A certain gas is compressed adiabatically. The amount of work done on the gas is 800 J. What is the change in the internal (thermal) energy of the gas? a. 0 Jb. 800 Jc. - 800 Jd. 400 J

C. - 800J

Explanation:

Q = W + ∆U

Q = quantity of heat transferred = 0 for adiabatic processes, W = work done = 800J

∆U = Q - W = 0 - 800 = - 800J

Answer: b. 800 J

∆U = - W = - (-800J)

∆U = 800J

Explanation:

In an adiabatic process, no heat is added or removed from the system.

Change in the internal energy of a system can be written as;

∆U = Q - W

Where ∆U is the change in the internal energy,

Q is the heat added to the system and W is the workdone by system.

For adiabatic process

∆U = - W (since Q = 0, no heat addition or removal)

Since in the case above.

Workdone on system is 800J

Workdone by system W = - 800J

So,

∆U = - W = - (-800J)

∆U = 800J