Dalton\'s law states that the total pressure. P_total, of a mixture of gases in

Question

Dalton's law states that the total pressure. P_total, of a mixture of gases in a container equals the sum of the pressures of each individual gas: P_total = P_1 + P_2 + P_3 + ... The partial pressure of the first component, P_1, is equal to the mole fraction of this component, X_1, times the total pressure of the mixture: P_1 = X_1 times P_total The mole fraction, X, represents the concentration of the component in the gas mixture, so X_1 = moles of component 1/total moles in mixture Express the pressure values numerically in atmospheres, separated by commas. Enter the partial pressure of methane first, then ethane, then propane. A gaseous mixture of O_2 and N_2 contains 38.8 % nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 365 mmHg? Express you answer numerically in millimetres of mercury.

Explanation / Answer

b]

If the mixture contains 38.8 % nitrogen by mass it will contain l00%-38.8 or 61.2% by mass oxygen.

Lets just say we have l00 grams of this gas mixture.

In that case we would have 38.8 g Nitrogen and 61.2 grams oxygen

now get these masses into moles.

38.8 g N2 over 28g/mole = 1.385 moles N2

and 61.2 g oxygen over 32 g/mole = 1.9125 moles O2

Now get total moles gas, 1.385 + 1.9125 = 3.3 total moles in gas mixture

now get partial pressures like we did before using mole fractions of each gas.

Mole fraction N2 = 1.385 moles N2 / 3.3 total moles gas = 0.4196

Mole fraction O2 = 1.9125 moles O2 / 3.3 total moles gas = 0.578

Now get partial pressure of each gas by multiplying its mole fraction times total pressure of 365 mm

and Partial pressure O2 = .578 * 365 mm= 210.97 mm Hg

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