4. A 1 m3 rigid tank has propane at 100 kPa, 300 K and connected by a valve to another tank of 0.5 M3 with propane at 250 kPa, 400 K. The valve is opened and the two tanks come to a uniform state at 325 K. What is the final pressure?

139.97 kPa

Explanation:

Assuming propane is an ideal gas

PV = nRT

n₁ ( number of mole f the first gas) of the 1 m³ rigid tank = P₁V₁ / RT₁ R gas constant = 8.314 J/mol

n₁ = 100kPa × 1 m³ / (8.314 J/mol × 300 K) = 0.0401 mol

n₂ = 0.5 m³ × 250 kPa / ( 8.314J/mol × 400 K) = 0.0376 mol where n₂ is the number of mole of the second gas

n total = n₁ + n₂ = 0.0401 mol + 0.0376 mol = 0.0777 mol

PV = nRT

P final pressure = nRT  / V where V = V₁ + V₂ = 1 m³ + 0.5 m³ = 1.5 m³

P final pressure = 0.0777 mol × 8.314 J/mol × 325 K / 1.5 m³ = 139.97 kPa