Question

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

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

Answer 1

Answer: (D)

According to Henry’s 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 $2.24mg$