1. Mole-Mass and Mole-Volume Relationships
10.2
Page 297

2. The Mole-Mass Relationship
Remember! The molar mass of any substance is the mass in grams of one mole of the substance.
What is the molar mass of oxygen? 32g or 16g?
Avoid confusion by using the formula, O₂ or O.

3. Measuring the Mol in Lab
Use the molar mass of an element or compound to convert between the mass of a substance and the moles of a substance.
Conversion factor is the relationship: molar mass = 1 mol
Mass (grams) = Number of moles x mass (grams)/1 mole

4. Mass of NaCl = 3.00 mol x 58.5g/1mol = 176 g
The molar mass of NaCl is 58.5g/mol, so the mass of 3.00 mol NaCl is calculated in this way.
Mass of NaCl = 3.00 mol x 58.5g/1mol = 176 g
Complete Sample Problem pg. 298/299

5. The Mole-Volume Relationship
The volumes of one mole of different sold and liquid substances are NOT the same.
The volumes of moles of gases, measured under the same physical conditions, are much more predictable.

6. Avogadro’s Hypothesis
States that equal volumes of gases at the same temperature and pressure contain equal numbers of particles.
Because volumes of gases are effected by changes in temperature and pressure, volumes of gases are usually measured at standard temperature and pressure (STP).
Temperature of 0 degrees C
Pressure of 101.3kPa, or 1 atmosphere (atm)

7. Mole-Volume Relationship
At STP, 1 mole or 6.02 x 10²³ representative particles, of any gas occupies a volume of 22.4 Liters.
The quantity, 22.4L, is called the molar volume of a gas.

8. Calculating Volume at STP
Conversion factor for volume of gas at STP is 22.4L = 1 mol at STP
Volume of gas = moles of gas x 22.4L/1mol
Complete Sample Problem 10.7 page 301

9. Calculating Molar Mass from Density
Different gases have different densities.
Density of a gas is measured in grams per liter (g/L) and at a specific temperature.
Molar mass = density at STP x 22.4/1mol
Complete Sample Problem 10.8 page 302

10. The mole is at the center of your chemical calculations
The mole is at the center of your chemical calculations. To convert from one unit to another, you must use the mole as an intermediate step.