The solubility of O2 in water at 298 K is 1.3x10^-3 mol L^-1 atm^-1 (concentration =k_H p). Air contains 21% O2 by volume at 1.0 atm. Find the mass of O2 (molar mass 32 g mol^-1) dissolved in 2.0 L of water at equilibrium with air. Give the answer in mg to one decimal place.

JEE Main levelNumerical answerDifficulty 2 of 3so126

The solubility of $O X_{2}$ in water at $298 K$ is $1.3 \times 1 0^{- 3} mol L^{- 1} at m^{- 1}$ (concentration $= k_{H} p$ ). Air contains $21%$ $O X_{2}$ by volume at $1.0$ atm. Find the mass of $O X_{2}$ (molar mass $32 g mo l^{- 1}$ ) dissolved in $2.0$ L of water at equilibrium with air. Give the answer in mg to one decimal place.

Numerical answer type, answer in mg, tolerance 0.1.

Partial pressure of

O X_{2}

0.21

atm. Concentration

= 1.3 \times 1 0^{- 3} \times 0.21 = 2.73 \times 1 0^{- 4}

mol/L. Moles in 2.0 L

= 5.46 \times 1 0^{- 4}

mol, mass

= 5.46 \times 1 0^{- 4} \times 32 = 0.01747

= 17.5

mg.