The first law thermodynamics was gives as `q=Delta U+(-w)`, where q is heat given to a system and `Delta U` represent increase in internal energy and -w is work done by the system. Various process such as isothermal, adiabatic, cyclic, isobaric and isochoric process in terms to first law of thermodynamics leads for important results. The molar heat capacity for 1 mole of monoatomic gas is 3/2R at constant volume and 5/2R at constant pressure.
A system is allowed to move from state A to B following path ACB by absorbing 80 J of heat energy. The work done by the system is 30 J. The work done by the system in reaching state B from A is 10 J through path ADB which statements are correct :

1. Increase in internal energy from state A to state B is 50 J.
2. If path ADB is followed to reach state B. `Delta U = 50J`
3. If work done by the system in path AB is 20 J, the heat absorbed during path AB = 70 J.
4. The value `U_(C)-U_(A)` is equal to `U_(D)-U_(B)`.
5. Heat absorbed by the system to reach B from A through path ADB is 60 J.

Options

A. 1, 5
B. 1, 3,5
C. 1, 2,3,5
D. 1, 4,5

Answer

C

Explanation

`ACB = AC+BC, ADB = AD + BD` Heat absorbed 80J. Work done by the system `= 10 J :. w = -10 J :. w = -30` Also `w = - 10J :. UB-UA = 50J :. q = 50+10 = 60J`