Question

$H_2S$ is a toxic gas used in qualitative analysis. If solubility of $H_2S$ in water at $STP$ is $0.195\, m$, what is the value of $K_H$ ?

• A. $0.0263 \,bar$
• B. $69.16 \,bar$
• C. $192 \,bar$
• D. $282 \,bar$

Answer 1

Answer: (D)

$282 \,bar$

Answer 2

No. of moles of $H_2S = 0.195$ No. of moles of $H_{2}O = \frac{1000}{18} = 55.55\,mol$ Mole fraction of $H_{2}S =\frac{0.195}{0.195 + 55.55} = 0.0035$ Pressure at $STP = 0.987$ bar According to Henry?? law, $p = K_{H}x$ or $K_{H} = \frac{p_{H_2S}}{x_{H_2S}}= \frac{0.987}{0.0035}$ $= 282\,$bar