Question

a flask contains 0.25 mole of so₂(g), 0.50 mole of ch₄(g), and 0.50 mole of o₂(g). the total pressure of the gases in the flask is 800 mm hg. what is the partial pressure of the so₂(g) in the flask?
a 600 mm hg
b 250 mm hg
c 200 mm hg
d 160 mm hg

Explanation:

Step1: Calculate the mole fraction of $SO_2$

The total number of moles $n_{total}=0.25 + 0.50+0.50 = 1.25$ moles. The mole fraction of $SO_2$, $X_{SO_2}=\frac{n_{SO_2}}{n_{total}}=\frac{0.25}{1.25}= 0.2$.

Step2: Calculate the partial pressure of $SO_2$

According to Dalton's law of partial pressures, $P_{SO_2}=X_{SO_2}\times P_{total}$. Given $P_{total} = 800$ mm Hg, so $P_{SO_2}=0.2\times800$ mm Hg = 160 mm Hg.

Answer:

D. 160 mm Hg