Question

How much oxygen is dissolved in $100\, mL$ water at $298\, K$ if partial pressure of oxygen is $0.5\, atm$ and $K_H = 1.4 \times 10^{-3}\, mol/L/atm$ ?

• A. $22.4 \,mg$
• B. $22.4\, g$
• C. $2.24 \,g$
• D. $2.24 \,mg$

Answer 1

Answer: (D)

$2.24 \,mg$

Answer 2

According to Henry?? law, $s = K_H \times p$, where s is concentration of $O_2$ dissolved. $s = 1.4 \times 10^{-3} \times 0.5$ $= 0.7 \times 10^{-3}\,mol/L$ $s = \frac{n}{V}$ or $n = 0.7 \times 10^{-3} \times 0.1$ $= 0.7 \times 10^{-4}\,mol$ $n = \frac{w}{M}$ or $w = n \times M$ $= 0.7 \times 10^{-4} \times 32$ $= 22.4 \times 10^{-4}\, g$ or $2.24\, mg$