Question

Using this equation, how many hydrogen atoms are shown on the reactant side? 2H₂+O₂→2H₂O

a. 2
b. 4
c. 6
d. 8

Answer 1

b. 4

Step-by-step explanation:

There are 2 H2 molecules. Each H2 molecule is made up of 2 hydrogen atoms. If there are 2 H2 molecules, 2 x 2 = 4 total hydrogen atoms on the reactant side.

Answer 2

On the reactant side of the equation, there are 2 hydrogen atoms.

Step-by-step explanation:

When we count the number of atoms of both elements, shown under the equation, we see that the equation is not balanced. There are only 2 atoms of hydrogen on the reactant side of the equation, while there are 4 atoms of hydrogen on the product side. We can balance the above equation by adding a coefficient of 2 in front of the formula for hydrogen.

A coefficient is a small whole number placed in front of a formula in an equation in order to balance it. The 2 in front of the H₂ means that there are a total of 2 × 2 = 4 atoms of hydrogen as reactants. Visually, the reaction looks like the figure below.