Question

A gas cylinder contains 2.0 mol of gas X and 6.0 mol of gas Y at a total pressure of 2.1 atm. What is the partial pressure of gas Y?
Use mc017-1.jpg.
0.50 atm
1.6 atm
2.1 atm
2.8 atm

Answer 1

Partial pressure  = mole fraction x Total pressure

mole fraction of Y = 6/8 = 3/4 = 0.75

Partial pressure of Y = 0.75 x 2.1 = 1.575 atm = 1.6 atm ( rounding off to 1 decimal)

Answer 2

Answer: 1.6 atm is the partial pressure of gas Y.

Solution:

According Dalton's law of partial pressure :

$p_A=p_T\times X_A$

where $p_A=\text{partial pressure of component A}$

$p_T= \text{total prssure}$

$X_A=\text{mole fraction of A}$

According to question:

Mole fraction of Y, $X_Y=\frac{6}{6+2}=\frac{6}{8}$

Total pressure $p_T$ = 2.1 atm

$p_Y=p_t\times X_Y=2.1\times \frac{6}{8}$

$p_Y=1.57 atm$

The partial pressure of gas Y is 1.57 atm $\approx$ 1.6 atm.