Question

a gas mixture at 0°c and 1.0 atm contains 0.010 mol of h₂, 0.015 mol of o₂, and 0.025 mol of n₂. assuming ideal behavior, what is the partial pressure of hydrogen gas (h₂) in the mixture?
a about 0.010 atm, because there is 0.010 mol of h₂ in the sample.
b about 0.050 atm, because there is 0.050 mol of gases at 0°c and 1.0 atm.
c about 0.20 atm, because h₂ comprises 20% of the total number of moles of gas.
d about 0.40 atm, because the mole ratio of h₂:o₂ : n₂ is 0.4 : 0.6 : 1.

Explanation:

Step1: Calculate total moles

$n_{total}=n_{H_2}+n_{O_2}+n_{N_2}=0.010 + 0.015+0.025 = 0.050$ mol

Step2: Use mole - fraction formula for partial pressure

According to Dalton's law of partial pressures, $P_{H_2}=X_{H_2}\times P_{total}$, where $X_{H_2}=\frac{n_{H_2}}{n_{total}}$.
$X_{H_2}=\frac{0.010}{0.050}=0.2$. Given $P_{total} = 1.0$ atm, so $P_{H_2}=0.2\times1.0$ atm $ = 0.20$ atm

Answer:

C. About 0.20 atm, because $H_2$ comprises 20% of the total number of moles of gas.