According to Bohr's theory, the angular momentum of electron in the fifth Bohr orbit is:

Options

A. `25 h/pi`
B. `1.0 h/pi`
C. `10 h/pi`
D. `2.5 h/pi`

Explanation

To find the angular momentum of an electron in the fifth Bohr orbit according to Bohr's theory, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Formula for Angular Momentum**:
According to Bohr's theory, the angular momentum \( L \) of an electron in a Bohr orbit is given by the formula:
\[ L = n \frac{h}{2\pi} \]
where:
- \( L \) = angular momentum
- \( n \) = principal quantum number (the orbit number)
- \( h \) = Planck's constant
- \( \pi \) = constant (approximately 3.14)

2. **Identify the Principal Quantum Number**:
For the fifth Bohr orbit, the principal quantum number \( n \) is 5.

3. **Substitute the Value of \( n \) into the Formula**:
Substitute \( n = 5 \) into the angular momentum formula:
\[ L = 5 \frac{h}{2\pi} \]

4. **Simplify the Expression**:
This can be simplified to:
\[ L = \frac{5h}{2\pi} \]

5. **Final Result**:
Thus, the angular momentum of the electron in the fifth Bohr orbit is:
\[ L = \frac{5h}{2\pi} \]

### Conclusion:
The correct answer for the angular momentum of the electron in the fifth Bohr orbit is \( \frac{5h}{2\pi} \).