Question

mathematical representations quick check
which statement about a chemical reaction supports the claim that mass is conserved? (1 point)
the reactants and products have the same number of substances.
the reactants and products have the same number of molecules of the same elements.
the reactants and products have the same number of elements.
the reactants and products have the same number of atoms of the same elements.

Explanation:

According to the law of conservation of mass in a chemical reaction, atoms are neither created nor destroyed. They are just rearranged. So, the key is that the number of atoms of each element remains the same in reactants and products.

• The number of substances (compounds or elements) can change. For example, \(2H_2+O_2 = 2H_2O\), number of substances changes from 2 (reactants) to 1 (product).
• The number of molecules can change. In the reaction \(2H_2+O_2 = 2H_2O\), 3 molecules (2 of \(H_2\) and 1 of \(O_2\)) react to form 2 molecules of \(H_2O\).
• The number of elements is always the same in a chemical reaction (by definition of a chemical reaction, elements are not changed into other elements in a chemical reaction), but this is not the specific reason for mass conservation. Mass conservation is about atom - level accounting.

Answer:

The reactants and products have the same number of atoms of the same elements.