Question

Oxygen gas having a volume of 1080 cm³ at 22.5°C and 1.01 x 10⁵ Pa expands until its volume is 1550 cm³ and its pressure is 1.10 x 10⁵ Pa. Find (a) the number of moles of oxygen present and (b) the final temperature of the sample.

Answer 1

(a)

Ideal gas law:

pV= nRT

Here,

n= number of moles

p = absolute pressure = 1.01× 10⁵ pa

V= volume = 1080 cm³= 0.001080 m³

R = Gas constant = 8.314472 J/mol-K

T = absolute temperature in K = 22.5+273 = 295.5 K

n = PV/RT= (1.01× 10⁵)(0.001080)/(8.314472)(295.5)

n = 0.044 moles

(b)

Expansion from state 1 to state 2

p₁V₁/T₁ =p₂V₂/T₂

T₂= p₂V₂T₁/p₁V₁

= (1.10×10⁵)(0.001550)(295.5)/ (1.01× 10⁵)(0.001080)

= 461.88 K = 188.88 °c