Question

A solid mass of 20 g is mixed with 30 g of solution in an open container with a mass of 50 g. When the two are mixed, they fizz. The mass of the entire system is taken after the experiment is completed and found to be 95 g. Does this obey the law of conservation of mass? Why or why not? How would you explain what happened?

Answer 1

The law of conservation of mass states that in a chemical reaction, mass is conserved and can neither be created nor destroyed. The missing mass in the given experiment with fizzing is actually gas released into the atmosphere, not a violation of the law. Examples like baking bread, burning magnesium, and Lavoisier's experiments all support the law of conservation of mass.

Step-by-step explanation:

The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction. When a solid mass of 20 g is mixed with a 30 g solution in an open container that itself has a mass of 50 g, we would expect the total mass after the reaction to be the same as before, according to this law. If the initial total mass was 100 g (20 g + 30 g + 50 g container) and the final measured mass is 95 g, it appears that the law has been violated. However, the fizzing indicates a gas was produced that escaped into the atmosphere, which accounts for the missing mass. Therefore, the law of conservation of mass is not violated; instead, the experiment setup didn't account for the gaseous products that were not contained.

Looking at the broader application of this law:

• (a) When bread dough is baked, the mass of the bread will be less than that of the original dough because gases like water vapor and carbon dioxide are released during the baking process.
• (b) When magnesium burns, the resulting magnesium oxide will have a greater mass than the original magnesium because it has combined with oxygen from the air.
• (c) Lavoisier's sealed flask containing tin and air heated to form tin oxide would remain the same mass before and after the reaction, as no matter can enter or leave the sealed system.

These three examples, along with the initial experiment, all relate back to the conservation of mass in chemical reactions, where the total mass of the reactants equals the total mass of the products. This fundamental principle was established through quantitative analysis and accurate measurements in chemistry.