Question

The specific heat of air at constant volume is 0.172 Cal $g^{-1}$$C^{-1}$. The change in internal energy when 5g of air is heated from 0C to 4C at constant volume is:

• A. 28.8 J
• B. 14.4 J
• C. 7.2 J
• D. 3.51 J

Answer 1

Answer: (B)

14.4 J

Given: Specific heat of air = 0172 Cal/gC

Mass of air= 5g

Initial temperature= 0C

Final temperature = 4C

Solution: At constant volume the change in internal energy is given by,

$△U=m{C}_p△T$

As, $△T=4-0=4C$

Substituting the values we get,

$△U=3.44Cal$

Also, $1Cal=4.2J$

$\therefore △U=4.2J\times 3.44=14.188J\sim 14.4J$

Hence, the correct option is (B).