The relationship which describes the variation of vapour pressure with temperature is called

Options

A. Hess's law
B. Arrhenius equation
C. Kirchoff's law
D. Clausis-Clapeyron equation

Explanation

To solve the question regarding the relationship that describes the variation of vapor pressure with temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the specific relationship that describes how vapor pressure changes with temperature.

2. **Identifying the Options**: The options given are:
- a) Hash law
- b) Arrhenius equation
- c) Krzysztof law
- d) Klesz-Clapeyron equation

3. **Evaluating Each Option**:
- **Hash Law**: This law is related to the calculation of total heat of formation and does not describe vapor pressure.
- **Arrhenius Equation**: This equation relates to the rate constant of a reaction and its dependence on temperature, not specifically vapor pressure.
- **Krzysztof Law**: This law pertains to resistance and is not related to vapor pressure.
- **Klesz-Clapeyron Equation**: This equation specifically describes the relationship between vapor pressure and temperature, making it a strong candidate.

4. **Recalling the Klesz-Clapeyron Equation**: The Klesz-Clapeyron equation is given by:
\[ \ln \frac{P_1}{P_2} = \frac{\Delta H_{vap}}{R} \left( \frac{1}{T_2} - \frac{1}{T_1} \right) \]
Here, \(P\) represents vapor pressure, \(\Delta H_{vap}\) is the enthalpy of vaporization, \(R\) is the gas constant, and \(T\) is the temperature.

5. **Conclusion**: Given the analysis of the options, the correct answer is:
- **Klesz-Clapeyron equation**.

### Final Answer:
The relationship which describes the variation of vapor pressure with temperature is called the **Klesz-Clapeyron equation**.