Difficult/memory

Question 1

Describe electron pair repulsion theory

Answer 1

Each pair of electrons around an atom will repel all other electrons.
The pairs will therefore take up position as far apart as possible to minimise repulsion.

Question 2

Shape of molecule: two pairs of electrons

Answer 2

Linear. 180°

Question 3

Shape of molecule: three pairs of electrons

Answer 3

Trigonal planar. 120°

Question 4

Shape of molecule: four pairs of electrons

Answer 4

Tetrahedron. 109.5°

Question 5

Shape of molecule: five pairs of electrons

Answer 5

Trigonal bipyramid. 90° (same plane) 120° on different.

Question 6

Shape of molecule: six pairs of electrons

Answer 6

Octahedral. 90°

Question 7

What is the effect of a lone pair of electrons.

Answer 7

Reduces the bond angle by 2.5°

Question 8

What is the order of electron pair repulsion.

Answer 8

bp-bp< bp lp< lp lp

Question 9

Name the classification rule for the period table (s,p,d)

Answer 9

S block- highest energy electrons are in the s- orbitals (eg. Li 1s2, 2s1)

P block- highest energy electrons are in the p- orbitals (eg. C 1s2, 2s2, 2p2)

D block- highest energy electrons are in the d- orbitals (eg. Fe 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6)

Question 10

Relative atomic msss

Answer 10

average mass of an atom relative to 1/12 of 1 atom of carbon-12.

Question 11

Why is a mass spec kept under a vacuum

Answer 11

To prevent the ions that are produced colliding with molecules from the air.

Question 12

Describe electrospray ionisation

Answer 12

The sample is dissolved in a volatile solvent
Then forced through a fine hollow needle which is connected to a + terminal.
Produces tiny + charged droplets that have gained a proton.
Solvent evaporates.

Question 13

Describe electron impact ionisation

Answer 13

Sample is vaporised
High energy electrons fired from an electron gun.
This knocks off one electron from each ion forming +1 ions.
X(g) + e- ——-> X+(g) + 2e-

Question 14

What happens in a mass spec

Answer 14

Ionisation
Acceleration- + ions are attracted to - charged plate and accelerate towards it. Lighter ions travel faster.
Ion drift- ions pass through hole in - charged plate, called flight tube to the detector
Detection- flight times of each ion is recorded, + ions pick up electrons from the detector causing currently to flow

Question 15

What is the electron arrangement for Cr

Answer 15

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5

Question 16

What is the electron arrangement for Cu

Answer 16

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10

Question 17

Define first ionisation energy

Answer 17

energy required to remove one mole of electrons from an atom in a gaseous state.

Question 18

What is Avogadro constant

Answer 18

The number of atoms in 12g of carbon-12.

6.022x10^23. A mole has 6.022x10^23

Question 19

Ideal gas equation

Answer 19

PV=nRT.

Pa x m3 = n x JK-1mol-1 x K

Question 20

What is 0 K in °

Answer 20

-273

Question 21

What is an empirical formula

Answer 21

The formula that represents the simplest whole number ratio.

Question 22

What is a molecular formula

Answer 22

The actual number of atoms of each element in a molecule.

Question 23

What are the forces holding ionic compounds.

Answer 23

electrostatic forces

Question 24

Describe an ionic structure

Answer 24

Giant ionic lattice

Question 25

Does ionic bonding conduct.

Answer 25

Conducts when molten or dissolved.

Question 26

Describe ionic compounds melting and boiling points

Answer 26

High m and b points due to strong electrostatic forces

Question 27

What is a co-ordinate bond/ dative covalent bond

Answer 27

When an atom in a covalent bond donates a pair of electrons, rather than one electron.

Question 28

What are the bonds in a covalent molecule

Answer 28

covalent bonds

Question 29

Describe the structure of a metallic compound.

Answer 29

Positive ions in a sea of delocalised electrons. Giant structure.

Question 30

Define electronegativity

Answer 30

Electronegativity is the power of an atom to attract the electron density in a covalent bond towards itself.

Question 31

Describe the trends in electronegativity

Answer 31

Increases going up a group: there is less shielding. | Increases going across a period: nuclear charge increases without extra shielding so atoms get smaller.

Question 32

Name 3 intermolecular forces in order of strength

Answer 32

Van der Waals, dipole dipole forces, hydrogen bonds.

Question 33

What are dipole dipole forces

Answer 33

Forces that act between molecules that have permanent diapoles

Question 34

What are Van der Waal forces

Answer 34

Forces that act between all molecules. They are forces that act between an instantaneous diapole and an induced dipole.

Question 35

What makes Van der Waal forces larger

Answer 35

More electrons= larger force. As the diapoles are caused by moving electron clouds, the more elctrons, the stronger the diapole.

Question 36

What is enthalpy change

Answer 36

heat change at constant pressure

Question 37

Standard molar enthalpy of formation

Answer 37

enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, all reactants and products being in their standard states.

Question 38

standard molar enthalpy of combustion

Answer 38

enthalpy change when one mole of substance is burned in oxygen under standard conditions, all reactants and products being in their standard states.

Question 39

enthalpy change equation

Answer 39

q=mCAT (mass in grams)

Question 40

bond disassociation enthalpy

Answer 40

enthalpy change required to break a covalent bond, with all species in a gaseous state.

Question 41

Name the 5 things that affect a rate of reaction.

Answer 41

``` Temperature Concentration of a solution Pressure of a gas SA of solid reactants Catalyst ```

Question 42

Define activation energy

Answer 42

The minimum energy that a particle needs in order to react

Question 43

What effect does temperature have on a Maxwell Boltzmann distribution graph.

Answer 43

Flattens the curve and pushes it to the right, with more particles over Ea. The total area under the curve is the same. Average and most probable energy increases.

Question 44

What is a catalyst

Answer 44

Catalysts are substances that increase the rate of reaction (by offering an alternate reaction pathway with a lower activation) without being chemically changed themselves at the end of the reaction.

Question 45

Describe a catalytic converter

Answer 45

a honeycomb, made of a ceramic material, coated with platinum and rhodium metals (the catalysts). honeycomb to increase surface area.

Question 46

catalytic converters reactions

Answer 46

carbon monoxide +nitrogen oxides——> nitrogen and carbon dioxide hydrocarbons + nitrogen oxides——> nitrogen +carbon dioxide + water

Question 47

describe the steps of the reaction that take place on the catalytic converter

Answer 47

1. adsorption - gases form weak bonds with metals atoms of the catalyst. The gases react on the surface. 2. desorption- the products break away from the metal atoms.

Question 48

Define dynamic equilibrium

Answer 48

When concentration of reactants and products remain constant because the forward and backward reaction are moving at the same rate.

Question 49

State Le Châtelier’s principle

Answer 49

If a system is distributed, the equilibrium moves in the direction that tends to reduce the disturbance.

Question 50

Define an isomer

Answer 50

molecules that have the same molecular formula but whose atoms are arranged differently.

Question 51

Name 3 structural isomers

Answer 51

Positional, functional, chain

Question 52

Describe positional isomerism

Answer 52

isomers where the same functional groups are attached to the main chain at different points.

Question 53

Describe functional isomerism

Answer 53

isomers where the functional group is different

Question 54

Describe chain isomerism

Answer 54

isomers where the hydrocarbon chains are branched differently.

Question 55

Name a type of stereoisomerism/geometric

Answer 55

E-Z isomerism

Question 56

Describe E-Z isomerism

Answer 56

Arrangement of bonds in space, around a double bond as there is no rotation around a double bond.

Question 57

Describe thermal cracking

Answer 57

Heating alkanes to a high temperature under high pressure. Produces alkanes and alkenes.

Question 58

Describe catalytic cracking

Answer 58

Takes place at lower temperatures and pressure. Uses zeolite catalyst. Produces branched alkanes, cycloalkanes and aromatic compounds.

Question 59

What is incomplete combustion

Answer 59

When a substance burns in a limited supply of oxygen so CO is formed.

Question 60

What are the products when an alkane burns

Answer 60

carbon dioxide and water

Question 61

Why are CFC’s destroying the ozone

Answer 61

When CFC’s are exposed to UV light they can form chlorine free radicals which reacts with the ozone and breaks it down into O2.

Question 62

Show the equations for the breakdown of ozone

Answer 62

C. +O3 —-> ClO. + O2 ClO. +O3 ———> 2O2 + Cl. Overall: 2O3—-> 3O2

Question 63

Describe and explain the trend in atomic radius across period three

Answer 63

Atomic radii decrease due to increased nuclear attraction with no increased shielding ng.

Question 64

Describe and explain the trend in first ionisation energy.

Answer 64

Increases across a period as it requires more energy to get rid of an electron as the nuclear attraction also increases across a period.

Question 65

Describe and explain the trend in melting points across period 3.

Answer 65

Giant structures (left) have high melting points whereas molecular structures (right) have lower boiling points. Molecular structures mp depends on how packed the electrons are (Van der Waal forces). For this reason S8>P4>Cl2

Question 66

Group 2 reaction with water

Answer 66

M(s) + 2H2O (l) —-> M(OH)2 + H2 (g)

Question 67

Magnesiums reaction with steam

Answer 67

Mg (s) +H2O (g) ——> MgO (s) +H2 (g)

Question 68

Describe the trend in solubility of group 2 hydroxides.

Answer 68

As you go down the group they become more soluble.

Question 69

Describe the trend in solubility of group 2 sulfates

Answer 69

As you go down the group they become less soluable.

Question 70

Name a use of barium sulfate

Answer 70

When ingested outlines gut so it can be seen in an xray

Question 71

Describe the trend in oxidising ability in the halogens

Answer 71

The oxidising ability of the halogens increases going up a group.

Question 72

Reaction of NaCl and conc. sulphuric acid

Answer 72

NaCl (s) + H2SO4 (l) ——> NaHSO4 (s) + HCl (g)

Question 73

Reaction of NaBr and conc. sulphuric acid

Answer 73

Two Reactions NaBr (s) + H2SO4 (l) ——> NaHSO4 (s) + HBr (g) But then HBr reacts with H2SO4 to produce sulfur dioxide water and bromine 2H+ +2Br + H2SO4 (l) ——> SO2 (g) + H2O (l) + Br2 (l)

Question 74

Reaction of sodium iodide

Answer 74

Nal (s) + H2SO4 (l) ——> NaHSO4 (s) + HI (g) But then the HI reacts with the acid to produce hydrogen sulfide water and iodine. 8H+ +8I- +H2SO4 (l)—-> H2S (g) + 4H2O (l) + 4I2 (s)