Chemical Quantities

· Calculate the mass of compounds.

· Calculate the molar volumes of gases.

· Solve problems requiring conversions between mass, and number of particles, and moles.

The mole allows the conversion between mass and number of particles.

In one mole there is 6.02 x 1023 particles.

22.4 L

Molar Volume

Avogardo (1776-1856)

Avogadro’s Hypothesis - any sample of any gas at the same temperature and pressure will contain the same number of particles.

Chemists use a standard temperature and pressure, STP, to measure gas volumes.

0°C and 101.3 kPa

At STP:The volume of 1 mole of ANY GAS is 22.4 L.

22.4 L/mol is known as molar volume.

The MASS of 22.4 L of any gas is equal to themolar mass for that gas.

How many moles are in 50.0 L of Fluorine gas atSTP?

F2 = 36.0 g/mol

50.0 L22.4 L1 mol = 2.23 mol

What is the STP volume of 10.0 g of Methane gas?

CH4 = 16.0 g/mol

10.0 g16.0 g1 mol = 14.0 L

1 mol 22.4 L

Density: A physical property that describes the mass per unit volume of a substance.

grams (g) per litregrams per mL (or cm3)

Calculate the volume, in litres, of one mole ofammonia (NH3) at room temperature if the densityis 0.696 g/L.

NH3 = 17.0 g/mol

1 mol 1 mol

17. 0 g= 24.4 L 0.696 g

1 L

Calculate the volume, in litres, of two moles of carbon dioxide, at room temperature, when the density is 1.80 g/L.

CO2 = 44.0 g/mol

2 mol 1 mol

44. 0 g= 48.9 L 1.80 g

1 L

· STP 0°C and 101.3 kPa (1 atm).

· At STP, the molar volume of any gas is 22.4 L(L/mol)

· Molar mass = total grams in 1 mole g(/mol).

· 1 mole = 6.02 x 1023 particles (Avogadro)

· density of a substance = mass per volumeg (/L)

· All roads lead to moles (convert to moles first).