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. 10 grams
B. 15 grams
C. 30 grams
D. 60 grams

Use the chemical reaction to answer the question. ​Fe+O2→Fe2O3​ What happens to atoms of Fe and O2 during the reaction?
A. They are lost.
B. They maintain their properties.
C. They are rearranged.
D. They gain mass.

What is most likely to occur during a chemical reaction?
A. Molecules of the original substance are lost.
B. Mass is conserved.
C. The original substance maintains its properties.
D. New atoms are created.

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. There are more H atoms after the reaction.
B. The atoms of the reactants are regrouped during the reaction.
C. Atoms of Na are destroyed during the reaction.
D. Some atoms gain mass after the reaction.

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. 5
B. 4
C. 2
D. 8
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