Aqa As Chemistry Paper 1

Front 1

How are atoms ionised in electrospray ionisation?

Back 1

The sampleis dissolved in a volatile solvent and forced through a hypodermic needleattached to a positive terminal of a high voltage supply. This produces a finemist of positive ions which has lot electrons to the power supply. The solventevaporates from the droplets into the vacuum until they are travelling assingle ions.

Front 2

How are atoms ionised in electron impact?

Back 2

A gaseoussample is put into the ionisation chamber where a hot filament (electron gun)emits high speed electrons. These knock off electrons from the sample whichform positively charged ions.

Front 3

How are ions detected in mass spectrometry?

Back 3

The ions hita negatively charged plate. The positive ions gain an electron from thedetector causing a current to flow. The flight times are recorded. The size ofthe current is proportional to the abundance of the species and gives a measureof the number of ions hitting the plate.

Front 4

Which method of ionisation is used for bigger molecules such as proteins?

Back 4

Electrospray ionisation

Front 5

Define ionisation energy

Back 5

The enrgy required to remove one mole of electrons from a mole of atoms in the gaseous state.

Front 6

What's the trend in IE across a period?

Why?

Back 6

Increases

Nuclear charge increases, atomic radius decreases. Electrons have stronger attraction to nucleus.

Front 7

What happens from group 2-3 when looking at ionisation energies?

Back 7

IE decreases, as electron enters 'd' orbit- which is further from the nucleus.

Front 8

What happens from group 5-6 when looking at ionisation energies?

Back 8

IE decreases as there will be a paired electron in orbital, paired electrons repel each other so are easier to remove.

Front 9

What is the trend in IE down a group?

Why?

Back 9

Decrease in IE.

Outer electron moves to an a orbit further from the nucleus

Front 10

Define Empirical formula

Back 10

The formula which represents the simplest whole number ratio of the atoms of each element present in the compound.

Front 11

What's the trend in electronegativity down a group?

Back 11

Decreases

Less shielding by electrons in inner shells

Front 12

Trend in electronegativity across a period?

Back 12

Increases

Nuclear charge increases but inner main levels remains the same and atom becomes smaller.

Front 13

2 Bond pairs shape + Angle?

Back 13

Linear

180

Front 14

3 Bond pairs

Shape and angle?

Back 14

Trigonal planar.

120

Front 15

4 Bond pairs

Shape and Angle

Back 15

Tetrahedral

109.5

Front 16

5 Bond pairs

Shape + Angle?

Back 16

Trigonal Planar

120

90

Front 17

6 Bond pairs

Shape + Angle?

Back 17

90

Front 18

Define Enthalpy change.

Back 18

The heat transferred in a chemical reaction at constant temperature.

Front 19

Standard Enthalpy of Formation

Back 19

The enthalpy change when one mole of substance isformed from its constituent elements under standard conditions, all reactantsand products being in their standard state.

Front 20

Standard Enthalpy of Combustion

Back 20

The enthalpy change when one mole of substance iscompletely burnt oxygen under standard conditions, all reactants and productsbeing in their standard states.

Front 21

Hess’s Law?

Back 21

Theenthalpy change for a chemical reaction is the same, whatever route is takenfrom reactants to products.

Front 22

Mean bond enthalpy

Back 22

The average energy required to break a bond

Front 23

LeChatelier’s principle

Back 23

If a reaction is subjected to a change inconcentration, temperature or pressure, the position of equilibrium will moveto oppose the change.

Front 24

Oxidation

Back 24

Loss of electrons

Front 25

Reduction

Back 25

Gain of electrons

Front 26

Oxidising agent

Back 26

Accepts electrons

Front 27

Reducing agent

Back 27

Electron donor

Front 28

Trend in atomic radius across a period?

Why?

Back 28

Decreases.

As you move across, the more protons the element has.This means a stronger nuclear charge to pull electrons closer. There are noadditional electron shells to provide shielding so the size of the atomdecreases.�

Front 29

Trend in atomic radii down a group?

Why?

Back 29

Increase.

The atoms of each element have one extra complete mainlevel shell so the outer electron main shell is further from the nucleus.

Front 30

Define first ionisation energy?

Back 30

The energy required to convert a mole isolated gaseousatoms into a mole of singly positively charged gaseous ions by removing a moleof electrons.

Front 31

Trend in melting and boiling points across a period?

Back 31

The melting/boiling pointsincrease from sodium to aluminium because of the strength of the metallicbonding, the charge on the ions increases so more electrons join the sea ofdelocalised electrons that holds the lattice together.

The melting point ofnon-metals with molecular structures depends on the size of the van der waalsforced between molecules. Silicon is macromolecular with strong covalent bondswhich require a lot of energy to overcome.

Phosphorous, sulphur andchlorine are molecular substances, van der waals forces are weak and need lessenergy to overcome so they have lower boiling/melting points. Of these, sulphuris the biggest molecule so needs more energy to overcome more van der waalsforces.

Front 32

Uses of calcium?

Back 32

CaO and CaCO3 isused to remove sulphur dioxide from flue gases.Ca(OH)2 is used in agriculture toneutralise acid in soils.

Front 33

Uses of Magnesium?

Back 33

Used to extract titaniumfrom its ore. (TiCl4)Mg(OH)2 is used in indigestion tablets asan antacid (milk of magnesia).

Front 34

Uses of Barium

Back 34

Used in ‘barium meals’ ,BaSO4 is opaque to x-rays so makes tissues show up in x-ray imaging.BaCl2 can be used to test for sulfateions.

Front 35

Test for sulfate ions?

Back 35

Acidified BaCl2 is added tothe solution. If a white precipitate of BaSO4 isformed then sulfate ions are present. HCl is used to acidify the solution toget rid of impurities of sulfites and carbonates which would also produce awhite precipitate.

Front 36

Solubility rules for hydroxides (group 2)

Back 36

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Front 37

Solubility rules for Sulphates (group 2)

Back 37

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