find the reaction of Cu(s)+O2(g)⟶

Answer 1

2Cu + O2 => 2CuO

This is a combination or synthesis reaction. Where Cu is combined with the O2 to give CuO (solid).

A + B => AB

Cu + O2 => CuO (Unbalanced)

To balance:

Step 1: We have 2 oxygens on the left, so I have to include a 2 in front of CuO

Cu + O2 => 2CuO

Step 2: Now that the oxygens are balanced, I look at the Cu and notice I have 1 Cu on the left and 2 Cu on the right. Thus, I write a 2 in front of my Cu on the left, giving me

2Cu + O2 => 2CuO