The mass of `1/12`th of `""^12C` is same as that of

Options

A. `1/28` of `N_(2)`
B. 1 u
C. `1/8 th` of O
D. `1/12`th of He

Answer

To solve the question, we need to determine what the mass of `1/12` of `C-12` (Carbon-12) is equivalent to in terms of other substances.

### Step-by-step Solution:

1. **Understand the Mass of Carbon-12**:
The atomic mass of Carbon-12 is defined as 12 atomic mass units (u).

2. **Calculate `1/12` of Carbon-12**:
To find `1/12` of the mass of Carbon-12:
\[ \text{Mass of } \frac{1}{12} \text{ of } C-12 = \frac{1}{12} \times 12 \, \text{u} = 1 \, \text{u} \]

3. **Identify Equivalent Masses**:
Now, we need to find which of the given options also has a mass of `1 u`.

- **Option 1**: `1/28` of `N2` (Nitrogen gas)
- The molecular weight of `N2` is \( 2 \times 14 \, \text{u} = 28 \, \text{u} \).
- Therefore, \( \frac{1}{28} \times 28 \, \text{u} = 1 \, \text{u} \).

- **Option 2**: `1/28` of `N2` (same as above, hence also correct).

- **Option 3**: `1/8` of `O2` (Oxygen gas)
- The molecular weight of `O2` is \( 2 \times 16 \, \text{u} = 32 \, \text{u} \).
- Therefore, \( \frac{1}{8} \times 32 \, \text{u} = 4 \, \text{u} \) (not equal to `1 u`).

- **Option 4**: `1/12` of `He` (Helium)
- The atomic weight of Helium is \( 4 \, \text{u} \).
- Therefore, \( \frac{1}{12} \times 4 \, \text{u} = \frac{4}{12} \, \text{u} = \frac{1}{3} \, \text{u} \) (not equal to `1 u`).

4. **Conclusion**:
The correct options that have the same mass as `1/12` of `C-12` are:
- Option 1: `1/28` of `N2`
- Option 2: `1/28` of `N2` (repeated, hence still correct)

### Final Answer:
The mass of `1/12` of `C-12` is the same as that of `1/28` of `N2`.