The percentage composition of elements in a compound is calculated from the molecular formula of the compound. The molecular mass of a compound is calculated from the atomic masses of the various elements present in the compound. The percentage of mass of each element is then calculated with the help of the following relation. Percentage mass of the element in the compound.
`("Mass of the element")/("Mass of the compound")`
What is the percentage of calcium in calcium carbonate?

Options

A. `32.65`
B. 40
C. `88.9`
D. 18

Explanation

To find the percentage of calcium in calcium carbonate (CaCO₃), we will follow these steps:

### Step 1: Identify the molecular formula of calcium carbonate.
Calcium carbonate consists of calcium (Ca), carbon (C), and oxygen (O). The molecular formula is CaCO₃.

### Step 2: Determine the atomic masses of the elements in calcium carbonate.
- Atomic mass of Calcium (Ca) = 40 g/mol
- Atomic mass of Carbon (C) = 12 g/mol
- Atomic mass of Oxygen (O) = 16 g/mol

### Step 3: Calculate the molecular mass of calcium carbonate (CaCO₃).
The molecular mass of CaCO₃ can be calculated as follows:
- Molecular mass of CaCO₃ = (1 × Atomic mass of Ca) + (1 × Atomic mass of C) + (3 × Atomic mass of O)
- Molecular mass of CaCO₃ = (1 × 40) + (1 × 12) + (3 × 16)
- Molecular mass of CaCO₃ = 40 + 12 + 48
- Molecular mass of CaCO₃ = 100 g/mol

### Step 4: Calculate the percentage mass of calcium in calcium carbonate.
Using the formula for percentage mass:
\[ \text{Percentage mass of Calcium} = \left( \frac{\text{Mass of Calcium}}{\text{Mass of Compound}} \right) \times 100 \]
Substituting the values:
\[ \text{Percentage mass of Calcium} = \left( \frac{40 \text{ g}}{100 \text{ g}} \right) \times 100 \]
\[ \text{Percentage mass of Calcium} = 40\% \]

### Final Answer:
The percentage of calcium in calcium carbonate is **40%**.

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