Question

Find the change in internal energy of the system when a system absorbs 2 kilocalorie of heat and at the same time does 500 joule of work

• A. 7900 J
• B. 8200 J
• C. 5600 J
• D. 6400 J

Answer 1

Answer: (A)

7900 J

Answer 2

$\Delta Q = 2kcal = 2 \times 10^{3} \times 4.2J = 8400J$and $\Delta W = 500J.$

Hence from $\Delta Q = \Delta U + \Delta W,$ $\Delta W = \Delta Q - \Delta U$ = 8400 – 500

= 7900 J