In the chemical reaction below, calcium (Ca) and water (H2O) react to form calcium hydroxide (Ca(OH)2) and hydrogen gas (H2).

Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g)

Calcium and water are the reactants in this chemical reaction, whereas calcium hydroxide and hydrogen gas are the products that are formed. Once the reaction reaches completion,

A.
the total mass of the products will be greater than the original mass of the reactants.
B.
the total mass of the products will be equal to the original mass of the reactants.
C.
the products of the reaction will have changed back into the reactants.
D.
the total mass of the products will be less than the original mass of the reactants.

Option B) the total mass of the products will be equal to the original mass of the reactants.

Explanation:

At completion, the equation

Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) can be said to be at equilibrium (i.e mass of reactants will equal that of products formed). So, the law of conservation of mass has been obeyed since the mass of the entire system is conserved.

Thus, the total mass of the products will be equal to the original mass of the reactants.

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