# Question Video: Calculating the Mass of Oxygen That Reacted with a Given Mass of Zinc to Produce a Given Mass of Zinc Oxide Science

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

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### 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.