Select the correct statements(s):

Options

A. At Boyle's temperature a real gas behaves like an ideal gas at low pressure
B. Above critical conditions, a real behave like an ideal gas
C. For hydrogen gas 'b' dominates over 'a' all at temperature
D. At high pressure van der Waals' constatn 'b' dominated over 'a'

Answer

To solve the question, we need to analyze each statement regarding the behavior of real gases compared to ideal gases. Let's go through each option step by step.

### Step 1: Analyze Option A
**Statement:** At Boyle's temperature, a real gas behaves like an ideal gas at low pressure.

**Explanation:** Boyle's temperature (TB) is defined as the temperature at which a real gas behaves ideally at low pressures. This statement is correct because at Boyle's temperature, the intermolecular forces are minimized, allowing the gas to follow the ideal gas law more closely.

### Step 2: Analyze Option B
**Statement:** Above critical conditions, a real gas behaves like an ideal gas.

**Explanation:** Above the critical temperature and pressure, gases cannot be liquefied by pressure alone, and they behave more ideally. However, this statement is somewhat misleading because while gases may behave more ideally, they do not behave perfectly like ideal gases. Therefore, this statement is also considered correct in the context of the question.

### Step 3: Analyze Option C
**Statement:** For hydrogen gas, B dominates over A at temperature.

**Explanation:** In the van der Waals equation, 'a' accounts for the attractive forces between molecules, while 'b' accounts for the volume occupied by the molecules. For hydrogen (and helium), the attractive forces (represented by 'a') dominate over the volume effects (represented by 'b'). Thus, this statement is incorrect.

### Step 4: Analyze Option D
**Statement:** At high pressure, van der Waals constant B dominates over A.

**Explanation:** At high pressures, the volume occupied by the gas molecules becomes significant, and the repulsive forces (related to constant 'b') dominate over the attractive forces (related to constant 'a'). Therefore, this statement is correct.

### Conclusion
Based on the analysis:
- **Correct Statements:** A, B, and D
- **Incorrect Statement:** C

The correct answer is A, B, and D.

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