A manometer is connected to gas container. Then the mercury level rises by 2 cm in the arm of the manometer which is not connected to the container.
If the atmospheric pressure is 76 cm of mercury, then the pressure of the gas is ________ cm of mercury.

Options

A. 80
B. 76
C. 72
D. 78

Explanation

To solve the problem, we need to determine the pressure of the gas in the container using the information provided about the manometer and the atmospheric pressure.

### Step-by-Step Solution:

1. **Understand the Manometer Setup:**
A manometer is a device used to measure the pressure of a gas by comparing it to the atmospheric pressure. It typically consists of a U-shaped tube filled with a liquid (in this case, mercury).

2. **Identify the Given Values:**
- Atmospheric pressure (P_atm) = 76 cm of mercury
- Rise in mercury level in the arm not connected to the gas container = 2 cm

3. **Determine the Pressure of the Gas:**
When the mercury level rises by 2 cm in the arm not connected to the gas container, it indicates that the pressure of the gas is greater than the atmospheric pressure. The pressure difference is equal to the height difference of the mercury column.

Therefore, the pressure of the gas (P_gas) can be calculated as:
\[ P_{gas} = P_{atm} + h \]
where \( h \) is the height difference in mercury, which is 2 cm.

4. **Substituting the Values:**
\[ P_{gas} = 76 \, \text{cm} + 2 \, \text{cm} = 78 \, \text{cm of mercury} \]

5. **Final Answer:**
The pressure of the gas is **78 cm of mercury**.