Question

Henry's law constant of oxygen is $1.4 \times 10^{-3} mol 1^{-1} atm ^{-1}$ at $298\, K$. How much of oxygen is dissolved in $100\, ml$ at $298 \,K$ when the partial pressure of oxygen is 0.5 atm?

• A. 1.4 g
• B. 3.2 g
• C. 2.24 mg
• D. 22.4 mg

Answer 1

Answer: (C)

$C = K _{ H } \cdot P _{ O _{2}}$

$=1.4 \times 10^{-3} \times 0.5=7 \times 10^{-4} mol / L$

$\therefore $ Number of moles of oxygen dissolved in $1000 \,ml$

$=7 \times 10^{-4}$

$\therefore $ Number of moles of oxygen dissolved in $100 ml$

$=\frac{7 \times 10^{-4} \times 100}{1000}=7 \times 10^{-5}$

$\therefore $ Weight of oxygen in $100 \,ml$

$=7 \times 10^{-5} \times 32$

$=2.24 \times 10^{-3} g =2.24 \,mg$