REACTIVITY TRENDS

Question 1

What happens to ionisation and reactivity as you move down group 2

Answer 1

First ionisation energy decreases as atomic radius increases and so reactivity increases as outer electrons are further from the nucleus so attraction is weaker

Question 2

What happens to nuclear charge as you move down groups and how does this affect ionisation

Answer 2

number of protons in the atom will increase down the group, so nucleus will become more positively charged, however as the atomic radius increases as number of electron shells increases, this overrides the effect of the increased nuclear charge and ionisation energy will still decrease

Question 3

what happens group 2 metals react with water

Answer 3

they form bases, metal hydroxides in particular

Question 4

reactions with water down group 2

Answer 4

More reactivity, as atoms are larger so more electron shielding

BERYLIUM DOES NOT REACT WITH WATER

Question 5

What happens when magnesium reacts with steam

Answer 5

will form magnesium oxide and will react vigorously

Question 6

what happens when Group 2 elements react with oxygen

Answer 6

they are oxidised (obviously) and will form metal oxides in a redox reaction

Question 7

state of group 2 oxides and what happens when they react with water

Answer 7

they are white solids

form bases when added to water (hydroxides)

Question 8

Group 2 hydroxide trends down the group

Answer 8

become more strongly alkaline as they become more soluble and OH- ions are more likely to be released

Question 9

Neutralisation and example of a group 2 oxide and hydroxide with acid

Answer 9

will form a group 2 salt and water

CaO + 2HCl –> CaCl2 + H2O

Ca(OH)2 + H2SO4 –> CaSO4 + 2H2O

Question 10

Use of a group 2 hydroxide in nature

Answer 10

Calcium hydroxide is used to neutralise acidic soils to allow some crops or plants to grow if the pH is too low

Question 11

Use of a group 2 hydroxide in medicine

Answer 11

Magnesium hydroxide is used to neutralise excess stomach acid as will react to form water and a magnesium salt

Question 12

Trend of boiling points effect on states down group 7

Answer 12

Boiling point increases as London forces increase due to increasing size and mass of atoms

and so physical state goes from gas down to solid as you move down

Question 13

Electronegativity trend down group 7

Answer 13

decreases as the atoms get larger so electron shielding increases so ability to attract electrons in a covalent bond will decrease

Question 14

How can displacement reactions of halogens be observed

Answer 14

hexane is added to the aqueous solution and the halogen will dissolve readily in the solvent causing a coloured organic layer to form above the aqueous layer

Question 15

how are halide ions displaced

Answer 15

more reactive halogen will displace less reactive halide ions

Question 16

Reactivity of halogens down the group

Answer 16

decreases as for a reaction to occur the halogen will need to gain an electron, as electronegativity decreases down the group, so does reactivity

HALOGENS ARE LESS OXIDISING AS YOU MOVE DOWN THE GROUP AS THEY ARE LESS READILY REDUCED

Question 17

Reaction of KCl and Cl2 and colour changes

Answer 17

no reaction, aqueous and organic solution are both colourless

Question 18

Reaction of KBr and Cl2 and colour changes

Answer 18

Chlorine will displace the bromide ions

aqueous solution will turn yellow and the organic solution will turn orange

Question 19

Reaction of KI and Cl2 and colour changes

Answer 19

Chlorine will displace iodide ions

aqueous solution will go brown and organic layer will be purple

Question 20

Reaction of KCl / KBr and Br2 and colour changes

Answer 20

no reaction

aqueous solution will be yellow and organic layer will be orange

Question 21

KI and Br2 reaction

Answer 21

Bromine will displace iodide ions

aqueous will be brown and organic layer will be purple

Question 22

Reaction of I2 with KCl, KBr, KI

Answer 22

no reactions

aqueous solution will be brown and organic layer will be purple

Question 23

How to test for halides and corresponding precipitates

Answer 23

Add dilute HNO3 and then AgNO3, the precipitate colour will help identify the halide ion

Cl- will give a white precipitate (AgCl)

Br- will give a cream precipitate (AgBr)

I- will give a yellowy precipitate (AgI)

Question 24

Why is HNO3 added when testing for halides

Answer 24

to react with any other anions other than halides (to prevent false results)

Question 25

How to FURTHER TEST for halide ions

Answer 25

add ammonia solution to precipitates obtained

Cl- precipitate dissolves in dilute NH3

Br- precipitate dissolves in concentrated NH3

I- precipitate is insoluble in concentrated NH3

Question 26

How is bleach made and show equation

Answer 26

a disproportionation reaction

mix chlorine with sodium hydroxide forms sodium chlorate(1)

2NaOH + Cl2 –> NaClO + NaCl + H2O

Question 27

What is a disproportionation reaction

Answer 27

One in which an element has been simultaneously reduced and oxidised

Question 28

Uses of bleach

Answer 28

Adding chlorine to water produces chlorate ions which kill bacteria

Can be used to bleach fabrics to remove colour

used as a cleaning agent

Question 29

Water sterilisation reactions

Answer 29

H2O + Cl2 –> HCl + HClO

HClO + H2O <–> ClO- + H3O+

Question 30

Advantages and disadvantages to chlorinating drinking water

Answer 30

• Kills microorganisms that cause disease
• long lasting so reduces build up of bacteria further down supply
• reduces growth of algae
• chlorine gas is toxic
• liquid chlorine causes sever chemical burns
• chloroalkanes could form which are linked to causing cancer

Question 31

Ethical issues with chlorination water and alternatives for water sterilization

Answer 31

Some claim it is forced medication to whole population

ozone is a powerful [O] that kills microorganisms, it is expensive to produce and has short half life

UV light damages DNA of microorganisms, but is ineffective in cloudy water and wont prevent further contamination

Question 32

Test for ammonium compounds

Answer 32

add NaOH and gently heat, ammonia will be produced if present

use damp red litmus, ammonia will dissolve in water and turn litmus blue

Question 33

test for hydroxides

Answer 33

As they are alkaline, they turn red litmus paper blue

Question 34

Test for carbonates

Answer 34

add acid, which should make CO2, when bubbled through limewater it will turn cloudy

Question 35

test for sulfates

Answer 35

add hydrochloric acid to remove carbonates

add barium chloride, barium sulphate should be produced and so will see a white precipitate

Question 36

Order or testing for carbonates, sulphates, halides

Answer 36

test for CO2 first, then add barium chloride to test for sulphates, then silver nitrate to test for halides

Question 37

Neutralisation and example of a group 2 oxide and hydroxide with acid

Answer 37

will form a group 2 salt and water