Answer to Question #226639 in English for Zee

Question

Oxygen (molar mass 32 kg/kmol) expands reversibly in a cylinder behind a piston at a constant pressure of 3 bar. The volume initially is 0.0114 m³ and finally is 0,0319m³ , the initial temperature is 16.38⁰C. Calculate the absolute temperature after expansion with the correct unit. Assume oxygen to be a perfect gas and take the specific heat at constant pressure as = 0.917kj/kgK.

Answer 1

molar mass = 32 kg/kmol

P = constant

P = 3 bar

V₁ = 0.01m³                  V₂ = 0.03m³

TI= 17⁰C  = 290.15K

W = ?

Q = ?

Constant Pressure (Cp) = 0.917kj/kgK

 

Therefore,

W = P(V₂ – V₁) = 3 × 10² (0.0319 – 0.0114)

W = 6.15 KJ/6150J

3⋅10⁵ (0.01) = m/32 (8.31) (290)

m = 39.8165g/ 0.039Kg

n = 39.8165g/32

n = 1.2443 mol

Q = m Cp ∆T

Q = 0.039 × 0.917 × (870 – 290.15)

Q = 20. 74KJ/ 20740J

 

3.10⁵ (0.03) = m/32 (8.31) T₂

T₂ = 870k