Question

Henry's law constant of Oxygen is 1.4 * 10-3 mol L-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] 22.4mg [d] 2.24 mg [ e] 3.2 mg

Answer 1

When the partial pressure of oxygen is 0.5 atm, then [b] 3.2 g oxygen is dissolved in 100ml at 298 K

Answer 2

Answer: The correct option is (d).

Explanation:

Solubility of gas = $C_{O_2}$

Henry constant of gas ,k= $1.4\times 10^{-3} mol /L atm$  

partial pressure ,$P_{O_2}=0.5 atm$

According to Henry's law -

$C_g=k\times P_g$

$C_{O_2}=1.4\times 10^{-3} mol /L atm\times 0.5 atm=0.7\times 10^{-3} mol /L atm$  

1 L of solution contains = $0.7\times 10^{-3}$ moles of oxygen

0.1 L (100 mL) contains = $0.7\times 10^{-3}\times 0.1$ moles of oxygen

Mass of oxygen gas dissolved = moles × molecular mass

$0.7\times 10^{-3}\times 0.1 L\times 32g/mol = 2.24\times 10^{-3} g=2.24 mg$

(1g=1000 mg)

2.24 mg of oxygen gas is dissolved in 1oo grams of water.Hence, the correct answer is option d.