Calculation of the theoretical yield:
To determine the percentage yield of oxygen, we first need to calculate the theoretical yield of oxygen.

1. Calculate the molar mass of KClO3:
- The molar mass of K is 39.10 g/mol.
- The molar mass of Cl is 35.45 g/mol.
- The molar mass of O is 16.00 g/mol.
- Therefore, the molar mass of KClO3 is 39.10 g/mol + 35.45 g/mol + (3 * 16.00 g/mol) = 122.55 g/mol.

2. Convert the mass of KClO3 to moles:
- 61.25 g of KClO3 / 122.55 g/mol = 0.500 mol.

3. Use the balanced chemical equation to determine the molar ratio between KClO3 and O2:
- The balanced equation for the decomposition of KClO3 is: 2 KClO3 → 2 KCl + 3 O2.
- From the equation, we can see that 2 moles of KClO3 produce 3 moles of O2.
- Therefore, 0.500 mol of KClO3 will produce (0.500 mol * 3 mol O2) / 2 mol KClO3 = 0.750 mol O2.

4. Calculate the mass of oxygen:
- The molar mass of O2 is 2 * 16.00 g/mol = 32.00 g/mol.
- Therefore, the mass of oxygen produced is 0.750 mol * 32.00 g/mol = 24.00 g.

Calculation of the percentage yield:
Now that we have the theoretical yield of oxygen, we can calculate the percentage yield.

1. Determine the actual yield of oxygen:
- The actual yield is given as 18 g.

2. Calculate the percentage yield:
- Percentage yield = (actual yield / theoretical yield) * 100%.
- Percentage yield = (18 g / 24.00 g) * 100% = 75%.

Explanation:
The percentage yield is a measure of how much of the desired product is obtained compared to the maximum possible yield predicted by the balanced chemical equation. In this case, the theoretical yield of oxygen was calculated based on the given mass of KClO3, using stoichiometry and the balanced chemical equation. The theoretical yield was found to be 24.00 g. The actual yield of oxygen was given as 18 g. By dividing the actual yield by the theoretical yield and multiplying by 100%, the percentage yield was calculated to be 75%. This means that the reaction produced 75% of the maximum possible yield of oxygen. The percentage yield can be affected by various factors such as impurities in the reactants, incomplete reactions, or losses during the separation and purification processes.