Le Chatelier's Principle
If a system at equilibrium is subjected to a change of any one of the factors such as concentration, pressure or temperature, the system adjusts itself in such a way as to nullify the effect of that change.
Change of pressure : If a system consists of gases, then the concentration of all the components can be alterd by changing the pressure. To increase the pressure on the system,the volume has to be decreased proportionally. The total number of mols per unit volume will now be more and the equilibrium will shift in the direction in which there is a decrease in number of moles i,e. towards the direction in which there can be decrease in pressure.
Effect of pressure on melting point : There are two types of solids:
(a) Solids whose volume decreases on melting e.g., ice,diamond carborundum magnesium nitride and quratz.
Solids (higher volume)`hArr`Liquid (lower volume) The process of melting is facilitated at high pressure, thus, melting point is lowerd.
(b) Solids whose volume increase on melting e.g.,Fe,Cu,Ag,Au,etc.
Solid (lower volume)`hArr` Liquid (higher volume) In this case the process of melting become difficult at high pressure, thus melting point becomes high.
(c) Solubility of substances : When solid substances are dissolved in water, either heat is evolved (exothermic) or heat is absorbed (endothermic).
`KCI+aqhArrKCI(aq)-heat`
In such cases, solubility increase with increase in temperature. Consider the case of KOH, when this is dissolved,heat is evolved.
`KOH+aqhArrKOH(aq)+heat`
In such cases, solubility decrease with increase in temperature.
(d) Solubility of gases in liquids : When a gas dissolves in liquid,there is decrease in volume. Thus increase of pressure will favour the dissolution of gas in liquid.
A gas 'X' when dissolved in water,heat is evolved. Then solubility of 'X' will increase:

Options

A. Low pressure, high temperature
B. Low pressure, low temperature
C. high pressure, high temperature
D. high pressure, low temperature

Explanation

### Step-by-Step Solution:

1. **Understanding the Situation**: We are given that a gas X, when dissolved in water, evolves heat. This indicates that the dissolution of gas X is an exothermic process. In thermodynamic terms, this means that the enthalpy change (ΔH) for the dissolution is negative.

2. **Applying Henry's Law**: According to Henry's law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. Therefore, if we increase the pressure, the solubility of gas X will also increase.

3. **Considering Temperature Effects**: Since the dissolution of gas X is exothermic, we can apply Le Chatelier's Principle. This principle states that if a system at equilibrium is subjected to a change in conditions (like temperature), the system will adjust itself to counteract that change. For exothermic reactions:
- Increasing the temperature shifts the equilibrium to the left (favoring the reactants).
- Decreasing the temperature shifts the equilibrium to the right (favoring the products).

4. **Determining the Conditions for Increased Solubility**: To increase the solubility of gas X:
- We need to apply high pressure (to favor the dissolution of gas, according to Henry's law).
- We also need to decrease the temperature (to shift the equilibrium towards the products, which in this case is the dissolved gas).

5. **Conclusion**: Therefore, the conditions required to increase the solubility of gas X in water are high pressure and low temperature.

### Final Answer:
The correct option is high pressure and low temperature.

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