A gaseous compound of nitrogen and hydrogen contains (by mass) of hydrogen. The vapour density of th — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question
Question
A gaseous compound of nitrogen and hydrogen contains $12.5\%$ (by mass) of hydrogen. The vapour density of the compound relative to hydrogen gas ($H_2$) is $16$. Which of the following statements is/are chemically correct?
💡 Solution & Explanation
Step 1: Determine molar mass. Molar mass = $2 \times V.D. = 2 \times 16 = 32\text{ g/mol}$ (Option B is true). Step 2: Find empirical formula. %N = $100 - 12.5 = 87.5\%$. Moles N = $87.5 / 14 = 6.25$. Moles H = $12.5 / 1 = 12.5$. Ratio N:H = $1:2$. Empirical formula is $NH_2$ (Option A is true). Step 3: Find molecular formula. Empirical mass = $14 + 2 = 16$. n = $32 / 16 = 2$. Molecular formula = $(NH_2)_2 = N_2H_4$ (Option C is true). Step 4: V.D. relative to He = $\frac{M_{\text{substance}}}{M_{He}} = \frac{32}{4} = 8$ (Option D is true).