1. The image represents the reaction between a certain number of molecules of H2 and O2.

Two squares are shown. Inside the left square two units of two joint circles if shown. The molecular formula of hydrogen gas is shown on top of this square. The square on the right has three units of two joint circles. The molecular formula for oxygen gas is shown on top of this square

If the maximum amount of H2O is formed during the reaction, what is the leftover reactant?

One molecule of H2
Two molecules of H2
One molecule of O2
Two molecules of O2

2. How many moles of water are produced when 5 moles of hydrogen gas react with 2 moles of oxygen gas?

Balanced equation: 2H2 + O2 → 2H2O

2 moles of water
4 moles of water
5 moles of water
7 moles of water

3. One mole of copper has a mass of 63.5 grams. Approximately how many atoms of copper are present in one mole of copper?

63 atoms
64 atoms
32 × 1023 atoms
6 × 1023 atoms