MODULE 2 - 2.1.2 and 2.1.3 compounds, formulae, equations, amount of a substance

Question 1

How are ions created?

Answer 1

Electrons and transferred from one atom to another to form compounds.

Question 2

How to work out the formula of an ionic compound:

Answer 2

1. Write ions e.g Ca2+ and NO3-
2. Swap the charges to Ca- and NO3 2+
3. Drop the charges to Ca and NO3 2
4. Simplify to whole number ratio if needed to Ca(NO3)2

Question 3

What are salts

Answer 3

Ionic compounds. Can be hydrated or anhydrous

Question 4

How do you calculate water of crystallisation?

Answer 4

1. Write out the 2 molecules involved
2. Write their masses
3. Divide the mass by the Mr to get n
4. Divide the numbers by the smallest number of moles to get moles of water of crystallisation

Question 5

What are ions that don’t get involved in a reaction

Answer 5

Spectator ions

Question 6

How do you write an ionic equation?

Answer 6

Write out the number of ions then cancel any ions that appear on both sides of the equation for the simplest ionic equation

Question 7

What is Avogadro’s number

Answer 7

1 mole = 6.02x10 (23) mol-1

Question 8

How do you calculate the number of particles?

Answer 8

Number of particles = Avogadro’s number x number of moles

Question 9

What is the mole equation for mass and mr?

Answer 9

number of moles = mass/mr

Question 10

What is the mole equation for solutions?

Answer 10

Number of moles = concentration (moldm-3) x volume (dm3)

Question 11

What is the mole equation for the ideal gas equation?

Answer 11

pV = nRT

Question 12

What are the units for the ideal gas equation?

Answer 12

p= pressure (Pa)
V= volume (m3)
n= moles (mol)
R= gas constant (8.31kJ mol-1)
T= temperature (K)

Question 13

What are the standard conditions?

Answer 13

298K and 100kPa

Question 14

What is the empirical formula

Answer 14

The simplest whole number ratio of elements in a compound

Question 15

How do you calculate percentage yield?

Answer 15

% yield = actual / theoretical x 100

Question 16

Reasons for not obtaining the theoretical yield?

Answer 16

1. Reaction has not gone to completion
2. Side reactions
3. Purification results in loss of product

Question 17

What is a limiting reagent

Answer 17

The reactant that is not in excess and will be used up first

Question 18

How do you calculate atom economy?

Answer 18

Atom economy = Mr of desired product / sum of Mr of all products x 100

Question 19

What is the atom economy?

Answer 19

A measure of how well atoms have been utilised

Question 20

What is the molecular formula?

Answer 20

The number and type of atoms of each element in a molecule

Question 21

What are features of reactions with high atom economies?

Answer 21

1. Produces a large proportion of desired products and less waste products
2. Important for sustainability