A: Number of atoms in 2 mole of `NH_(3)` is equal to number of atoms in 4 mole of `CH_(4)`
R: Both are chemically similar species.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion
C. If Assertion is true statement but Reason is false
D. If both Assertion and Reason are false statements

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the number of atoms in 2 moles of \( NH_3 \) is equal to the number of atoms in 4 moles of \( CH_4 \).
- We need to calculate the total number of atoms in each case.

2. **Calculating Atoms in \( NH_3 \)**:
- One mole of \( NH_3 \) contains 4 atoms (1 nitrogen and 3 hydrogen).
- Therefore, 2 moles of \( NH_3 \) will contain:
\[ \text{Total atoms in } 2 \text{ moles of } NH_3 = 2 \text{ moles} \times 4 \text{ atoms/mole} = 8 \text{ atoms} \]
- Since we are using Avogadro's number \( N_a \) (approximately \( 6.022 \times 10^{23} \)), the total number of atoms is:
\[ 8 \times N_a \]

3. **Calculating Atoms in \( CH_4 \)**:
- One mole of \( CH_4 \) contains 5 atoms (1 carbon and 4 hydrogen).
- Therefore, 4 moles of \( CH_4 \) will contain:
\[ \text{Total atoms in } 4 \text{ moles of } CH_4 = 4 \text{ moles} \times 5 \text{ atoms/mole} = 20 \text{ atoms} \]
- Again, using Avogadro's number \( N_a \), the total number of atoms is:
\[ 20 \times N_a \]

4. **Comparing the Two Results**:
- From the calculations:
- Atoms in 2 moles of \( NH_3 = 8 \times N_a \)
- Atoms in 4 moles of \( CH_4 = 20 \times N_a \)
- Clearly, \( 8 \times N_a \) is not equal to \( 20 \times N_a \). Therefore, the assertion is **false**.

5. **Understanding the Reason**:
- The reason states that both \( NH_3 \) and \( CH_4 \) are chemically similar species.
- However, \( NH_3 \) (ammonia) contains nitrogen and hydrogen, while \( CH_4 \) (methane) contains carbon and hydrogen. They have different chemical properties and structures.
- Thus, the reason is also **false**.

6. **Conclusion**:
- Since both the assertion and the reason are false, the correct answer is option D: Both assertion and reason are false.