Calculate the number of atoms present in 7.1 g of chlorine ?

Options

A. `0.2 N_(A)`
B. `0.3N_(A)`
C. `0.4N_(A)`
D. `0.5 N_(A)`

Answer

To calculate the number of atoms present in 7.1 g of chlorine, we can follow these steps:

### Step 1: Determine the molar mass of chlorine
Chlorine (Cl) has a molar mass of approximately 35.5 g/mol. For simplicity, we can round it to 35 g/mol for our calculations.

### Step 2: Calculate the number of moles of chlorine
To find the number of moles (n) of chlorine in 7.1 g, we use the formula:
\[ n = \frac{\text{mass}}{\text{molar mass}} \]
Substituting the values:
\[ n = \frac{7.1 \, \text{g}}{35 \, \text{g/mol}} \approx 0.2 \, \text{moles} \]

### Step 3: Use Avogadro's number to find the number of atoms
Avogadro's number (N_A) is approximately \(6.022 \times 10^{23}\) atoms/mol. The number of atoms in 0.2 moles of chlorine can be calculated as:
\[ \text{Number of atoms} = n \times N_A \]
Substituting the values:
\[ \text{Number of atoms} = 0.2 \, \text{moles} \times 6.022 \times 10^{23} \, \text{atoms/mol} \approx 1.2044 \times 10^{23} \, \text{atoms} \]

### Final Answer
The number of atoms present in 7.1 g of chlorine is approximately \(1.2044 \times 10^{23}\) atoms.

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