If 78.2 grams of oxygen react with copper, how many moles of copper oxide will be produced?

When copper reacts with oxygen, copper (II) oxide is formed. The reaction can be written as follows:

`Cu + O_2 -> CuO`

However, this reaction is not balanced, as the number of oxygen atoms are 2 on the reactant side, while there is only 1 oxygen atom on the product side.

The well-balanced chemical reaction for this process can be written as:

`2Cu + O_2 -> 2CuO`

Using stoichiometry, we can see that 2 moles of copper react with 1 mole of oxygen to generate 2 moles of copper oxide. 

Here, we have 78.2 g of oxygen. The molar mass of oxygen is 32 g. Hence the number of moles of oxygen are: 

78.2 g / (32 g/mole) = 78.2/32 moles

Since 1 mole of oxygen produces 2 moles of copper oxide, the number of moles of copper oxide generated are:

(78.2/32)  x 2 moles = 4.89 moles of copper oxide.

Hope this helps.