Question

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. 8
b. 2
c. 5
d. 4

Answer 1

The chemical equation 2H2 + O2 -> 2H2O shows that there are 2 molecules of hydrogen (H2) involved in the reaction.

Each molecule of hydrogen (H2) consists of 2 atoms of hydrogen.

Therefore, before the reaction, there are 2 molecules of H2 x 2 atoms of H = 4 atoms of hydrogen.

After the reaction, the 2H2 molecules combine to form 2 molecules of H2O.

Each molecule of water (H2O) consists of 2 atoms of hydrogen.

Therefore, after the reaction, there are 2 molecules of H2O x 2 atoms of H = 4 atoms of hydrogen.

The answer is d. 4.