c3 revision april 2015. substances can be measured in several ways. they can be: ◦ number of...

C3 revision April 2015

Substances can be measured in several ways. They can be:◦ Number of grams◦ Number of particles◦ Number of moles I mole is 1 chemical quantity

The mass of one mole of atoms is equal to the Relative Atomic Mass number (larger number on periodic table).

One mole of atoms is equal to the AVEGADRO number of particles (6.02X1023)

Remember, this is all relative to 12g of carbon-12 (so called relative atomic mass)

C3.8 Particles and Moles

To calculate the number of moles use the following formulas:

C3.8 Particles and Moles

If in doubt...... (divide by formula mass!)

1 a), e)2 d), f)3

Now try some questions- Moles

Can you do the basics? Try questions 1b, 3b, 4a, 5b and 6 Then try 2a and b (% mass) Then 7 (reacting masses) Then 9 yields and ammonia

(Do the other questions at home as part of your own revision!)

General questions 1

1. % mass of an element in a compound is

No of that type of atoms x atomic mass x 100% formula mass

e.g. Calculate %N in ammonia14/17x100%

2. For reacting mass, use the molar ratios from a balanced chemical equation

e.g. 2Mg + O2 2MgO

FM 2 x 24 + 32 2 x 4048 + 32 80

Reminder:

The actual yield is how much useful product is made in a chemical reaction.

You can calculate predicted (maximum yield) from the balanced equation.

% yield is actual yield x 100 %predicted yield

% yield is ALWAY less that 100%.Why?Always the same reasons – learn them!

Yields

Q2Q5

Have a go

You need to know what a titration is for and the step by step process.

How would you prepare a pure dry sample of a soluble salt?

You can also use a titration to calculate either the volume of concentration of one of the reagents. (You will ALWAYS be given 3 of the 4 things you need.

Use the formula

Titration questions

1. Calculate number of moles of acid used.2. Write balanced equation for reaction.3. Using moles of acid information, deduce

number of moles of base required.4. Calculate concentration of base.

This process also works the same in reverse.

C3.12 Titrations and Calculation

Q1 and Q2.Extension, Q8Try the rest at home.

Try the following:

1 mole of = 24dm3 (at room temperature and

a gas atmospheric pressure)

C3.18 Molar Volume of Gases

A GAS SYRINGE is used to collect gases during

reactions to allow molar gas calculations to be

performed

Practice your thinking on reversible reactions. You need to know that a positive energy change means endothermic and a negative energy change means exothermic.

Equilibria 1

What topics do you need to revise?

Over to you.

Tests for ions? Permanent and temporary hard water with formulae Preparing insoluble salts, two methods of preparing soluble salts Electrolysis and half equations Gas calculations Haber process Organic chemistry - making alcohols, homologous series, ethanoic acid, esters Fats, oils and soaps.