As Chemistry Unit 1 Aqa New Spec

Front 1

How are ions formed in TOF mass spec

Back 1

sample is vaporised and electron gun is fired at it so it knocks off an electron

Front 2

Why does the sample need to be ionised?

Back 2

so it can be accelerated by the electric field and because ions are needed to generate a current when they hit the detector

Front 3

First ionisation energy

Back 3

X(g) -----> X2+ (g) + e-

The energy needed to remove 1 electron from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Front 4

How do the electron configurations of chromium and copper deviate from the trend?

Back 4

They donate one electron from the 4s orbital to the 3d sub orbital.

Cr= 1s2 2s2 2p6 3p6 3d5 4s1

Cu= 1s2 2s2 2p6 3s2 3p6 3d10 4s1

Front 5

Chemical properties of groups 1 and 2 due to number of outer electron shells

Back 5

these are easily lost to form positive ions

Front 6

Factors affecting ionisation energy

Back 6

NUCLEAR CHARGE (more protons In nucleus, more positively charged nucleus so stronger attraction between protons and electrons)

DISTANCE FROM NUCLEUS (electron closer to the nucleus will be more strongly attracted to the nucleus than if its further away)

SHIELDING (as number of electrons between outer electrons and nucleus increases, outer electrons feel less attraction to nucleus)

Front 7

Define Second ionisation energy

Back 7

X+ (g) -----> X2+ (g) + e-

energy needed to remove an electron from each ion 1 mole of gaseous 1+ ions

Front 8

Ionisation energy trend across a period

Back 8

increase, because it gets harder to remove an outer electron as larger nucleus, more protons so increased nuclear charge so stronger nuclear attraction between the protons and electrons

Front 9

why does aluminium deviate from the trend in group 3

Back 9

its outer shell electron is in 3p rather than 3s so the 3p on average is further away from the nucleus

Front 10

why is there a drop between group 5 and 6

Back 10

it is due to electron repulsion. The shielding is identical in the phosphorus and sulfur atom. In phosphorus the electron is being removed from a singly occupied orbital but In sulfur electron is being removed from orbital containing two electrons.

Front 11

How to work out number of particles

Back 11

n x Avogadro's constant

Front 12

Ideal gas equation

Back 12

pV=nRT

where P= pa

V= m3

R= 8.31

t= k

n

Front 13

Acid reacts with an alkali to make salt and water

Back 13

H2SO4 + 2NaOH ----> Na2SO4 + 2H2O

Front 14

How to make a standardized solution

Back 14

work out how many moles of sodium hydroxide you need the work out how many grams needed.

place weighing boat on digital scales, weigh the required mass of solid needed.

weigh the weighing boat by minusing the overall weight from the mass.

add distilled water to beaker and add solid and stir till completely dissolved.

tip it into 250 cm3 volumetric flask using funnel and rinse beaker with distilled water and add that to flask too.

top flask with distilled water till reaches the meniscus line. then stop and put stopper on.

Front 15

Perform a titration

Back 15

use pipette to measure out set vol of solution you want to know concentration of. Put in flask and add drops of indicator In it. Fill burette with standard solution of acid. use funnel to pour acid into the burette. do it at eye level

Front 16

Calculate percentage yield

Back 16

actual yield/ theoretical yield x 100%

Front 17

Advantages of high atom economy

Back 17

company with high atom economy will make more efficient

Front 18

how to work out atom economy

Back 18

mass of desired product/ sum of molecular masses of all reactants x 100%

Front 19

Electron pair repulsion

Back 19

electrons are all negatively charged, so charge clouds repel each other until they're as far as apart as possible.

Front 20

Linear

Back 20

2 bonds 180 bond angle

Front 21

trigonal planar

Back 21

3 pairs 120 bond angle

Front 22

tetrahedral

Back 22

4 pairs 109.5 bond angle

Front 23

trigonal pyramidal

Back 23

120 and 90

Front 24

lone pair bond angle

Back 24

-2.5

Front 25

define Electronegativity

Back 25

ability of an nucleus to attract electrons in a covalent bond

Front 26

covalent bonds in diatomic gases are...

Back 26

non polar because the atoms have equal electronegativity's so the electrons are equally attracted to both nuclei

Front 27

the greater the difference in electronegativity

Back 27

the more polar the bond

Front 28

what is permanent dipole

Back 28

if charge is distributed unevenly over a whole molecule it will have one. in a substance made up of permanent dipoles , there will be weak electrostatic forces of attraction between delta positive and negative charges on neighbouring molecules.

Front 29

Hydrogen bonding

Back 29

NOF,

strongest intermolecular forces

Front 30

what is bond enthalpy

Back 30

energy needed to break a bond

Front 31

breaking bonds is

Back 31

endothermic as energy Is needed to break them

Front 32

making bonds are

Back 32

exothermic

Front 33

mean bond enthalpy

Back 33

average energy needed to break a certain type of bond, over a ranger of compounds

Front 34

Enthalpy change of combustion

Back 34

is the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions with all reactants and products

Front 35

Enthalpy change of formation

Back 35

when 1 mole of a compound is formed from its elements In their standard states under standard conditions

Front 36

Enthalpy change of reaction

Back 36

when a reaction occurs in the molar quantities shown in the chemical equation, under standard conditions with all reactant and products in their standard states

Front 37

What are calorimetry experiments

Back 37

experiments that measure the heat given out by reactions

Front 38

enthalpy experiment for reactions that take place in solution

Back 38

just put reactants in a container, put a thermometer in to measure the change. Use a polystyrene beaker so you don't lose or gain too much heat from the sides

Front 39

Calorimetry and combustion reactions

Back 39

To find enthalpy of combustion of a flammable liquid you burn it inside a calorimeter. As fuel burns it heats the water and you can work out the heat absorbed if you know the mass of water.

All heat given out by fuel would be absorbed by water so you can work out the enthalpy change of combustion

Front 40

Equation for enthalpy change

Back 40

Q=MCΔT

Front 41

Calculate the standard enthalpy of combustion

Back 41

1) calculate amount of heat lost( Q=MCΔT)

2)calculate the number of moles of fuel that caused this enthalpy change (n=mass/mr)

3)calculate the standard enthalpy change of combustion using equation

(Standard enthalpy of combustion= q/n)

Front 42

Enthalpy change of neutralisation

Back 42

when one mole of water is formed by the reaction of an acid and an alkali

Front 43

Find enthalpy change of neutralisation

Back 43

add known vol of acid to insulated container, measure temp, add known vol of alkali and record temp rise. Stir solution so evenly heated

Front 44

experimental problems with all calorimetry

Back 44

some heat will be absorbed by the container rather than water

some heat always lost by surroundings

Front 45

experimental problems with flammable liquid calorimetry

Back 45

some combustion may be incomplete

some flammable liquid may escape by evaporation

Front 46

What is Hesse's law?

Back 46

the total enthalpy change for a reaction is independent of the route taken

Front 47

route 1 and route 2 for hesses law

Front 48

Formation cycles

Front 49

combustion cycle

Front 50

What is the collision theory?

Back 50

a reaction wont take place between two particles unless they collide in the right direction with at least a certain amount of minimum kinetic energy

Front 51

Activation energy

Back 51

minimum amount of kinetic energy particles need to react

Front 52

What does the peak in the Maxwell Boltzmann distribution represent?

Back 52

the most likely energy of any single molecule

Front 53

why does the curve start at (0,0) for Maxwell boltzmann

Back 53

because no molecules have zero energy

Front 54

The right of the peak of the Maxwell Boltzmann distribution represents

Back 54

the mean average of all the molecules

Front 55

the area under the Maxwell Boltzmann distribution curve is

Back 55

equal to the total number of molecules

Front 56

Effect of temperature on reaction rate

Back 56

the molecules on average have more kinetic energy and will move faster. So more molecules will have at least the activation energy and be able to react.

Front 57

how does Increase in temperature change the shape of the Maxwell Boltzmann distribution

Back 57

it pushes it over to the right

Front 58

Effect on concentration on reaction rate

Back 58

the particles will on average be closer together so more frequent collisions

Front 59

How do catalysts increase rate of reaction

Back 59

by providing an alternative reaction pathway with a lower activation energy. They don't get used up

Front 60

A catalyst lowers the activation energy so...

Back 60

there a more particles with enough energy to react when they collide.

Front 61

Calculating reaction rate=

Back 61

amount of reactant used or product formed/time

Front 62

Measure rate of reaction experiment (precipitate formation)

Back 62

when you mix sodium thiosulfate solution to colourless hcl it forms a yellow precip of sulphur.

Put conical flask on white tile with black X mark on it.

add fixed vols of reactions solutions to flask and start stop watch.

as precip forms, mark will disappear, when it completely disappears, stop the timer and record the time. Repeat this for different temperatures

Front 63

Rate of reaction experiment (Change in mass)

Back 63

work for reaction between HCL and calcium carbonate where CO2 is given off. place flask on weighing scales. when reaction starts, start timer, read off at regular intervals, record mass and time in table. Reaction finishes when the mass stops decreasing.

Best to carry this out in fume cupboard

Front 64

Rate of reaction experiment (gas volume)

Back 64

measure gas given off by collecting it in a gas syringe and recording how much you've got at regular intervals.

work for reaction between magnesium and acid where H2 given off.

Start timer, read off gas syringe at regular time intervals . Reaction stops when gas vol stops increasing. This method is accurate, no gas escapes but do it in fume cupboard just incase. work out how much gas you expect as vigorous reactions can blow the top off the syringe.

You can repeat reaction at different temps

Front 65

Define Dynamic Equilibrium

Back 65

when the forwards reaction is the same rate of the backwards reaction

Front 66

What is le chateliers principle?

Back 66

if a reaction at equilibrium is subjected to a change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change

Front 67

If the position of equilibrium moves left

Back 67

the backwards reaction is faster than the forwards reaction, so you'll get more reactants

Front 68

if the position of equilibrium moves to the right

Back 68

the forwards reaction is faster than the backwards reaction, so you'll get more products

Front 69

Using le chateliers principle, define changing concentration

Back 69

if you increase conc of reactants, the equilibrium will try to get rid of the extra reactant by making more products so the equilibrium shifted to the right.

Front 70

If you increase the concentration of the product..

Back 70

equilibrium tried to remove the extra product so will make the reverse reaction move faster and equilibrium shifts to the left

Front 71

changing pressure only affects equilibrium..

Back 71

involving gas

Front 72

increasing pressure shifts equilibrium

Back 72

to the side with fewer molecules. This reduces pressure.

Decreasing pressure shifts it to the side with more molecules

Front 73

increasing the temperature shifts equilibrium

Back 73

to the endothermic direction to absorb the heat,

Front 74

decreasing the temperature shifts equilibrium

Back 74

to the exothermic side to replace the heat

Front 75

if the forwards reaction is endothermic then the backwards reaction will be...

Back 75

exothermic

Front 76

When Cu(h2o) reacts with HCL...

Back 76

a copper chloride complex forms.

Front 77

in a reaction with Cu(H2O) and CuCl4

Back 77

you can track the position of equilibrium by noting what colour the solution is as CuH2O is a light blue colour and CuCl4 is a green yellow.

If the solution is blue then the position of equilibrium must lie on the left and there will be more reactants than products. If the solution is greeny yellow, the equilibrium must lie to the right and there will be more products

Front 78

changing the concentration for Cu(H2O)6...

Back 78

you'll see it is a light blue colour. If you slowly add HCL solution colour will turn from light blue to bluey greeny. the more HCL added the more CuCl4 complex forms. This is because as you add more hcl conc of CL- increases so equilibrium moves to right.

Front 79

Changing the temperature of sample containing Cu(H2O6) and CuCl4

Back 79

the forward reaction is endothermic so if you heat the sample containing that the equilibrium will move to the right to absorb the extra heat.

Front 80

compromise conditions in industry

Back 80

for reaction with ethanol which is reversible; conditions are:

PRESSURE= 60-70 atm

TEMPERATURE= 300c

PHOSPHORIC ACID CATALYST

Front 81

Methanol conditions in industry

Back 81

50-100 atm

250c

CATALYST of; copper, zinc oxide, aluminum oxide

Front 82

The equilibrium constant

Front 83

second picture of equilibrium constant

Front 84

changing the temperature of the equilibrium constant

Back 84

increase temp, equilibrium shifts to endothermic direction, decreasing temp removes heat energy, so shifts to exothermic side

Front 85

changing conc of equilibrium constant

Back 85

value of equilibrium constant is fixed at given temperature so if conc of one thing changes, conc of others must change to keep the value of Kc the same

Front 86

Adding a catalyst to equilibrium constant

Back 86

no effect as catalyst increases both reactions

Front 87

What are redox reactions?

Back 87

reduction and oxidation happening simultaneously in a reaction

Front 88

oxidation is

Back 88

loss of electrons

Front 89

reduction is

Back 89

gaining electrons

Front 90

An oxidising agent

Back 90

accepts electrons and gets reduced

Front 91

reducing agent

Back 91

donates electrons and gets oxidized

Front 92

oxidation state

Back 92

tells you the total number of electrons it has donated or accepted

Front 93

uncombined elements have an oxidation state of

Back 93

0

Front 94

elements just bonded to identical atoms also have an oxidation state of

Back 94

0

Front 95

the most electronegative element has a

Back 95

negative oxidation stare equal to its ionic charge

Front 96

ionic half equations show

Back 96

oxidation or reduction

Front 97

redox equations

Front 98

in redox reactions, oxidation and reduction happens

Back 98

simultaneously

Front 99

when oxidation and reduction equations get more complicated, you need to balance the sides up with

Back 99

H2O and H+ ions