### Video Transcript

In a chemical reaction, 64 grams of
zinc is reacted with excess oxygen to form 80 grams of zinc oxide. How much oxygen is used in this
reaction?

The reaction occurring involves
zinc as a reactant. It is reacted with a second
reactant, oxygen. This produces one product, zinc
oxide. The reaction started with 64 grams
of the element zinc. The zinc reacts with excess
oxygen. This means that there is more than
enough oxygen available to completely react with all of the zinc. We are told that 80 grams of the
product is produced. This reaction occurs between solid
zinc and the oxygen in the air to produce zinc oxide, which often forms as a layer
on the zinc metal.

To find out how much oxygen in the
excess was used to form this product, we can use the law of conservation of
mass. It states that mass is neither
created nor destroyed in a chemical reaction, which means the sum of the reactant
masses must equal the sum of the product masses. Using this idea, we can set up an
expression to find the mass of the oxygen used. We know the sum of the reactant
masses must equal the sum of the product masses. So the 64 grams of zinc plus the
amount of oxygen used, which we can set as 𝑥, must equal the mass of the products,
which is 80 grams of zinc oxide.

To solve for 𝑥, we can subtract 64
grams from each side. On the left side of the equation,
64 grams minus 64 grams will equal zero. This will leave 𝑥 on the left side
of the equation. And when we subtract 64 grams from
80 grams, we get 16 grams. This is the amount of oxygen
used. Therefore, the mass of oxygen used
in this reaction is 16 grams.