Hydrogen peroxide decomposes to water and

Question

oxygen gas by the following reaction
2H2O2(l) → 2H2O(l) + O2(g)
If 30 g of hydrogen peroxide decomposes completely, what volume of oxygen gas is formed
at STP?

1. 19.77 L
2. 22.41 L
3. 9.89 L
4. 10.79 L
5. 24.46 L

Answer 1

2H2O2(l) → 2H2O(l) + O2(g)
How many moles H2O2 in 30 g? That's moles = g/molar mass = 30/34 = ?
Look at the balanced equation. 2 mols H2O2 gives 1 mol O2; therefore ? moles H2O2 will produce ?/2 moles O2 gas.
You know that 1 mole O2 gas @ STP occupies 22.4 L. So what volume will ?/2 moles occupy?
Post your work if you get stuck.