AVOGADRO’S LAW

Volume and Moles

Avogadro’s Law When the number of moles of gas is

doubled (at constant temperature and pressure, the volume doubles.

The volume of gas is directly proportional to the number of moles if temperature and pressure remain constant

Avogadro’s Law is written:

ORn = number of molesV = Volume

As the number of moles increases, the volume increases and the temperature and pressure remain the same

Using Avogadro’s LawSuppose we have a 12.2-L sample containing 0.50 mol of Oxygen gas at a pressure of 1 atm and temperature of 25 oC. If all of this O2 is converted to ozone, O3, at the same temperature and pressure, what will be the volume of ozone formed?

Step 1: Use a balanced equation to determine the mole ratio.

Step 2: Calculate the number of moles of O3 that will be produced

Step 3: Use the equation and determine the initial and final conditions

Step 4: Solve

3O2 2O3

Avogadro’s Law Practice Problems:1. If 0.105 mol of hydrogen gas occupies a volume of 2.35 L at a certain

temperature and pressure what volume would 0.337 mol of hydrogen gas occupy under the same conditions?

2. If 1.00 mol of helium occupies a volume of 22.4 L at 273 K and 1.00 atm, what volume will 1.00 g of helium occupy under the same conditions?

3. If 3.25 mol of argon gas occupies a volume of 100.0 L at a particular temperature and pressure, what volume does 14.15 mol of argon occupy under the same conditions?

4. If 2.71 g of argon gas occupies a volume of 4.21 L, what volume will 1.29 mol of argon occupy under the same conditions?

5. If 1.5 mol of nitrogen gas (N2) has a volume of 36.7 L and a second sample has a volume of 16.5 L under the same temperature and pressure conditions. How many moles of Nitrogen gas are there in the second sample?