As Chemistry Unit 1

Front 1

Protons

Back 1

Relative mass is 1 and has a charge of +1

Front 2

Neutrons

Back 2

Relative mass is 1 and has a charge of 0

Front 3

Electrons

Back 3

Relative mass is 1 over 2000 and has a charge of -1.

Front 4

Atomic (proton) number

Back 4

Is the number of protons in the nucleus, all atoms of the same element have the same proton number.

Front 5

Isotopes

Back 5

Isotopes are atoms with the same number of protons but different numbers of neutrons. Electrons decide the chemical properties of an element. Isotopes have the same electronic arrangement, so they have the same chemical properties.

Front 6

1st Ionisation energy

Back 6

The first ionisation energy is the energy required to form 1 mole of positive gaseous ion from 1 mole of gaseous atoms.

Front 7

2nd Ionisation energy

Back 7

The second ionisation energy is the energy required to from 1 mole of di-positive gaseous ion from 1 mole of positive gaseous ions

Front 8

Factors affecting ionisation energy:

Back 8

•Nuclear charge

•Distance from nucleus (atomic radius)

•Shielding

Front 9

Nuclear charge

Back 9

The more protons in the nucleus, the more positively charged the nucleus, so the attraction for the electrons is greater.

Front 10

Distance from nucleus (atomic radius)

Back 10

The closer the electron to the nucleus the stronger the charge/attraction. The closer the nucleus the electron is the smaller the atomic radius.

Front 11

Shielding

Back 11

When the number of electrons between the outer electron and the nucleus increase, the outer electrons feel less attraction towards the nucleus, this is due to shielding.

Front 12

Trends of 1st Ionisation energies:

Back 12

The ionisation energy down a group decrease because as you go down a group the shielding increases because the number of shells and electrons between the outer electron and nucleus increases. The ionisation energy across a period generally increase because the proton number in the nucleus is increasing so there is a strong attraction for electrons which are in the same shell. Across a period the ionisation energy will go up and down, and ionisation energy of an element will increase.

Front 13

Relative atomic mass:

Back 13

Relative atomic mass is the average mass of an atom based on the c-12 carbon atom with a value of 12.

Front 14

Relative isotopic mass

Back 14

Relative isotopic mass is the average mass of an isotope based on the c-12 carbon atom with a value of 12.

Front 15

Relative molecular mass

Back 15

Relative molecular mass is the average mass of a molecule or formula unit based on the c-12 carbon atom with a value of 12.

Front 16

Mass Spectrometer

Back 16

The mass spectrometer can be used to find out the relative atomic mass, relative molecular mass, molecular structure etc. It has 5 stages. Vaporisation, this is where the sample is turned into a gas using an electric heater; Ionisation, the particles are bombarded with high energy electrons, removing an outer electron making them positive ions; Acceleration, an electric field is used to accelerate positive ion; Deflection, A magnetic field is used to deflect positive ions, the lighter ions are deflected more and finally detection, the magnetic field is slowly increased, so different ions can be detected and a mass spectrometer produced.

Front 17

Moles

Back 17

•Number of moles = number of particles ÷ Avogadro’s constant (6 times 10 to the power of 23).

•Number of moles = mass of a substance ÷ molar mass.

•Number of moles = concentration times volume in cm cubed ÷ 1000.

•Number of moles = volume in decimetres cubed ÷ 24 or volume in centimetres cubed ÷ 24000

Front 18

Empirical formula:

Back 18

Empirical formula is the smallest whole number ratio of atoms in a molecule.

Front 19

Molecular formula:

Back 19

Molecular formula is the actual number of atoms in a molecule.

Front 20

Theoretical yield:

Back 20

The theoretical yield is the mass of the products that should have been formed. Theoretical yield is number of moles of the product times molar mass of the product.

Front 21

Percentage yield:

Back 21

Percentage yield of a product is never 100% because the actual yield is never the same as the theoretical yield because some product may be lost. Percentage yield is actual yield ÷ theoretical yield times 100.

Front 22

Titrations:

Back 22

Allows you to work out how much acid is needed to neutralise an alkali. Methyl orange turns yellow to red when adding acid to an alkali. Phenolphthalein, turns from red/pink to colourless when adding an acid to an alkali.

Front 23

Percentage error:

Back 23

work out the percentage error in titration it is error ÷ reading times 100.

Front 24

Atom economy:

Back 24

Tells you how wasteful a product is, atom economy is a measure of the proportion on reactant atoms that becomes part of the desired product. To work out atom economy percentage is the molecular formula of the desired product ÷ the sum of molecular masses of all products times 100. Addition reactions have 100% atom economy; substitution reactions have a lower atom economy.

Front 25

Ionic bonding:

Back 25

Ionic bonding is the bonding between cat ions and an ions. The electrostatic attraction that holds the positive and negative ions together is very strong. Ionic compounds form giant ionic lattice structures. A lattice is a regular structure and it is giant because it is the same repeat unit over and over again. Ionic compounds conduct electricity when molten or dissolved, ionic compounds have high melting points and dissolve in water.

Front 26

Ionic radius:

Back 26

Ionic radius is the size of an ion. The ionic radius increases as you go down a group. This is because the groups have the same charge, so the ionic radius increases as the atomic number increases; this is because electron shells are being added.

Front 27

Isoelectronic ions:

Back 27

Isoelectronic ions are ions of different atoms with the same number of electrons, the ionic radius of a set of ions decrease as the atomic number increases.

Front 28

Covalent bonds:

Back 28

A covalent bond is the sharing of electrons between two atoms this happens when two atoms approaches each other and their electron clouds overlap and electron density is greatest between the nuclei.

*Covalent bonds can be sigma bonds. An overlap of s-orbitals giving the highest possible electron density or covalent bonds can be pi bonds, and overlap of 2 electrons in the p orbitals. Pi bonds are weaker than sigma bonds and are more reactive.

Front 29

Dative covalent bonds:

Back 29

A dative covalent bond is a covalent bond but both the shared electrons come from just one of the atoms. A double bond comes from 2 shared electrons, and a triple bond results from 3 shared electrons.

Front 30

Giant molecular structure:

Back 30

Giant molecular structures have a large network of covalent bonds. Giant molecular structures are diamonds, graphite and silicon 4 oxide. This is because carbon and silicon can form four strong covalent bonds.

Front 31

Diamonds:

Back 31

Diamonds is the hardest known substance, it is made up of carbon atoms, and each carbon atom is covalently bonded to four other carbons. They arrange themselves in a tetrahedral shape. Diamonds are good thermal conductors because vibrations travel easily through the stiff lattice. It has a very high melting point, it can’t conduct electricity because all the outer electrons are held in localised bonds and it doesn’t dissolve in any solvent.

Front 32

Graphite:

Back 32

Graphite is an allotrope, (different forms of the same element in the same state) of carbon. Graphite’s structure means it has different properties from diamond. Weak bonds between the layers in graphite are easily broken so layers can slide over each other; delocalised electrons are free to move along the layers carrying an electric current around; layers held together by weak Van der Waals forces; graphite is less dense because the layers are far apart; because of the strong covalent bonds, graphite has a high melting point and it is insoluble in any solvent.

Front 33

Metallic bonding:

Back 33

A metal is made up of an array of cations and delocalised electrons. The electrostatic force between the oppositely charged particles is the metallic bond. The more delocalised electrons the stronger the bond so the higher the melting point, no bonds holding specific ions together so metals are malleable and ductile, delocalised electrons can carry a current and metals are insoluble, except in liquid metals.

Front 34

Periodic trends:

Back 34

Atomic radius decreases across a period, as the protons increase, the positive charge of the nucleus increases meaning the electrons are pulled closer to the nucleus, making the atomic radius smaller, electronegativity increases across a period, ionisation energies generally increase across a period.

Front 35

Homologus series:

Back 35

A group of compounds can be represented by the same general formula is the homologus series. The general formula can be used to work out the molecular formula. Each successive members of a homologus series differs by a CH2 group.

Front 36

Alkanes and Alkenes

Back 36

Alkanes = CnH2n+2. Alkenes = CnH2n and Alcohols = CnH2n+1O H
•Meth is 1 carbon
•Eth is 2 carbons
•Prop is 3 carbons,
•But is 4 carbons
•Pent is 5 carbons
•Hex is 6 carbons
•Hept is 7 carbons
•Oct is 8 carbons
•Non is 9 carbons
•Dec is 10 carbons.

Front 37

Chain Isomers:

Back 37

Chain isomers have a different arrangement of the carbon skeleton, some are straight and some are branched.

Front 38

Positional isomers:

Back 38

Positional isomers have the same skeleton and same functional group, the difference is that the group is attached to a different carbon atom.

Front 39

Functional group isomers:

Back 39

Functional group isomers have the same atoms arranged into different functional groups.

Front 40

Alkanes:

Back 40

Alkanes are saturated hydrocarbons; every carbon has 4 single bonds with other atoms. It is impossible for the carbon to make more than 4 bonds.

*Alkanes have a tetrahedral shape around each carbon with a bond angle of 109.5.

*Alkane’s burn completely in oxygen, if you burn oxygen and alkanes, carbon dioxide and water is produced. This is a combustion reaction and is exothermic. Combustion happens in gases so liquid alkanes would be vaporised into gases first.

Front 41

Fractional distillation:

Back 41

Crude oil is vaporised at 350 degrees Celsius. The largest hydrocarbons won’t vaporise as their boiling points are too high. As the crude oil vapour goes up the fractioning column it gets cooler and because of the different chain lengths, each fraction condenses at different temperatures. Fuel, wax, grease and are at the bottom and petrol and gases at the top.

Front 42

Cracked:

Back 42

Heaving fractions from the column are cracked to make them smaller. Cracking involves breaking ling chains into smaller hydrocarbons by breaking the C-C bonds.

Front 43

Thermal cracking:

Back 43

Thermal cracking takes place at high temperatures (1000 degrees) and at high pressures or 70atmospheres. It produces a lot of alkanes which is used to make heaps of valuable products such as polymers. E.g.: Poly (ethene) which is made from ethene.

Front 44

Reforming:

Back 44

Converting alkenes into arenes is called reforming and uses a catalyst such as platinum on aluminium oxide.

Front 45

Heterolytic fission:

Back 45

In heterolytic fission two different substances are formed – positive charged cat ions and negatively charged an ions.

Front 46

Homolytic fission:

Back 46

Homolytic fission is the formation of 2 free radicals. Free radicals are particles that have an unpaired electron making them very reactive.

Front 47

Free radical substitution reaction:

Back 47

Halogens react with alkanes in photochemical reactions, which are started by UV lights. A hydrogen atom is substituted by Cl2 or Br2.

*Free radical substitution reaction mechanism has three stages:

•Initiation reaction: Free radicals are produced under UV light, this is homolytic fission.

•Propagation reaction: In propagation free radicals are used up and produce one free radical and a molecule.

•Termination reaction: Two free radicals join together to make a stable molecule.

Front 48

Alkenes:

Back 48

Alkenes are unsaturated hydrocarbons. Alkenes have at least one C double bond C bond. They can make extra bonds with atoms in addition reactions.

*Alkenes are oxidised by acidified potassium manganate 7.

*Alkenes are more reactive than alkanes because there are two pairs of electrons in the C double bond C bond, meaning it has a really high electron density.

Front 49

Electrophilic addition reactions:

Back 49

An electrophilic addition reaction happens to alkenes. In Electrophilic addition the double bond opens up and the other atoms are attached to each of its carbons. The double bonds have plenty of electrons that are attacked by an electrophile. The double bond is also nucleophilic, it’s attracted to places without enough electrons.

Front 50

Electrophiles

Back 50

Electrophiles are electron pair acceptors. They are positively charged ions such as H+.

Front 51

Test for Alkenes

Back 51

Bromine reacts with alkenes by electrophilic addition. Bromine water which is orange when it reacts with alkenes it decolourises. Also a test for C double bond C bonds.

Front 52

E Z isomerism:

Back 52

E Z isomerism is a form of stereoisomerism.

Front 53

Stereoisomerism:

Back 53

Stereoisomerism has the same structural formula but different arrangements, because of lack of rotation around the double bond, alkenes can have stereoisomerism. Alkanes DO NOT!!

*If two double bonded carbon atoms have different atoms or groups attached to them, you get an E or Z isomer.

Front 54

E isomers:

Back 54

E isomers are the same group or atom across the double bond.

Front 55

Z isomers:

Back 55

Z isomers are the same group on the same side of the double bond.

Front 56

Cis:

Back 56

Cis is the same as Z. The groups are on the same side of the double bond.

Front 57

Trans:

Back 57

Trans is the same as E. The groups are on opposite sides of the c double bond c bond.

*If all four of the groups are different, then you base the E Z on the highest priority. If the higher priority is on the same side it is a Z, if it is on opposite sides it’s an E isomer.

Front 58

Polymers:

Back 58

Polymers are double bonds in alkenes can open up and join together to make long chains.

Front 59

Monomers:

Back 59

Small individual alkenes are monomers.

Front 60

Addition polymerisation:

Back 60

Addition polymerisation is an alkene monomer becoming a polymer. For example poly (ethene) is made by the addition polymerisation of ethene.

Front 61

Polymers:

Back 61

Polymers can be used in Teflon pans, plastic windows, plastic crates, bags, bottles etc. however it is very un-reactive which makes it hard to dispose of. They are non bio-degradable.

Front 62

Enthalpy:

Back 62

When a chemical reaction occurs some bonds are broken and some are made by changing the energy.

*Enthalpy change (delta H) is the heat energy transferred in a reaction at a constant pressure. The units of enthalpy change are kJ mol minus 1.

Front 63

Exothermic

Back 63

Exothermic reactions give energy out. The enthalpy change is negative.

Front 64

Endothermic:

Back 64

Endothermic reactions energy is absorbed from the surroundings. The enthalpy change is positive.

Front 65

Standard enthalpy change of reaction, delta H r:

Back 65

Is the enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation, under standard conditions in their standard state.

Front 66

Standard enthalpy change of formation, delta H f:

Back 66

: Is the enthalpy change when 1 mole of a compound is formed from its elements in their standard state, under standard conditions. E.g. Carbon (gas) + Oxygen (gas) = Carbon dioxide (gas)

Front 67

Standard enthalpy change of combustion, delta H c:

Back 67

Is the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions.

Front 68

Standard enthalpy change of neutralisation, delta H neut:

Back 68

Is the enthalpy change when 1 mole of water is formed the neutralisation of hydrogen ions and hydroxide ions under standard conditions.

Front 69

Standard enthalpy change of atomisation, delta H at:

Back 69

Is the enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state.

Front 70

Standard Conditions

Back 70

Standard conditions are at 1 atmosphere pressure and 25 degrees temperature

Front 71

Hess’ Law:

Back 71

Hess’ law is that the total enthalpy change of a reaction is always the same, no matter which route is taken.