1.2 amount of substance

Question 1

Avogadro’s constant

Answer 1

Avogadro’s constant = 6.02 x 10^23

Question 2

General mole formula

Answer 2

Question 3

Moles and concentration

Answer 3

Question 4

The ideal gas equation

Answer 4

Question 5

Celsius to kelvin conversion

Answer 5

You might be given temperature in °C. To convert from °C to K you add 273 (e.g. 25 °C = 298 K).

Question 6

Combination of ideal gas eqn with mole = mass/mr

Answer 6

Question 7

lonic equations

Answer 7

You can write an ionic equation for any reaction involving ions that happens in solution. In ionic equations, only the reacting particles (and the products they form) are included.

Question 8

Answer 8

Question 9

Empirical and molecular formulas

Answer 9

The empirical formula gives the smallest whole number ratio of atoms of each element present in a compound. The molecular formula gives the actual numbers of atoms in a molecule. The molecular formula is made up of a whole number of empirical units.

Question 10

Answer 10

Question 11

theoretical yield

Answer 11

The theoretical yield is the mass of product that should be formed in a chemical reaction. It assumes no chemicals are ‘lost’ in the process.
You can use the masses of reactants and a balanced equation to calculate the theoretical yield for a reaction. It’s a bit like calculating reacting masses

Question 12

Calculating percentage yield

Answer 12

For any reaction, the actual mass of product (the actual yield) will always be less than the theoretical yield.
sometimes not all the starting chemicals react fully.
And some chemicals are always ‘lost’, e.g. some solution gets left on filter paper, is lost during transfers between containers, or forms other products you don’t want in side reactions.
Once you’ve found the theoretical yield and the actual yield, you can work out the percentage yield

% yield = actual yield/theoretical yield x 100

Question 13

Atom economy

Answer 13

Atom economy is a measure of the proportion of reactant atoms that
become part of the desired product (rather than by-products) in the balanced
chemical equation.

Question 14

Advantages of high atom economy

Answer 14

• Economic advantages - A company using a process that has a high atom economy will make more efficient use of its raw materials.
• Economic advantages - Using a process with a high atom economy also means that the company will have less waste to deal with.
• Environmental and ethical advantages - Processes that use fewer raw materials and produce less waste are better for the environment as well as for business.

Question 15

Calculating atom economy

Answer 15