| Example 2: When 245 grams of potassium chlorate are heated, the potassium chlorate breaks down into 78 grams of potassium, 71 grams of chlorine and some oxygen gas. Find out the mass of oxygen gas formed. | |
| Write the word equation | Potassium chlorate → potassium + chlorine + oxygen |
| Place the masses of the given substance below the equation | 245g 78g 71g ??? |
| Apply the law of conservation of mass | 245 = 78 + 71 + ? |
| Solve for the missing mass | 245 = 149 + ? 245 - 149 = ? ? = 96 |
Answer: 96g of oxygen were formed. | |