Science Quick Check. 1 correct answer per question.

Question

1. Use the chemical reaction to answer the question.

​CaCO3→CO2​+CaO

A scientist heats 30 grams of calcium carbonate ( CaCO3
) in the chemical reaction shown. What is the total mass of the products?
a. 60 grams
b. 15 grams
c. 30 grams
d. 10 grams

2. Use the chemical reaction to answer the question.

4​Fe+3O2→2Fe2O3​

What happens to atoms of Fe and O2 during the reaction?
a. They gain mass.
b. They maintain their properties.
c. They are rearranged.
d. They are lost.

3. Use the chemical reaction to answer the question.

NaHCO3+HC2H3O2→NaC2H3O2+H2O+CO2

A student mixes baking soda ( NaHCO3
) and acetic acid ( HC2H3O2
) to produce a chemical reaction shown. Which statement about the reaction is correct?
a. The atoms of the reactants are regrouped during the reaction.
b. Some atoms gain mass after the reaction.
c. There are more H atoms after the reaction.
d. Atoms of Na are destroyed during the reaction.

4. Use the chemical reaction to answer the question.

2H2+O2→2H2O

There are four atoms of hydrogen ( H
) before the reaction. How many atoms of hydrogen are present after the reaction?
a. 2
b. 8
c. 4
d. 5

Answer 1

Here are the correct answers for each question:

1. The total mass of the products in a chemical reaction is equal to the total mass of the reactants (law of conservation of mass). Therefore, the answer is: c. 30 grams

2. During a chemical reaction, atoms are rearranged to form new substances. Therefore, the answer is: c. They are rearranged.

3. In a chemical reaction, the atoms of the reactants are regrouped to form products but their total count remains the same. Therefore, the answer is: a. The atoms of the reactants are regrouped during the reaction.

4. The number of hydrogen atoms remains the same before and after the reaction, so if there are four hydrogen atoms before, there will still be four after. Therefore, the answer is: c. 4