A gas expands by 2 litres against a constant pressure of 2 atm. Calculate work done in Joule and Calorie.

Explanation

To solve the problem of calculating the work done by a gas expanding against a constant pressure, we can follow these steps:

### Step 1: Understand the formula for work done
The work done (W) by a gas during expansion at constant pressure can be calculated using the formula:
\[ W = -P \Delta V \]
where:
- \( P \) = pressure (in atm)
- \( \Delta V \) = change in volume (in liters)
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