, a toxic gas with rotten egg like smell, is used for the quantitative analysis. If the solubility o — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Molality = 0.2 m means 0.2 moles of $\text{H}_2\text{S}$ in 1 kg (1000 g) of water. Moles of water = $1000 / 18 = 55.55 \text{ mol}$. Mole fraction $x = 0.2 / (0.2 + 55.55) \approx 0.2 / 55.75 = 0.003587$. At STP, pressure $p = 1 \text{ bar} = 10^5 \text{ Pa}$. $K_H = p / x = 10^5 / 0.003587 \approx 2.78 \times 10^7 \text{ Pa}$. Therefore, correct answer is D.