Question

2.5 KG of a gas heated from 80°c to 250°c according to constant pressure process.If specific heats are cp=1.005KJ/cal, cv=0.714kg/cal find. 1Heat required 2.change in internal energy 3. work done on the gas​

Answer 1

2.5 kg of a gas heated from 80°C to 250°C according to constant pressure process. If specific heats are Cp = 1.005Kcal/kg/°C , Cv = 0.71 Kcal/kg/°C

We have to find

1. heat required
2. change in internal energy
3. work done on the gas

1. heat required = change in energy at constant pressure

= mCp∆T

= 2.5 kg × 1.005Kcal/Kg/°C × (250 - 80)°C

= 2.5 × 1.005 × 170 Kcal

= 427.125 Kcal

Therefore the heat required is 427.125 Kcal

2. internal energy change = change in energy at constant volume

= mCv∆T

= 2.5 kg × 0.714 Kcal/Kg/°C × (250 - 80)°C

= 2.5 × 0.714 × 170

= 303.45 Kcal

Therefore the change in internal energy is 303.45 Kcal

3. work done on the gas = Q - U

[ from 1st law of thermodynamics]

= (427.125 - 303.45) KCal

= 124.325 Kcal

Therefore work done on the gas is 124.325KCal