Select the correct statement. In the gas equation, `PV=nRT`

Options

A. n is the number of molecules of a gas
B. n moles of the gas have a volume V
C. V denotes volume of one mole of the gas
D. P is the pressure of the gas when only one mole of gas is present.

Answer

To solve the question regarding the ideal gas equation \( PV = nRT \), we need to analyze the components of the equation and the statements provided.

### Step-by-Step Solution:

1. **Understanding the Ideal Gas Equation**:
The ideal gas equation is given by:
\[ PV = nRT \]
where:
- \( P \) = Pressure of the gas
- \( V \) = Volume of the gas
- \( n \) = Number of moles of the gas
- \( R \) = Ideal gas constant
- \( T \) = Temperature of the gas in Kelvin

2. **Analyzing the Statements**:
We need to evaluate each statement provided in the question to determine which one is correct.

**Statement A**: "n is the number of molecules of gas."
- This statement is incorrect because \( n \) represents the number of moles, not the number of molecules. The number of molecules can be calculated using Avogadro's number.

**Statement B**: "n moles of gas have volume V at constant pressure and temperature."
- This statement is correct. The equation \( PV = nRT \) applies under the condition of constant temperature and pressure for \( n \) moles of gas occupying volume \( V \).

**Statement C**: "V denotes the volume of one mole of gas at constant pressure and temperature."
- This statement is incorrect. \( V \) represents the volume of \( n \) moles of gas, not just one mole.

**Statement D**: "P is the pressure of gas when only one mole of gas is present at constant volume and temperature."
- This statement is also incorrect. \( P \) represents the pressure of \( n \) moles of gas in volume \( V \), not just one mole.

3. **Conclusion**:
After evaluating all the statements, the correct statement is:
- **Statement B**: "n moles of gas have volume V at constant pressure and temperature."

### Final Answer:
The correct statement is **B**: "n moles of gas have volume V at constant pressure and temperature."

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