Question

During an investigation a scientist burned 48 g of magnesium strip. After the reaction the total mass of the product formed was found to be 80 g. Does the law of conservation of mass hold true in this case? Use complete sentences to justify your answer based on numerical calculations.

Answer 1

Answer:

Explanation:

yes, the law of conservation of mass hold true in this case

burning magnesium strip is explained by this equation

2 Mg (s) + O2 (g) -> MgO (s)

So the lighter magnesium, after reacting with oxygen in air, forms the heavier magnesium oxide. molar mass of magnesium and magnesium oxide are 24g and 40g respectively. So the same ratio 24:40 (i.e. 3:5) is maintained in the given masses of 48g and 80g, which means mass is conserved in the reaction.

Answer 2

Answer:

The law of conservation of mass applies to both cases

      When 50 g of sugar undergoes a physical change, say for example  melting, the amount of sugar in the solution or melted form will also be 50 grams. This shows that the mass before and after the change was the same, in accordance to the law of conservation of mass. The mass stays the same.

When the magnesium strip is burned, this is a chemical reaction. The problem is that we only measure the mass of one of the substances involved in the reaction which is the magnesium strip, which makes it seem like the mass has increased. Actually, while burning, the magnesium combines with oxygen in the air. This oxygen was present before the reaction, we just did not measure it. And after the reaction it is present in the form of product. But the mass is still conserved.

Hope this helps!!:)