Mass of `112 cm^(3)` of `NH_(3)` gas at S.T.P. is

Options

A. `0.085 g`
B. `0.850 g`
C. `8.5 g`
D. `80.5 g`

Explanation

To find the mass of 112 cm³ of NH₃ gas at standard temperature and pressure (S.T.P.), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Volume at STP**:
At standard temperature and pressure (S.T.P.), 1 mole of any ideal gas occupies 22,400 mL (or cm³).

2. **Calculate Moles of NH₃**:
We need to calculate the number of moles of NH₃ in 112 cm³.
\[ \text{Moles of NH₃} = \frac{\text{Volume of NH₃}}{\text{Volume of 1 mole at STP}} = \frac{112 \, \text{cm}^3}{22400 \, \text{cm}^3} \]

3. **Perform the Calculation**:
\[ \text{Moles of NH₃} = \frac{112}{22400} = 0.005 \, \text{moles} \]

4. **Find the Molar Mass of NH₃**:
The molar mass of ammonia (NH₃) is calculated as follows:
- Nitrogen (N) = 14 g/mol
- Hydrogen (H) = 1 g/mol (and there are 3 H atoms)
\[ \text{Molar mass of NH₃} = 14 + (3 \times 1) = 17 \, \text{g/mol} \]

5. **Calculate the Mass of NH₃**:
Now, we can calculate the mass using the formula:
\[ \text{Mass} = \text{Moles} \times \text{Molar Mass} = 0.005 \, \text{moles} \times 17 \, \text{g/mol} \]

6. **Perform the Final Calculation**:
\[ \text{Mass} = 0.085 \, \text{grams} \]

### Final Answer:
The mass of 112 cm³ of NH₃ gas at S.T.P. is **0.085 grams**.

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