Reactivity Trends (8)

Question 1

How many electrons in a Group 2 outer shell

Answer 1

2

Question 2

What part of the redox reaction do Group 2 elements undergo?

Answer 2

Oxidation. 2 of their electrons are removed in order to have the same structure as the nearest noble gas.

Question 3

Are Group 2 elements oxidising or reducing agents

Answer 3

They are reducing agents as they are oxidised and the 2 electrons removed from them will be accepted by another element which will become reduced.

Question 4

Group 2 elements and oxygen

Answer 4

They will react with oxygen to form metal oxides with the molecular formula MO as the +2 and -2 cancel out.

Question 5

Magnesium + Oxygen

Answer 5

Reacts to make white magnesium oxide and burns with a bright white light. Mg is oxidised and O2 is reduced.

Question 6

Group 2 elements and water

Answer 6

React to form a metal hydroxide M(OH)2 which is alkali because it releases OH- ions. Water reacts very slowly with the top elements, but as you go down the group it becomes more vigorous.

Question 7

Magnesium + Water

Answer 7

React really slowly because magnesium isn’t too reactive.

Question 8

Group 2 elements and dilute acids

Answer 8

metal + acid -> salt + hydrogen

Question 9

What happens to reactivity down Group 2

Answer 9

As you go down Group 2, the reactivity increases because of the first and second ionisation energies. It is a lot easier to remove the outer electrons on the lower elements due to electron shielding etc.. so the lower you go, the more reactive they are.

Question 10

Group 2 oxides and water

Answer 10

Makes the group 2 ion and 2 hydroxide ions which means it becomes an alkali solution. If the solution becomes saturated, the M2+ ion and 2OH- ion will combine to make M(OH)2 precipitate.

Question 11

What happens to solubility of metal hydroxides down Group 2

Answer 11

As you go down the group, the solubility of hydroxides in water will increase because the metals are more reactive so will be more attracted to the water and will result in more OH- ions being released.

Question 12

What is the trend in pH down Group 2 hydroxides?

Answer 12

The pH will increase as you go down group 2 as it is becoming more alkali as you go down. Magnesium is only slightly soluble in water so it will only release a few OH- ions, whereas Barium is more soluble so, will release a lot more OH- ions and have a bigger pH.

Question 13

Group 2 compound uses

Answer 13

Used in agriculture or medicine

Question 14

Group 2 uses in agriculture

Answer 14

The use of Ca(OH2) which is white lime and neutralises acid in soil

Question 15

Group 2 uses in medicine

Answer 15

Treats acid indigestion by neutralising it, and is called antacid. Neutralised the HCl in your stomach.

Question 16

How to test for pH of Group 2 oxides

Answer 16

Add a spatula of metal oxide to a test tube and add water. Shake the tube and you won’t have enough water to dissolve all the metal oxide so you will have precipitate at the bottom and a solution which is your metal hydroxide. Test the pH of this to see what you get.

Question 17

Halogens

Answer 17

Group 7 elements that are the most reactive non-metal elements

Question 18

How do halogens exist?

Answer 18

As diatomic molecules with simple molecular structures. They exist in all states.

Question 19

What is the trend of boiling points?

Answer 19

The boiling point will increase down the group and this is because they exist as diatomic molecules, so as you go down the group, the number of electrons increases, so the number of London forces increases. This means that the energy required to break the bond between them will get higher.

Question 20

Fluorine state and colour

Answer 20

pale yellow gas

Question 21

Chlorine state and colour

Answer 21

pale green gas

Question 22

Bromine state and colour

Answer 22

red-brown liquid

Question 23

Iodine state and colour

Answer 23

black solid

Question 24

Astatine state and colour

Answer 24

never been seen

Question 25

What part of the redox reaction do halogens undergo?

Answer 25

They undergo a reduction as they gain an electron and they are oxidising agents as they will oxidise other elements.

Question 26

Halogen - Halide Displacement Reaction

Answer 26

This is where the halogens will displace halide ions and is used to show that reactivity decreases down the group. You add a halogen to different halide solutions and see if the halogen is more reactive than the halide If it is then a reaction will occur and a colour change will take place

Question 27

colour of chlorine in water

Answer 27

pale green

Question 28

colour of bromine in water

Answer 28

orange

Question 29

colour of iodine in water

Answer 29

brown

Question 30

What can you use as a solvent for halogens instead of water?

Answer 30

Cyclohexane because the bromine and iodine in water solutions are similar colours in water. The halogens will dissolve more readily in cyclohexane so will have more distinguishable colours

Question 31

colour of chlorine in cyclohexane

Answer 31

pale green

Question 32

colour of bromine in cyclohexane

Answer 32

orange

Question 33

colour of iodine in cyclohexane

Answer 33

purple

Question 34

Results of the displacement reaction

Answer 34

Chlorine has reacted with both bromine and iodine so has displaced both reactions Bromine reacted with iodine only and displaced it, but not with chlorine Iodine didn't react with any.

Question 35

What do the halogen halide reactions prove?

Answer 35

That reactivity decreases down the group

Question 36

What is the reactivity trend and why?

Answer 36

The reactivity decreases down the group. When halogens react, they gain an electron so the more shells they have, the greater the atomic radii, and the smaller the nuclear charge, the less attracted an electron on another atom will be, so it will be harder for it to react.

Question 37

Disproportionate Reactions

Answer 37

This is when the same element is both reduced and oxidised in the same reaction. Two examples are chlorine + water and chlorine + dilute sodium hydroxide

Question 38

Chlorine + water

Answer 38

The chlorine will be reduced into hydrochloric acid and chloric acid which can kill bacteria

Question 39

Chlorine + dilute sodium hydroxide

Answer 39

The chlorine is reduced into NaCl and the chlorine is oxidised into NaClO which is sodium chlorate which is used as bleach. Water is also formed.

Question 40

Benefits of chlorine

Answer 40

Can kill harmful bacteria, so have been made into tablets and added to drinking and pool water in order to make it purified.

Question 41

Risks of chlorine

Answer 41

As a gas, it's extremely harmful as it can irritate the lungs. It can also combine with methane to form chlorinated hydrocarbons which can cause cancer

Question 42

Quantitative Analysis

Answer 42

Doing an experiment and taking measurements that are with numbers to calculate the result of the experiment

Question 43

Qualitative Analysis

Answer 43

Relying on observations like colour, gas bubbles etc to determine the result of your experiment

Question 44

Carbonate Test

Answer 44

Carbonates are CO3 2- anions that react with dilute acid to form carbon dioxide gas. To test for them put dilute nitric acid on the compound to be tested. If you see bubbles, the unknown compound could be a carbonate You can prove the gas is carbon dioxide by doing a lime water test.

Question 45

Lime Water Test

Answer 45

You run carbon dioxide through lime water which is calcium carbonate. This will form a cloudy white precipitate.

Question 46

Sulphate Test

Answer 46

Most sulphates are soluble in water, but barium sulphate is very insoluble. So if you want to test a compound to see if it's a sulphate, add barium nitrate and see if any barium sulphate precipitate it formed. It should be a white precipitate.

Question 47

Halide Test

Answer 47

Most halides are soluble in water, but silver halides are not. So when you want to test for halide ions: you add in silver nitrate you then form a silver halide precipitated that can be different colours depending on the halide Add dilute then concentrated aqueous ammonia to test the solubility as they can be different colours

Question 48

Silver chloride precipitate

Answer 48

white

Question 49

Silver bromide precipitate

Answer 49

cream

Question 50

Silver iodide precipitate

Answer 50

yellow

Question 51

Silver chloride solubility

Answer 51

soluble in dilute ammonia

Question 52

Silver bromide precipitate

Answer 52

soluble in concentrated ammonia

Question 53

Silver iodide precipitate

Answer 53

insoluble in concentrated ammonia

Question 54

The sequence of tests when trying to recognise a compound.

Answer 54

Carbonate Test, Sulphate Test, Halide Test Carbonate Test goes first as it doesn't have the possibility of an incorrect experiment, sulphates and halides don't react with dilute acid to form bubbles Sulphate Test goes after because barium also reacts with carbonate to form a white precipitate, so you have to determine there's no carbonate first. Halide Test last because silver sulphate and carbonate both form precipitates.

Question 55

What if you want to analyse a mixture of ions?

Answer 55

You first do the carbonate test and keep adding nitric acid until the bubbling stop so you can get rid of all the carbonate ions. Then do the sulphate test and add barium nitrate to the solution until all of the barium sulphate has precipitated out, then just filter it out. Do the halide test last and then determine which silver halide precipitate you get.

Question 56

Ammonium Ion Test

Answer 56

You add sodium hydroxide to the solution you want to test. It will form ammonia gas and water. The ammonia gas will then evaporate when warmed and you can smell it, or you can put a paper pH indicator and it will turn blue.