section+1+d

back to IGCSE chemistry

** In this section you will be assessed on your ability to **
1.16 calculate relative formula masses (//M////r//) from relative atomic masses (//A////r//) 1.17 understand the use of the term mole to represent the amount of substance 1.19 carry out mole calculations using relative atomic mass(//A////r//) and relative formula mass (//M////r//)
 * 1.18 understand the term mole as the Avogadro number of particles (atoms,molecules, formulae, ions or electrons) in a substance**
 * 1.20 understand the term molar volume of a gas and use its values (24 dm3 and 24,000 cm3) at room temperature and pressure (rtp) in calculations**

= Section notes = = Investigations = = Resources =

Textbook pages

 * 1) moles and relative masses: chapter 22 page 176 to 182
 * 2) molar volume: chapter 23 page 189 and 190

Tutorials
[|Calculating moles, masses and number of particles] [|Key mole concepts] = Lesson = __ Mole __ Used to measure the amount of a chemical. [|TED presentation on mole]

__ Relative formula mass: __
The mass of a compound compared to the mass of a C-12 atom (the most abundant carbon isotope) and is calculated by adding the relative atomic mass, multiplied by the number of atoms, of the elements in the compound.
 * 1) study the 4 examples on page 1 of the 1d handout
 * 2) do question (a) to (m) on page 1 on handout 1d
 * 3) worksheet below:
 * on page 47 answer questions 1 to 24;
 * on page 48 answer questions 1 to 5, 21 to 30 and 41 to 50

__ Calculating moles and masses __
The molar mass of a substance is the mass of 1 mole of that substance which is the relative mass of the substance expressed in grams.
 * 1) Calculating moles using mass: find the formula on page 2 of 1d handout or on the worksheet attached below.
 * 2) Go to http://www.echalk.co.uk/ (remember username is echalk2@dulwich-shanghai.cn; password is echalk) and go to section "Chemical formulae, equations and calculations" and "introducing the mole": do both activities to practice calculating moles.
 * 3) Do questions on page 2



__ Calculating moles and molar volumes __
You can also calculate the number of moles easily of a gas because 1 mole of a gas is always 24 dm3 or L, for any gas. See handout 1d. Answer the questions at the bottom of page 2 of handout 1d.

__ Calculating molar volumes and masses __
You will be asked to convert mass of a gas into a volume. This cannot be done directly so 'moles' will be the link. On the worksheet below answer questions 1, 2, 3 and 4.