Kabir drops 13 g of zinc into a solution that holds 7.3 g of hydrogen chloride: Zn + 2HCl → ZnCl₂ +…

Step 1. Moles. Zinc: $\dfrac{13}{65} = 0.2\ \text{mol}$. Hydrogen chloride: $\dfrac{7.3}{36.5} = 0.2\ \text{mol}$.

Step 2. Shares. Zinc: $\dfrac{0.2}{1} = 0.2$. Hydrogen chloride: $\dfrac{0.2}{2} = 0.1$. Hydrogen chloride is the limiting reagent.

Step 3. Hydrogen. $0.1\ \text{mol}$, which is $0.2\ \text{g}$, and $0.1 \times 22.7 = 2.27\ \text{L}$ at STP.

Step 4. Zinc left. $0.1\ \text{mol}$ reacts, so $0.1\ \text{mol}$ is left: $0.1 \times 65 = 6.5\ \text{g}$.