Question

Calculate the mass of oxygen produced from the decomposition of 75.0 g of potassium chlorate. 2KClO3 --> 2KCl + 3O2.

Answer 1

To calculate the mass of oxygen produced from the decomposition of potassium chlorate (KClO3), we can follow these steps:

1. **Write down the balanced chemical equation**:
\[
2 \text{KClO}_3 \rightarrow 2 \text{KCl} + 3 \text{O}_2
\]

2. **Calculate the molar mass of potassium chlorate (KClO3)**:
- Potassium (K): 39.10 g/mol
- Chlorine (Cl): 35.45 g/mol
- Oxygen (O): 16.00 g/mol

The molar mass of KClO3 is:
\[
39.10 \, (\text{K}) + 35.45 \, (\text{Cl}) + 3 \times 16.00 \, (\text{O}) = 39.10 + 35.45 + 48.00 = 122.55 \, \text{g/mol}
\]

3. **Convert the mass of KClO3 to moles**:
Using the given mass of potassium chlorate:
\[
\text{moles of KClO}_3 = \frac{\text{mass}}{\text{molar mass}} = \frac{75.0 \, \text{g}}{122.55 \, \text{g/mol}} \approx 0.612 \, \text{mol}
\]

4. **Use the stoichiometry of the reaction to find moles of O2 produced**:
From the balanced equation, 2 moles of KClO3 produce 3 moles of O2. Thus, the ratio of KClO3 to O2 is:
\[
\frac{3 \, \text{mol O}_2}{2 \, \text{mol KClO}_3}
\]

Therefore, the moles of O2 produced from 0.612 moles of KClO3 is:
\[
\text{moles of O}_2 = 0.612 \, \text{mol KClO}_3 \times \frac{3 \, \text{mol O}_2}{2 \, \text{mol KClO}_3} = 0.918 \, \text{mol O}_2
\]

5. **Calculate the mass of O2 produced**:
The molar mass of O2 (oxygen gas) is:
\[
2 \times 16.00 \, \text{g/mol} = 32.00 \, \text{g/mol}
\]

Now, we can find the mass of O2 produced:
\[
\text{mass of O}_2 = \text{moles of O}_2 \times \text{molar mass of O}_2 = 0.918 \, \text{mol} \times 32.00 \, \text{g/mol} \approx 29.376 \, \text{g}
\]

6. **Final answer**:
\[
\text{The mass of oxygen produced is approximately } 29.4 \, \text{g}.
\]

Thus, the mass of oxygen produced from the decomposition of 75.0 g of potassium chlorate is approximately **29.4 g**.