Chapter 3, Problem 48A

Burning Candle After burning for three hours, a candle has lost half of its mass. Explain why this example does not violate the law of conservation of mass.

Interpretation Introduction

Interpretation:

Burning candle has lost half of its mass. The reason for this example to not obey the law of conservation of mass needs to be explained.

Concept introduction:

The conservation of mass, the mass remains the same at the starting and the end of the reaction.

Answer to Problem 48A

The mass of the candle is conserved if a person considers the gaseous products from the reaction.

Explanation of Solution

After burning candle from three hours, candle reduces its mass in the form of gases and ash as a product. The gas (CO₂) is released out from the reaction. It is an irreversible process. The left side reactant amount is different from the right side because mass of product reduces due to the evolution of the gas. So, it does not maintain the mass ratio between the reactant and product, and not follow the condition, the law of conservation of mass.

Conclusion

There is change in the mass ratio of the reactant and product. Burning candles do not follow the law of conservation due to the imbalanced mass of the reactant and product.