PHYSICS QUESTION 1

Question

8.1 moles of an ideal monatomic gas expand adiabatically, performing 8800  of work in the process.

What is the change in temperature of the gas during this expansion?

Answer 1

Let's review the first law of thermodynamics before answering the question.

The internal energy of a system that spends energy in the form of work (dW), and gains energy (dQ) from outside in the form of heat changes in accordance with the conservation of energy principle.i.e.

dU = dQ - dW

In an adiabatic expansion there is no heat exchange from the outside. So, dQ = 0, and all the work necessary to expand is derived from the internal energy of the system. This lowers the temperature as the system's energy is expended.

dU = -dW

By definition, work performed during expansion of a gas is = P.dV

Using the ideal gas law, we can also write

P.dV = nR.dT

We are given the amount of work performed (the units are missing), P.dV, and the number of moles of gas, n. The gas constant R in MKS units is 8.314 J/mol-K. You can calculate the change in temperature based on the above gas law equation.

Hope this helps.