Question

Calculate the percentage by mass of each of the element in the following compounds.
a) CClF3
b) Ca3(PO4)2

Answer 1

To calculate the percentage by mass of each element in the given compounds, we first need to determine the molar mass of the compounds and then the mass contribution of each element.

### a) CClF3 (Carbon Tetrachloride)

1. **Calculate the Molar Mass**:
- Carbon (C): 12.01 g/mol
- Chlorine (Cl): 35.45 g/mol (3 chlorine atoms)
- Fluorine (F): 19.00 g/mol (3 fluorine atoms)

Molar mass of CClF3 = \[ 1 \times (12.01) + 1 \times (35.45) + 3 \times (19.00) \]
= 12.01 + 35.45 + 57.00
= 104.46 g/mol

2. **Calculate the Mass Percentage**:
- Carbon:
\[
\text{Percentage of C} = \left( \frac{12.01}{104.46} \right) \times 100 \approx 11.49\%
\]

- Chlorine:
\[
\text{Percentage of Cl} = \left( \frac{35.45}{104.46} \right) \times 100 \approx 33.92\%
\]

- Fluorine:
\[
\text{Percentage of F} = \left( \frac{57.00}{104.46} \right) \times 100 \approx 54.59\%
\]

### Summary for CClF3:
- C: 11.49%
- Cl: 33.92%
- F: 54.59%

---

### b) Ca3(PO4)2 (Calcium Phosphate)

1. **Calculate the Molar Mass**:
- Calcium (Ca): 40.08 g/mol (3 calcium atoms)
- Phosphorus (P): 30.97 g/mol (2 phosphorus atoms)
- Oxygen (O): 16.00 g/mol (8 oxygen atoms)

Molar mass of Ca3(PO4)2 = \[ 3 \times (40.08) + 2 \times (30.97) + 8 \times (16.00) \]
= 120.24 + 61.94 + 128.00
= 310.18 g/mol

2. **Calculate the Mass Percentage**:
- Calcium:
\[
\text{Percentage of Ca} = \left( \frac{120.24}{310.18} \right) \times 100 \approx 38.75\%
\]

- Phosphorus:
\[
\text{Percentage of P} = \left( \frac{61.94}{310.18} \right) \times 100 \approx 19.98\%
\]

- Oxygen:
\[
\text{Percentage of O} = \left( \frac{128.00}{310.18} \right) \times 100 \approx 41.27\%
\]

### Summary for Ca3(PO4)2:
- Ca: 38.75%
- P: 19.98%
- O: 41.27%

These calculations yield the percentage by mass of each element in the given compounds.