Under which of the following conditions applied together, a gas deviates most from the ideal behaviour ?

Options

A. Low pressure
B. High pressure
C. Low temperature
D. High temperature

Explanation

To determine under which conditions a gas deviates most from ideal behavior, we need to analyze the relationship between pressure, temperature, and the behavior of gases.

### Step-by-Step Solution:

1. **Understanding Ideal Gas Behavior**:
- An ideal gas follows the ideal gas equation: \( PV = nRT \), where \( P \) is pressure, \( V \) is volume, \( n \) is the number of moles of gas, \( R \) is the ideal gas constant, and \( T \) is temperature.
- Ideal gases are theoretical and do not exist in reality. Real gases behave ideally under certain conditions.

2. **Conditions for Ideal Behavior**:
- Gases behave more ideally at **low pressure** and **high temperature**. Under these conditions, the intermolecular forces are negligible, and the volume occupied by the gas molecules themselves is small compared to the volume of the container.

3. **Conditions for Non-Ideal Behavior**:
- Real gases deviate from ideal behavior at **high pressure** and **low temperature**.
- At high pressures, gas molecules are forced closer together, leading to significant intermolecular forces and a larger volume than predicted by the ideal gas law.
- At low temperatures, the kinetic energy of gas molecules decreases, allowing intermolecular forces to have a more pronounced effect, leading to deviations from ideal behavior.

4. **Identifying the Correct Conditions**:
- Therefore, the conditions under which a gas deviates most from ideal behavior are:
- **High pressure** (Option B)
- **Low temperature** (Option C)

### Conclusion:
The gas deviates most from ideal behavior under the conditions of **high pressure and low temperature**.

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