We give 90 J as heat to a diatomic gas, which then expands at constant pressure. The gas molecules rotate but do not oscillate. By how much does the internal energy of the gas increase?

Explanation

To find the increase in internal energy of the diatomic gas when 90 J of heat is added at constant pressure, we can follow these steps:

### Step 1: Understand the relationship between heat added and internal energy
At constant pressure, the heat added to the system (Q) can be expressed as:
\[ Q = n C_p \Delta T \]
where:
- \( Q \) is the heat added (90 J),
- \( n \) is the number of moles of gas,
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