Question

A 4.5 mol sample of acetylene gas has a volume of 18 L at 25°C. atm×L2 L

a=4.453 mol2 b=0.05220 mol

i. Calculate the pressure using the Ideal Gas Law.

ii. Calculate the corrected pressure using the Van der Waals Equation.

Answer 1

Solution.

I) Using the Ideal Gas Equation

V = 18 L;

n = 4.5 mol;

T = 298 K;

PV = nRT;

R = 0.0821 L atm K^-1 mol^-1.

P = nRT/V = (4.5 x 0.0821 x 298)/18= 6.12 atm;

II)Using Van der Waals equation

a =4.453 L² atm mol^-2;

b = 0.05220 L mol^-1;

(P + an²/V²)(V - nb) = nRT;

(P + 4.453x(4.5)²/18²)(18-4.5 x0.05220)=4.5x 0.0821 x 298;

(P + 0.28)x17.77=110.1;

P + 0.28=6.20;

P=6.20-0.28=5.92 atm.

Answer: I) P=6.12 atm;

              II) P=5.92 atm.