Q.

Two closed vessels of same volume are joined through a narrow tube and both vessels are filled with air of pressure 90 kPa and temperature 400 K. Keeping the temperature of one vessel constant at 400 K, the second vessel temperature is raised to 500 K. The final pressure in the vessels is ______ kPa.               [2026]

1 100  
2 120  
3 90  
4 105  

Ans.

(1)

Using mole conservation: ntotal=n1+n2

PfVTf+PfVTf=PiVTi+PiVTi

PfV(1400+1500)=2PiVTi

Pf×V×900400×500=2×90×103×V400

Pf=180×103×59=180×103 Pa=100 kPa