87cm^3 of moist nitrogen is measured at `9^@C` and 659 mm Hg pressure. Find the volume of dry nitrogen at S.T.P. The vapour pressure of water at `9^@C` is 9 mm Hg.

Explanation

To find the volume of dry nitrogen at standard temperature and pressure (STP) from the given conditions of moist nitrogen, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Volume of moist nitrogen (V1) = 87 cm³
- Temperature (T1) = 9°C
- Pressure of moist nitrogen (P1) = 659 mm Hg
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