1.Use the Ideal Gas Law to solve a gas stoichiometry problem.

2 H 2 O 2 (l) ---> 2 H 2 O (g) + O 2 (g) Decompose 1.1 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the volume of O 2 at STP? Bombardier beetle uses decomposition of hydrogen peroxide to defend itself.

2 H 2 O 2 (l) ---> 2 H 2 O (g) + O 2 (g) Decompose 1.1 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the volume of O 2 at STP? Solution 1.1 g H 2 O 2 1 mol H 2 O 2 1 mol O L O 2 34 g H 2 O 2 2 mol H 2 O 2 1 mol O 2 34 g H 2 O 2 2 mol H 2 O 2 1 mol O 2 = 0.36 L O 2 at STP

How many grams of He are present in 8.0 L of gas at STP? = 1.4 g He 8.0 L He x 1 mol He 22.4 L He x 4.00 g He 1 mol He

Gas Stoichiometry Trick If reactants and products are at the same conditions of temperature and pressure, then mole ratios of gases are also volume ratios. 3 H 2 (g) + N 2 (g)  2NH 3 (g) 3 moles H mole N 2  2 moles NH liters H liter N 2  44.8 liters NH 3

Gas Stoichiometry Trick Example How many liters of ammonia can be produced when 12 liters of hydrogen react with an excess of nitrogen in a closed container at constant temperature? 3 H 2 (g) + N 2 (g)  2NH 3 (g) 12 L H 2 L H 2 = L NH 3 L NH

 1. You will need to use PV = nRT

Gas Stoichiometry Example on HO How many liters of oxygen gas, at 1.00 atm and 25 o C, can be collected from the complete decomposition of 10.5 grams of potassium chlorate? 2 KClO 3 (s)  2 KCl(s) + 3 O 2 (g) 10.5 g KClO 3 1 mol KClO g KClO 3 3 mol O 2 2 mol KClO mol O 2

Gas Stoichiometry Example on HO How many liters of oxygen gas, at 1.00 atm and 25 o C, can be collected from the complete decomposition of 10.5 grams of potassium chlorate? 2 KClO 3 (s)  2 KCl(s) + 3 O 2 (g) 3.2 L O 2 (1.0 atm)(V)( atm*L / mol*K )(298 K)(0.13 mol)

1.Explain Dalton’s Law and use it to solve a problem. 2.Use the Ideal Gas Law to solve a gas density problem. 3.Use the Ideal Gas Law to solve a gas stoichiometry problem.

Highdensity Lowerdensity 22.4 L of ANY gas AT STP = 1 mole

Gas Density … so at STP…

Density and the Ideal Gas Law Combining the formula for density with the Ideal Gas law, substituting and rearranging algebraically: M = Molar Mass P = Pressure R = Gas Constant T = Temperature in Kelvins

Gas Stoichiometry #4 How many liters of oxygen gas, at 37.0  C and atmospheres, can be collected from the complete decomposition of 50.0 grams of potassium chlorate? 2 KClO 3 (s)  2 KCl(s) + 3 O 2 (g) = “n” mol O g KClO 3 1 mol KClO g KClO 3 3 mol O 2 2 mol KClO 3 = mol O 2 = 16.7 L

How many L of O 2 are needed to react 28.0 g NH 3 at 24°C and atm? 4 NH 3 (g) + 5 O 2 (g) 4 NO(g) + 6 H 2 O(g)