Certain volume of a gas exerts on its walls some pressure at a particular temperature . It has been found that by reducing the volume of the gas to half of its original value the pressure become twice that of the initial value at constant temperature . this happens because

Options

A. mass of the gas increases with pressure
B. speed of the gas molecules decreases
C. more number of gas molecules strike the surface per second
D. gas molecules attract each other .

Answer

To solve the question, let's analyze the situation step by step.

### Step 1: Understand the Initial Conditions
We have a certain volume of gas that exerts a specific pressure at a given temperature. This is our starting point.

**Hint:** Remember that pressure, volume, and temperature are related in gases according to the gas laws.

### Step 2: Identify the Change in Volume
The problem states that the volume of the gas is reduced to half of its original value. This means if the original volume is V, the new volume is V/2.

**Hint:** Think about how reducing the volume of a gas affects the space available for gas molecules to move.

### Step 3: Analyze the Effect on Pressure
According to the problem, when the volume is halved, the pressure becomes twice the initial pressure. This means if the original pressure is P, the new pressure is 2P.

**Hint:** Recall the relationship between pressure and volume as described by Boyle's Law, which states that pressure is inversely proportional to volume when temperature is constant.

### Step 4: Consider the Reason for Increased Pressure
When the volume is decreased, the gas molecules have less space to move around. As a result, more gas molecules collide with the walls of the container per unit time, leading to an increase in pressure.

**Hint:** Visualize gas molecules moving in a smaller space; they will hit the walls more frequently.

### Step 5: Evaluate the Options Given
1. **Mass of the gas increases with pressure:** This is incorrect; mass remains constant.
2. **Speed of the gas molecules decreases:** This is also incorrect; the speed does not decrease due to volume reduction.
3. **More number of gas molecules strike the surface per second:** This is correct; with reduced volume, collisions increase, leading to higher pressure.
4. **Gas molecules attract each other:** This is incorrect; gas molecules do not attract each other significantly under normal conditions.

### Conclusion
The correct answer is that the increase in pressure occurs because more gas molecules strike the surface per second when the volume is halved.

**Final Answer:** The correct reason is that more number of gas molecules strike the surface per second, leading to an increase in pressure.

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