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: Identify the molar mass of chlorine
The molar mass of chlorine (Cl) is approximately 35 g/mol.

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

### Step 3: Use Avogadro's number to find the number of atoms
Avogadro's number (Na) is approximately \(6.022 \times 10^{23}\) atoms/mol. To find the total number of atoms in 0.2 moles of chlorine, we multiply the number of moles by Avogadro's number:
\[ \text{Number of atoms} = \text{Number of moles} \times \text{Avogadro's number} \]
Substituting the values:
\[ \text{Number of atoms} = 0.2 \text{ moles} \times 6.022 \times 10^{23} \text{ atoms/mole} \approx 1.2044 \times 10^{23} \text{ atoms} \]

### 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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