Mole Conversions

1 mol = __ grams    (add up the mass of the formula)

1 mol = 6.02 x 10²³ atoms, molecules, etc.

1 mol = 22.4 L of gas @ 0°C and 1 atm pressure.

These conversions work just like the ones from earlier in the year.  Some examples:

1.) 2.5 mol of NH₃ gas occupies what volume at 0°C and 1 atm?

2.5 mol NH3	22.4 L gas
1	1 mol gas

2.5 × 22.4 L NH₃ = 56.0 L NH₃

2.) What is the mass of 4.1 mol NH₃ gas?

The molar mass is (1 × 14) + (3 × 1) = 17 g, so 1 mol NH₃ = 17 g NH₃.

4.1 mol NH3	17 g NH3
1	1 mol NH3

4.1 × 17 g NH₃ = 69.7 g NH₃

3.) How many molecules are there in 0.75 mol of NH₃ gas?

0.75 mol NH3	6.02 × 10^23 molecules
1	1 mol

0.75 NH₃ × (6.02 × 10²³ molecules) =

4.52 × 10²³ molecules NH₃

4.) What is the volume of 25.5 g of NH₃ gas at 0°C and 1 atm?

1 mol NH₃ = (1 × 14) + (3 × 1) = 17 g

25.5 g NH3	1 mol NH3	22.4 L
1	17 g NH3	1 mol

 33.6 L NH₃

Note:  this chapter is a good time to start including the chemical formula in the units.  This will be extremely useful in the next chapter (stoichiometry).