Question

Calculate the percentage by mass of each of the element in the following compounds.
A. Chloro- trifluoro -CCIF3
B. Calcium phosphate- 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 entire compound and then calculate the contribution of each element to this total molar mass.

### A. Chloro-trifluoro-CCIF3

1. **Determine the molar mass:**
- Carbon (C) = 12.01 g/mol (There are 2 carbons in CClF3)
- Chlorine (Cl) = 35.45 g/mol (There is 1 Cl in CClF3)
- Fluorine (F) = 19.00 g/mol (There are 3 F in CClF3)

The molar mass of CClF3:
\[
M = 2(12.01) + 1(35.45) + 3(19.00)
\]
\[
M = 24.02 + 35.45 + 57.00
\]
\[
M = 116.47 \, \text{g/mol}
\]

2. **Calculate the percentage by mass of each element:**
- %C:
\[
\text{%C} = \left(\frac{24.02}{116.47}\right) \times 100 \approx 20.6\%
\]

- %Cl:
\[
\text{%Cl} = \left(\frac{35.45}{116.47}\right) \times 100 \approx 30.4\%
\]

- %F:
\[
\text{%F} = \left(\frac{57.00}{116.47}\right) \times 100 \approx 49.0\%
\]

**Final results for CClF3:**
- **%C** = 20.6%
- **%Cl** = 30.4%
- **%F** = 49.0%

---

### B. Calcium Phosphate - Ca3(PO4)2

1. **Determine the molar mass:**
- Calcium (Ca) = 40.08 g/mol (There are 3 Ca)
- Phosphorus (P) = 30.97 g/mol (There are 2 P)
- Oxygen (O) = 16.00 g/mol (There are 8 O)

The molar mass of Ca3(PO4)2:
\[
M = 3(40.08) + 2(30.97) + 8(16.00)
\]
\[
M = 120.24 + 61.94 + 128.00
\]
\[
M = 310.18 \, \text{g/mol}
\]

2. **Calculate the percentage by mass of each element:**
- %Ca:
\[
\text{%Ca} = \left(\frac{120.24}{310.18}\right) \times 100 \approx 38.8\%
\]

- %P:
\[
\text{%P} = \left(\frac{61.94}{310.18}\right) \times 100 \approx 20.0\%
\]

- %O:
\[
\text{%O} = \left(\frac{128.00}{310.18}\right) \times 100 \approx 41.2\%
\]

**Final results for Ca3(PO4)2:**
- **%Ca** = 38.8%
- **%P** = 20.0%
- **%O** = 41.2%

### Summary:
- For **CClF3**: %C = 20.6%, %Cl = 30.4%, %F = 49.0%
- For **Ca3(PO4)2**: %Ca = 38.8%, %P = 20.0%, %O = 41.2%