A Level Chemistry - Bonding And Calculations

Front 1

What is an isotope?

Back 1

Atoms of the same element with a different number of neutrons / different mass numbers

Front 2

What are cations?

Back 2

Positive ions

Front 3

What are anions?

Back 3

Negative ions

Front 4

What positive ions do you need to remember?

Back 4

Hydrogen = H+

Zinc = Zn2+

Silver = Ag+

Ammonium = NH4 +

Front 5

What are the negative ions you need to remember?

Back 5

Hydroxide = OH-

Sulfate = SO4 2-

Nitrate = NO3 -

Carbonate = CO3 2-

Front 6

What is the atomic number?

Back 6

The number if protons

Front 7

What is the mass number?

Back 7

The total number of Protons and neutrons

Front 8

What does the ionic charge mean?

Back 8

Ions = atoms that have lost or gained and electron and now have an overall charge

Negative charge means an atom has gained an electron to achieve a full outer shell

Positive charge means an atom has lost an electron to achieve a full outer shell

Front 9

What rules are ionic equations written with?

Back 9

Write the full balanced equation

For aqueous ionic substances write the ions separately

Leave the formulae of all solids, liquids and gases in full

Cancel all spectator ions - those that appear separately on both sides of the equation

Remember to include state symbols at the end

Front 10

What is the relative isotopic mass?

Back 10

The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Front 11

What is the relative molecular mass?

Back 11

The weighted mean mass of a molecule compared with 1/12th of the mass of an atom of carbon-12

Front 12

What is the relative atomic mass?

Back 12

The weighted mean mass of an atom of an element relative to 1/12th of an atom of carbon-12

Front 13

What other ions do you need to remember?

Back 13

Nitrite = NO2-

Hydrogen Carbonate = HCO3-

Sulfite = SO3 2-

Phosphate = PO4 3-

Front 14

How do we calculate the relative molecular mass?

Back 14

We add up all of the relative atomic masses of the atoms in the molecule

Front 15

How do you calculate the relative atom mass of an element?

Back 15

(Ab1 × mass 1) + (Ab2 × mass 2) / 100

Front 16

What is the amount of substance (n) ?

Back 16

A quantity used to count the number of particles in a substance, measured in a unit called the mole

Front 17

What is a mole?

Back 17

One mole is the amount of a substance that contains 6.02 x 10^23 particles

Front 18

What is Avogadros Constant?

Back 18

The avogadro constant is 6.02 x 10^23 mol^-1, the number of particles in each mole of carbon-12

Front 19

What is Molar mass?

Back 19

The mass in grams of one mole of the compound

Front 20

How do we calculate the molar mass of a

compound?

Back 20

The units of molar mass are gmol^-1

To calculate the molar mass we add up the

different mass numbers of the elements in the compound

For example the molar mass of carbon is 12gmol^-1

Front 21

How do we calculate the amount of substance (n)?

Back 21

Amount of substance = Mass (m)/ Molar mass (M)

(n)

This equation is essentially the one we use to find the moles of something, the mass in grams, or the MR

It basically looks like this:

Moles = mass (grams) / Mr (gmol^-1)

Front 22

What is the molecular formula?

Back 22

The number of atoms of each element in a

molecule

Front 23

What is the empirical formula of a compound?

Back 23

The simplest whole number ration of atoms of each element in a compound

Front 24

What are examples of the Empricial formula?

Back 24

The molecular formula of nitrogen dioxide is:
N2O4

But its empirical formula is:

NO2

We divide by 2, the smallest number out of 2 and 4, to find the simplest whole number ratio of 1:2

Front 25

What are hydrated salts?

Back 25

Solutions of salts and water that form a

crystalline solid

Front 26

What is the water of crystallisation?

Back 26

The water that is chemically bonded into a crystal structure

(Aka the water that makes a dry salt a hydrated salt)

Front 27

What is an anhydrous salt?

Back 27

A compound in which all water molecules are

removed

Front 28

How do we calculate the empirical formula from mass?

Back 28

We convert the mass they have given us into moles using the equation Moles = mass/ Molar mass

We then rewrite the moles we got into a ratio, to find the smallest whole number ratio we

divide by the smallest whole number

We then write the empirical formula using the ratio which tells us how many atoms of each

element we need

Front 29

How do we calculate the molecular formula of a compound?

Back 29

So first we convert the mass into moles using the equation: Moles = mass (grams) / Molar Mass (M)

Then we put these into a ratio and divide by the smallest whole number to figure out the

empirical formula

Then we write the relative mass of the

empirical formula by adding up the mass

numbers of the elements in the formula

In this question they would have given us the total relative molecular mass of a compound. We want to find how many of our empirical

formula fit into it so we divide the compound mass by the relative mass of our empirical

formula

We then multiply each element in our empirical formula by the answer we just got to find the molecular formula

Front 30

How do we calculate the number of water

molecules in a hydrated salt if we are given the total molar mass?

Back 30

Say we are given the question:

Ni(NO3)2 . xH2O, Calculate the value of x when the total molar mass is 290.7 gmol^-1

First we want to calculate the molar mass of Ni(NO3). To do this we just add up the mass numbers of the elements in the compound this = 183

Then we subtract them from the total molar mass of 290.7 which equals 107.7

We then divide 107.7 by the molecular mass of water, we do this to see how many water

molecules can fit into 108. When we do this we get 5.9 and then round to 6 so x =6

Front 31

When do we round up or multiply when we are calcualting the empirical formula of a compound?

Back 31

When we are trying to write the simplest whole number ratio for the empirical formula, sometimes when we divide by the smallest number we can get a decimal such as:

1: 3.92 , in this case we round 3.92 to 4 since its so close

But in the case we get 1:1.5 we can't round to 2 because its too far away, instead we multiply by 2 to get the simplest whole number ratio of 2:3

Front 32

What is the rule for rounding or multiplying when calculating the empirical formula?

Back 32

Round if VERY CLOSE to the whole number - no more than 0.1 away

When to multiply will be obvious:

Anything with 0.25 means we x4

Anything with 0.33 means we x3

Anything with 0.5 means we x2

Front 33

How do we calculate the number of atoms in a molecule?

Back 33

First we calculate the number of mols using the equation n=m/M

Then we do mols x avogadros constant

Front 34

How do we calculate the empirical formula if we are giving the percentage by mass?

Back 34

First we do the percentage by mass of each element divided by the mass number of each element

Then we divide the ratio by the smallest whole number ratio

Then we should get the simplest whole number ratio, if not we multiply to make them a whole number

Front 35

What is ionic bonding?

Back 35

The electrostatic attraction between psotitive and negative ions. Holds together positive ionss and negative ions in ionic compounds

Front 36

How do we show ionic bonding using a diagram?

Back 36

We do a Dot and cross diagram using square brackets

If we are given the formula and we want to show it and one of the elements we need 2 of, we can draw the square bracket for one and just draw a big 2 infront of it

Front 37

What are giant ionic compounds?

Back 37

Contains billions of billions of ions held in a giant ionic lattice

Front 38

Why are ionic compounds solid at room temp?

Back 38

There is insufficient energy to voercome the strong electrostatic forces of attraction between the oppositely charged ions in the giant ionic

lattice

This is also why they have high MP and BP

Front 39

What is solubility like in ionic compounds?

Back 39

Usually soluble in polar solvents, like water. Polar water molecules break down the lattice and

surround each ion in solution

In a compound made of ions with large charges, the ionic attraction may be too strong for water to be able to break down the lattic structure - the compound will not then be very soluble

Front 40

What is electrical conductivity like in ionic

compounds?

Back 40

In a solid state, an ionic compound does not

conduct electricity but once melted or dissolved in water, the ionic compound does conduct

electricity

This is because in a solid state the ions are fixed in position in the latice so they cant move to carry an electrical charge, this means they cant conduct electricity

In liquid or molten state they can conduct

electricity as the solid ionic lattic breaks down so the ions are now free to move

Front 41

What is covalent bonding?

Back 41

The strong electrostatic attraction between a pair of electrons and the nuclei of the bonded atoms

Front 42

What is the displayed formula?

Back 42

Shows the relative positioning of atoms and the bonds between them as lines

Paired electrons that are not shared are called lone pairs, these can also be added to displayed formulae

Front 43

What are multiple covalent bonds?

Back 43

A multiple covalent bond exist s when 2 atoms share more than one pair of electrons

Front 44

What are double and triple covalent bonds?

Back 44

The electrostatic attraction is between 2/3 shaired pairs of electrons and the nuclei of the bonding atoms

Front 45

What is a dative covlanet bond/ coordinate bond?

Back 45

A covalent bond which the shared pair of electrons has been supplied by one of the bonding atoms only

In a dative covalent bond the shared pair was originally a lone pair of electrons on one of the bonded atoms

Represented by an aroow in the displayed

formula

Front 46

What is metallic bonding?

Back 46

The strong electrostastic attraction between positive ions and delocalised electrons

Front 47

What is the structure like in metals?

Back 47

The positive ions are fixed in position,

maintaining the structure and shape of the metal

The delocalised electrons are mobile and are able to move throughjout the structure

Front 48

What is the electrical conducitivty like in metals?

Back 48

Can conduct electricity in solid and liquid states, when a voltage is applied across the metal the delocalised electrons can move to carry the charge throughout the structure

Front 49

What is the MP and BP like in metals?

Back 49

High temperature are needed to provide the large amount of energy needed to overcome the strong electrostatic attraction between the

positive ions and electrons

Front 50

What are the properties of Giant covalent

structures?

Back 50

High MP and Bp - high temps are needed to

provide the large quatnity of energy needed to break the strong covalent bonds

Insoluble in almost all solvents. The covalent bonds holding together the atoms in the lattice are far too strong to be broken by interaction with solvents

Cant conduct electricity aside from graphene and graphite