The percentage composition of carbon by mole in methane is:

Options

A. `25%`
B. `80%`
C. `75%`
D. `20%`

Explanation

To find the percentage composition of carbon by mole in methane (CH₄), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the molecular formula of methane**:
- Methane is represented as CH₄, which means it contains one carbon (C) atom and four hydrogen (H) atoms.

2. **Determine the number of moles of carbon in one mole of methane**:
- In one mole of methane (CH₄), there is 1 mole of carbon.

3. **Calculate the total number of moles of all atoms in one mole of methane**:
- In one mole of CH₄, there are a total of 5 moles of atoms (1 mole of C + 4 moles of H = 5 moles of atoms).

4. **Use the formula for percentage composition by mole**:
- The formula for percentage composition by mole is:
\[ \text{Percentage composition of C} = \left( \frac{\text{Number of moles of C}}{\text{Total moles of all atoms}} \right) \times 100 \]

5. **Substitute the values into the formula**:
- Number of moles of C = 1
- Total moles of all atoms = 5
- Therefore,
\[ \text{Percentage composition of C} = \left( \frac{1}{5} \right) \times 100 = 20\% \]

6. **Conclusion**:
- The percentage composition of carbon by mole in methane is **20%**.