Question

observe the chemical equation written by an eighth grade student.
cu + 2agno₃ → cu(no₃)₂ + 2ag
which statement below correctly provides evidence that mass is conserved in this chemical equation?
a. there are two substances in the reactants and two substances formed in the products.
b. there is one copper atom in the reactants and two copper atoms in the product.
c. the number of oxygen atoms in the reactants equals the number of oxygen atoms in the products.
d. there are more nitrogen atoms present in the reactants than in the products.

Explanation:

Step1: Analyze Option A

Reactants: \( \text{Cu} \) and \( \text{AgNO}_3 \) (2 substances). Products: \( \text{Cu(NO}_3\text{)}_2 \) and \( \text{Ag} \) (2 substances). But number of substances doesn't show mass conservation.

Step2: Analyze Option B

Reactants: 1 Cu atom. Products: 1 Cu atom (in \( \text{Cu(NO}_3\text{)}_2 \)). So B is wrong.

Step3: Analyze Option C

Reactants: \( 2 \times 3 = 6 \) O atoms (from \( 2\text{AgNO}_3 \)). Products: \( 2 \times 3 = 6 \) O atoms (from \( \text{Cu(NO}_3\text{)}_2 \)). Equal O atoms show conservation (Law of Conservation of Mass: same number of each atom in reactants and products).

Step4: Analyze Option D

Reactants: \( 2 \) N atoms (from \( 2\text{AgNO}_3 \)). Products: \( 2 \) N atoms (from \( \text{Cu(NO}_3\text{)}_2 \)). So D is wrong.

Answer:

C. The number of oxygen atoms in the reactants equals the number of oxygen atoms in the products.