5moles of an ideal gas (cp = 3r, cv 2r ) are heated from 25°c to 300°c. calculate (a) the change in internal energy of the gas (b) the change in enthalpy of the gas.

Answer :

(a) The change in internal energy of the gas is 22.86 kJ.

(b) The change in enthalpy of the gas is 34.29 kJ.

Explanation :

(a) The formula used for change in internal energy of the gas is:

where,

= change in internal energy = ?

n = number of moles of gas = 5 moles

= heat capacity at constant volume = 2R

R = gas constant = 8.314 J/mole.K

= initial temperature =

= final temperature =

Now put all the given values in the above formula, we get:

The change in internal energy of the gas is 22.86 kJ.

(b) The formula used for change in enthalpy of the gas is:

where,

= change in enthalpy = ?

n = number of moles of gas = 5 moles

= heat capacity at constant pressure = 3R

R = gas constant = 8.314 J/mole.K

= initial temperature =

= final temperature =

Now put all the given values in the above formula, we get:

The change in enthalpy of the gas is 34.29 kJ.