Moles

Question 1

Mole

Answer 1

The amount of substance that contains the same number of particles that 12g of carbon 12 has of atoms

Question 2

Avogadros constant

Answer 2

Number of atoms in exactly 12g of carbon 12
Which is 6.022x10²³

Question 3

What is the molar mass of a substance?

Answer 3

The mass of one mole of that substance
Which is the same value as the Ar or Mr
Expressed in gmol⁻¹

Question 4

Why do we use moles?

Answer 4

As a form of counting the amount of atoms in a substance
Which to do would be impossible and use very big numbers
So use this idea of moles to scale up and therefore use numbers easier to deal with

Question 5

How to find number of moles from mass?

Answer 5

Mass
———
Mr/ Ar

Question 6

What can moles be made up of?

Answer 6

Anything, such as atoms, ions, molecules, electrons

Question 7

How do you find the number of atoms in a substance when given the mass of it?

Answer 7

Find number of moles of it by doing mass/Mr or Ar
Multiply the number of moles by avogadros constant

Question 8

What represents avogadros constant?

Answer 8

L

Question 9

Formula for number of atoms/molecules/ions etc

Answer 9

Avogadros constant x number of moles

Question 10

How to find the mass of a specific number of atoms/molecules/ions etc?

Answer 10

Divide the number of particles by avogadros constant to find the number of moles
Multiply that by the Mr/Ar to find the mass

Question 11

What to remember when writing equations?

Answer 11

Make sure they are balanced (can use fractions as big numbers)
Use state symbols if necessary
Determine whether reaction is reversible or not

Question 12

Ionic equations

Answer 12

An equation which shows any atom/ molecules involved
But only the ions that react together
And no spectator ions

Question 13

Spectator ions

Answer 13

Ions that are there before and after the reaction but are not involved in the reaction

Question 14

How to write ionic equations?

Answer 14

1) Replace all the compounds/elements as ions
leave molecules eg co2 as is
2) cross out identical ions (spectator ions) on both side
3) rewrite to be only remaining ions left and as aqueous

Question 15

Remaining ions in an ionic equation

Answer 15

Ions that reacted with each other to form a New Ionic compound
And existed as something else before reaction

Question 16

When might there be no ionic equation?

Answer 16

If all the products and reactants are aqueos then there is no change in ions charge/bonding so no ionic equation

Question 17

Ionic half equation

Answer 17

A type of reaction that involves only one reactant and shows the gain or loss of electrons from it

Question 18

When are ionic half equations written?

Answer 18

Involving oxidation or reduction

Question 19

Reacting masses according to ratio (no moles included)

Answer 19

If the molar ratio is given when can see the ratio of products to reactants
Then if given the mass of 1 mole can work out the masses of the other species given the ratio

Question 20

How can we use reacting masses to determine the ratio the reactants react in thus the equation?

Answer 20

Calculate the number of moles using information given
Simply this to simplest whole number ratio

Question 21

When might we need to use reacting masses to find the equation of a reaction

Answer 21

When a salt exists as hydrates where we aren’t sure of the number before which therefore may affect the equation.

Question 22

Hydrate

Answer 22

A compound that contains water of crystallisation

Question 23

Molar mass/Mr of a hydrate

Answer 23

Normally calculate the mr of the compound then multiply the mr of water by how many are present in the hydrate