCl\to 2AlC{l}_3+3H_2$

Now given 0.9g of aluminum. Therefore moles of aluminum $=\frac{0.9}{27}=\frac{1}{30}$.

Apply unitary method and solve:

2 mol Al gives 3 mol $H_2$

Then $\frac{1}{30}$ mol Al will give $=\frac{3}{2}\times \frac{1}{30}$

$=\frac{1}{20}mol{H}_2$.

Now convert mol to volume.

V $=\frac{1}{20}\times 22.4L$

$=1.12L.$