Q.

Density of water at 4°C and 20°C are 1000 kg/m3 and 998 kg/m3 respectively. The increase in internal energy of 4 kg of water when it is heated from 4°C to 20°C is ________ J.  

(Specific heat capacity of water = 4.2 J/kg, and 1 atmospheric pressure = 105 Pa)                   [2026]

1 315826.2  
2 234699.2  
3 258700.8  
4 268799.2  

Ans.

(4)

Q=msΔT=4×4200×16 J=268800 J

W=PΔV

ΔV=(mρf-mρi)=4[1998-11000]

P=105 Pa

 W=105×4[1998-11000]=8×105103×9980.8 J

ΔU=Q-W=268799.2 J