Chlorophyll, the green colouring matter of plants responsible for photosynthesis, contains `2.68%` of magnesium by mass. Calculate the number of magnesium atoms in `2.00 g` of chlorophyll.

Options

A. `1.345xx10^(21)`
B. `1.345xx10^(20)`
C. `13.45xx10^(21)`
D. `1.345xx10^(23)`

Explanation

To solve the problem of calculating the number of magnesium atoms in 2.00 g of chlorophyll, we can follow these steps:

### Step 1: Identify the mass of chlorophyll and the mass percentage of magnesium
- Given:
- Mass of chlorophyll = 2.00 g
- Mass percentage of magnesium = 2.68%

### Step 2: Calculate the mass of magnesium in 2.00 g of chlorophyll
- We can use the formula for mass percentage:
\[ \text{Mass of magnesium} = \left( \frac{\text{Mass percentage of magnesium}}{100} \right) \times \text{Mass of chlorophyll} \]
- Substituting the values:
\[ \text{Mass of magnesium} = \left( \frac{2.68}{100} \right) \times 2.00 = 0.0536 \text{ g} \]

### Step 3: Find the molar mass of magnesium
- The molar mass of magnesium (Mg) is approximately 24 g/mol.

### Step 4: Calculate the number of moles of magnesium in 0.0536 g
- Using the formula:
\[ \text{Number of moles} = \frac{\text{Mass of magnesium}}{\text{Molar mass of magnesium}} \]
- Substituting the values:
\[ \text{Number of moles} = \frac{0.0536 \text{ g}}{24 \text{ g/mol}} \approx 0.002233 \text{ mol} \]

### Step 5: Calculate the number of magnesium atoms
- Using Avogadro's number (approximately \(6.022 \times 10^{23}\) atoms/mol):
\[ \text{Number of atoms} = \text{Number of moles} \times \text{Avogadro's number} \]
- Substituting the values:
\[ \text{Number of atoms} = 0.002233 \text{ mol} \times 6.022 \times 10^{23} \text{ atoms/mol} \approx 1.344 \times 10^{21} \text{ atoms} \]

### Final Answer
The number of magnesium atoms in 2.00 g of chlorophyll is approximately \(1.34 \times 10^{21}\) atoms.

---