1. Mole Conversions Objectives: 1. Explain how to convert between the number 2. Define molar volume of a gas. 3. Determine how to determine the number of particles in a given volume of gas at STP. Key Terms: molar volume

2. Mole the Central Unit The mole serves one very important function in scientific equations. The mole is able the measure both mass and particles. Because of this dual nature the mole is the central unit when converting from one type of measurement to the other.

3. Mole to Mass Find the molar mass of the item you wish to convert. – example: What is the mass of 2.50 mol NaCl? Determine the molar mass of the item you wish to convert and set up the conversion factor and arrange it so the unit to cancel is correctly arranged (moles are on the bottom) – example: (58.5g NaCl / 1mole NaCl ) Set up the equation and solve. 2.50mol NaCl x (58.5g NaCl / 1mol NaCl) / = 146g NaCl Given x conversion factor

4. Moles to Particles Determine the number of moles – given or as in the previous slide 11.2g NaCl x (1mol NaCl / 58.5g NaCl) = 0.191 mol NaCl Set up the conversion factor – remember that Avogadro's number is equal to the particles in a mole of a substance. (6.02 x 10 23 / 1mol) Set up the equation and solve – 0.191 mol NaCl x (6.02 x 10 23 / 1mol) = 1.15 x 10 23 NaCl ionic compounds 1.15 x 10 23 Na atoms and 1.15 x 10 23 Cl atoms or 2.30 x 10 23 total atoms

5. Molar Equivalency of Gases The mole pertains to all phases of matter. The difference between the gas and other matter is that gas will expand until it fills a container. Therefore, it is important to impose a few rules on gas in order to predict its molar mass and volume. STP - Standard Temperature and Pressure – T = 0 o C or 273K – P = 1atm or 760mmHg or 101.3kPa Under these conditions (STP) it has been experimentally proven that all gases occupy 22.4L (dm 3 ) of space.

6. Volume to Moles Find the volume of the gas you wish to convert. – 1.0L CO 2 Set up the conversion factor. – (1mol CO 2 / 22.4L CO 2 ) Set up the equation and solve. 1.0L CO 2 x (1mol CO 2 / 22.4L CO 2 ) = 0.045 mol CO 2