3.1.2 Group 2 & 3.1.3 Halogens & 3.1.4 Qualitative analysis

Question 1

are group 2 elements oxidised or reduced

Answer 1

oxidised

Question 2

why is group 2 element a reducing agent

Answer 2

as it reduces another species as the 2 electrons it loses another species gains to become reduced

Question 3

what sub-shell are the 2 outer electrons in

Answer 3

S sub-shell

Question 4

what do group 2 elements form when they react with oxygen

Answer 4

metal oxide with general formula MO due to 1:1 ratio of the -2 and +2

Question 5

group 2 reactants react with water to form …..

Answer 5

alkaline hydroxide with general formula M(OH)2 and hydrogen gas

Question 6

what happens to reactivity as you go down group 2

Answer 6

reactivity increases as you go down the group

Question 7

why does reactivity increase as you go down group 2

Answer 7

as the atoms of group 2 elements react by losing electrons to form 2+ ions which requires input of 2 ionisation energies.
the ionisation energies decrease as you go down the group due to decrease in attraction between nucleus and outer electrons so less energy is needed to be given in to lose the electron and therefore react. this also causes them to become stronger reducing agents

Question 8

what happens to ionisation energies as you go down group 2

Answer 8

decreases as the attraction between the nucleus and the outer electrons decreases as a result of increasing atomic radius and increasing shielding

Question 9

oxide of group 2 + water=

Answer 9

releases hydroxide ions and then form alkaline solution of metal hydroxide

Question 10

what happens to solubility of hydroxides in water as you go down group 2

Answer 10

increases so solutions contain more OH- and are more alkaline

Question 11

what happens to pH as the solubility of hydroxides increases as you go down group 2

Answer 11

increases so therefore alkalinity increases

Question 12

why do farmers add group 2 compounds to there fields

Answer 12

to increase the pH of the acidic soils to form water

Question 13

why are group 2 compounds used in medicines

Answer 13

used as antacids to help neutralise stomach acid to produce water treating indegestion
Mg(OH)2 + 2HCl -> MgCl2 + 2H2O

Question 14

what are the halogens at RTP

Answer 14

exist as diatomic molecules

Question 15

trends of halogens as you go down the group

Answer 15

more electrons
stronger London forces
more energy required to break IMF
boiling point increases

Question 16

appearance and state of fluorine at RTP

Answer 16

pale yellow gas

Question 17

appearance and state of chlorine at RTP

Answer 17

pale green gas

Question 18

appearance and state of bromine at RTP

Answer 18

red-brown liquid

Question 19

appearance and state of iodine at RTP

Answer 19

shiny grey-black solid

Question 20

how many electrons in the outer P sub-shell and outer S sub-shell of halogens

Answer 20

S= 2
P= 5

Question 21

Is a halogen oxidised or reduced

Answer 21

reduced
gains 1 electron

Question 22

is a halogen and oxidising or reducing agent

Answer 22

oxidising agent

Question 23

what happens to reactivity as you go down the halogens

Answer 23

decreases

Question 24

what reaction do you carry out to show reactivity of the halogens

Answer 24

displacement reaction

Question 25

what other halogens does Cl- react with

Answer 25

Br- and I-

Question 26

what other halogens does Br- react with

Answer 26

I- only

Question 27

why does reactivity decrease as you go down the halogens

Answer 27

atomic radius increases more inner shell so increase in shielding less nuclear attraction

Question 28

Disproportionation definition

Answer 28

a redox reaction in which the same element is both oxidised and reduced

Question 29

example of disproportionation reaction

Answer 29

reaction of chlorine with water and with cold dilute sodium hydroxide= 2 examples

Question 30

benefits of chlorine used in water treatments

Answer 30

kills bacteria

Question 31

Cl2 + H2O

Answer 31

HClO + HCl

Question 32

reaction to form bleach

Answer 32

Cl2 + 2NaOH -> NaClO + NaCl + H2O

Question 33

risks of using chlorine

Answer 33

extremely toxic gas respiratory irritant in small concs and fatal in large concs chlorinated hydrocarbons are formed from drinking water reacting with methane formed by decaying veg is suspected to cause cancer

Question 34

Test for halide ions

Answer 34

add silver nitrate to aqueous halide a white, cream and yellow precipitate will form then add ammonium

Question 35

qualitative analysis

Answer 35

simple observations such as gas bubbles, precipitates, colour change and identification of gases

Question 36

carbonate test - CO3 2-

Answer 36

add dilute nitric acid to solution if bubbles its a carbonate

Question 37

how to prove gas is CO2

Answer 37

bubble gas through lime water and the calcium hydroxide react with CO2 and will turn lime water cloudy

Question 38

sulphate test

Answer 38

add barium nitrate and a white precipitate form as barium sulphate is formed

Question 39

colour of chlorine ions in silver nitrate and solubility in NH3

Answer 39

white soluble in dilute NH3

Question 40

colour of bromine ions in silver nitrate and solubility in NH3

Answer 40

cream soluble in concentrated NH3

Question 41

colour of iodide ions in silver nitrate and solubility in NH3

Answer 41

yellow insoluble in all NH3

Question 42

what order do the anion tests go in

Answer 42

carbonate sulphate halides

Question 43

why do sulphate test after carbonate test

Answer 43

if you carry out sulphate test on a carbonate you get a white precipitate aswell so must carry out carbonate first

Question 44

why do halide test last

Answer 44

silver carbonate and nitrate are both insoluble in water and will form a precipitate in the test so carry out the carbonates and sulphur test before to rule out these possibilities

Question 45

test for ammonium NH4 +

Answer 45

add NaOH (aq) warm and ammonia gas will be produced test with moist litmus paper and if present it will turn blue