Question 8 Unsaved Mrs. Johnson's science class perform an experiment. They combine two substances that react with lots of fizzing and bubbling. The class determines the mass of the substances before and after the experiment and find that the substances have less mass after the experiment. Hannah wants to know why the experiment didn't obey the law of conservation of mass, but Chris says it did. Who is right and why? Question 8 options: Chris is correct because the reactants and products do not have to have the same mass, but they do have to weigh the same. Chris is right because some of the mass of the reactants escaped as gas. Hannah is right because the class may have made an error in determining the mass of the substances. Hannah is right because the mass of the reactants was different than the mass of the products.

Question

Leanna Dougherty

Chemistry

15 December, 09:48

Question 8 Unsaved Mrs. Johnson's science class perform an experiment. They combine two substances that react with lots of fizzing and bubbling. The class determines the mass of the substances before and after the experiment and find that the substances have less mass after the experiment. Hannah wants to know why the experiment didn't obey the law of conservation of mass, but Chris says it did. Who is right and why? Question 8 options: Chris is correct because the reactants and products do not have to have the same mass, but they do have to weigh the same. Chris is right because some of the mass of the reactants escaped as gas. Hannah is right because the class may have made an error in determining the mass of the substances. Hannah is right because the mass of the reactants was different than the mass of the products.

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Answers (2)

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Fitzgerald · Answer 1

Chris is right because some of the mass of the reactants escaped as gas.

During the experiment, they combine two substances that react with lots of fizzing and bubbling. The fizzing and bubbling mean that a gas is created from the substances. As the gas is not captured to determine its mass, the total mass after experiment is less.

Joslyn Nguyen · Answer 2

Answer: Chris is right because some of the mass of the reactants escaped as gas.

Explanation:

The law of conservation of mass is a universal law: it is obeyed always.

Since when the two substances were combined they reacted with lots of fizzing and bubbling, it is clear that some gas was formed. This is, one or more products were in the form of gas.

In this case, the law of conservation of mass leads to the conclusion that part of the original mass contained in the reactant substances ended in the products that escaped as gas.

In fact, if all the measurements were made carefully, the difference of the masses before and after the reaction corresponds exactly to the mass of the products that evolved as gas and were not collected. This is, the law of conservation of mass permits to calculate the mass of the gaseous products that couldn't be directed determined because the gases were not confined inside the walls of a vessel.