Chemical Quantities

Calculate the mass of compounds.

Calculate the volume of a given mass of a gas from its density at a given temperature and pressure.

Calculate the molar volumes of gases from their densities at a given temperature and pressure and compare the calculated volumes.

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

Avogadro (1776-1856)

Any sample of any gas at the same temperature and pressure will contain the same number of particles.

Defined 22.4 L as the molar volume for any gas.

Particles are now counted in moles (n).

The molecular mass of water is 18.0 µ ...

One mole of any particle has a mass equal to its total atomic/formula/molecular mass – IN GRAMS (g).

One mole of aluminum atoms has a mass of 27.0 g.

So...the molar mass of water is 18.0 g/mol.

The mass of one mole is called the molar mass - units are grams per mole (g/mol)

What is the molar mass of ammonium dichromate?

Determine the molar mass.

1 mole of (NH4)2Cr2O7 = 2 N + 8 H + 2 Cr + 7 O

= 2(14.0g/mol)+ 8(1.0g/mol)+ 2(52.0g/mol)+ 7(16.0g/mol)

(NH4)2Cr2O7 = 252.0 g/mol

(NH4)2Cr2O7

Calculating MolesAnd the Factor Label Line

Dimensional Analysis is used to organize calculations, ratios, and to choose the right units for the answer.

Rules for using a Factor Label Line

1. Start with what you know2. Put the unit you want to get rid of on the bottom3. Put the unit you want on the top4. Multiply across the top, Divide across the bottom

What is the mass of 1.20 x 10–5 moles of carbon tetrachloride, CCl4?

CCl4 = 1 C + 4 Cl = 1(12.0 g/mol) + 4(35.5 g/mol) = 154.0 g/mol

or154.0 g1 mole

1.20 x 10-5 mol 1 mol

154.0 g

154.0 g1 mole

1.85 x 10-3 g

1. 5.00 moles of aluminum atoms.2. 100.0 g of sugar, C11H22O11

3. 7.25 moles of iron (III) oxide.4. 1.42 x 10-3 g of copper (II) sulphate.

1. Al = 27.0 g/mol = 135 g 2. C11H22O11 = 330.2 g/mol = 0.303 mol3. Fe2O3 = 159.6 g/mol =1160 g 4. CuSO4 = 159.6 g/mol = 8.90 x 10-6

mol

Calculating the Number of Particles

We call this - Avogadro's Number

In one mole there is 6.02 x 1023 particles.

One mole contains 6.02 x 1023 of anything

6.02 x 1023 pencils is 1 mole of pencils6.02 x 1023 carbon atoms is 1 mole…6.02 x 1023 water molecules is 1 mole…

One mole of anything is 6.02×1023

The term "particles" refers to any individual thing like atoms, formula units, molecules, ions, etc.

or6.02 x 10 23 particles 1 mole 6.02 x 10 23 particles

1 mole

particles.

How many atoms in 25.0 moles of copper?

25.0 mol Cu1.51 x 10 25 atoms=

How many molecules of water in 1.50 x 10–5 moles?

= 9.03 x 10 18 molecules of water

1.50 x 10–5 mol H2O

6.02 x 10 23 particles

1 mole

6.02 x 10 23 particles

1 mole

How many moles is 5 atoms of zinc?

5 atoms of Zinc is 8.31 x 10–24 moles.

5 atoms Zn= 8.31 x 10-24 moles

6.02 x 10 23 particles

1 mole

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

How many molecules of water in a 10.0 g sample of water?

0.556 mol H20=1 mole18.0 g

10.0 g H2O

0.556 mol H2O 6.02 x 10 23 particles

1 mole

= 3.34 x 10 23 molecules H20

we can put the two equations together

There are 3.34 x 1023 molecules in 10.0 g of water.

1 mole6.02 x 10 23 particles of H2O10.0 g H2O

18.0 g1 mole

= 3.34 x 10 23 molecules H20

How many atoms in 25.0 g of sodium chloride?

NaCl = 58.5 g/mol

= 5.14 x 10 23 atoms

1 mole6.02 x 10 23 For.U 25.0 g NaCl

58.5 g1 mole 2 atoms

1 For. U

The formula mass, in amu, is the sum of the atomic masses of all atoms in one substance.

The molar mass of a substance is the mass of one mole of that substance, or its formula mass in grams. The mole is equal to 6.02 x 1023 particles - Avogadro’s Number.

Using molar mass, we can move between moles, mass, particles of a given substance.