The number of molecules in 4.25 g of ammonia is approximately

Options

A. `1xx10^(23)`
B. `1.5xx10^(23)`
C. `2.0xx10^(23)`
D. `2.5xx10^(23)`

Explanation

To find the number of molecules in 4.25 g of ammonia (NH₃), we can follow these steps:

### Step 1: Determine the molar mass of ammonia (NH₃)
The molar mass of ammonia can be calculated using the atomic masses of nitrogen (N) and hydrogen (H):
- Atomic mass of nitrogen (N) = 14 g/mol
- Atomic mass of hydrogen (H) = 1 g/mol

Since ammonia has one nitrogen atom and three hydrogen atoms, the molar mass is:
\[ \text{Molar mass of NH}_3 = 14 \, \text{g/mol} + (3 \times 1 \, \text{g/mol}) = 14 + 3 = 17 \, \text{g/mol} \]

### Step 2: Calculate the number of moles in 4.25 g of ammonia
To find the number of moles, we use the formula:
\[ \text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]
Substituting the values:
\[ \text{Number of moles} = \frac{4.25 \, \text{g}}{17 \, \text{g/mol}} \]
Calculating this gives:
\[ \text{Number of moles} \approx 0.250 \, \text{moles} \]

### Step 3: Convert moles to molecules
Using Avogadro's number, which is \( 6.022 \times 10^{23} \) molecules/mol, we can find the number of molecules:
\[ \text{Number of molecules} = \text{Number of moles} \times \text{Avogadro's number} \]
Substituting the values:
\[ \text{Number of molecules} = 0.250 \, \text{moles} \times 6.022 \times 10^{23} \, \text{molecules/mol} \]
Calculating this gives:
\[ \text{Number of molecules} \approx 1.505 \times 10^{23} \, \text{molecules} \]

### Final Answer
The number of molecules in 4.25 g of ammonia is approximately \( 1.505 \times 10^{23} \) molecules.

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