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Chemistry > 3.1.2 Group 2 & 3.1.3 Halogens & 3.1.4 Qualitative analysis > Flashcards

3.1.2 Group 2 & 3.1.3 Halogens & 3.1.4 Qualitative analysis Flashcards

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1
Q

are group 2 elements oxidised or reduced

A

oxidised

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2
Q

why is group 2 element a reducing agent

A

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

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3
Q

what sub-shell are the 2 outer electrons in

A

S sub-shell

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4
Q

what do group 2 elements form when they react with oxygen

A

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

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5
Q

group 2 reactants react with water to form …..

A

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

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6
Q

what happens to reactivity as you go down group 2

A

reactivity increases as you go down the group

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7
Q

why does reactivity increase as you go down group 2

A

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

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8
Q

what happens to ionisation energies as you go down group 2

A

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

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9
Q

oxide of group 2 + water=

A

releases hydroxide ions and then form alkaline solution of metal hydroxide

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10
Q

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

A

increases so solutions contain more OH- and are more alkaline

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11
Q

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

A

increases so therefore alkalinity increases

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12
Q

why do farmers add group 2 compounds to there fields

A

to increase the pH of the acidic soils to form water

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13
Q

why are group 2 compounds used in medicines

A

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

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14
Q

what are the halogens at RTP

A

exist as diatomic molecules

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15
Q

trends of halogens as you go down the group

A

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

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16
Q

appearance and state of fluorine at RTP

A

pale yellow gas

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17
Q

appearance and state of chlorine at RTP

A

pale green gas

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18
Q

appearance and state of bromine at RTP

A

red-brown liquid

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19
Q

appearance and state of iodine at RTP

A

shiny grey-black solid

20
Q

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

A

S= 2
P= 5

21
Q

Is a halogen oxidised or reduced

A

reduced
gains 1 electron

22
Q

is a halogen and oxidising or reducing agent

A

oxidising agent

23
Q

what happens to reactivity as you go down the halogens

A

decreases

24
Q

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

A

displacement reaction

25
Q

what other halogens does Cl- react with

A

Br- and I-

26
Q

what other halogens does Br- react with

A

I- only

27
Q

why does reactivity decrease as you go down the halogens

A

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

28
Q

Disproportionation definition

A

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

29
Q

example of disproportionation reaction

A

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

30
Q

benefits of chlorine used in water treatments

A

kills bacteria

31
Q

Cl2 + H2O

A

HClO + HCl

32
Q

reaction to form bleach

A

Cl2 + 2NaOH -> NaClO + NaCl + H2O

33
Q

risks of using chlorine

A

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

34
Q

Test for halide ions

A

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

35
Q

qualitative analysis

A

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

36
Q

carbonate test - CO3 2-

A

add dilute nitric acid to solution
if bubbles its a carbonate

37
Q

how to prove gas is CO2

A

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

38
Q

sulphate test

A

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

39
Q

colour of chlorine ions in silver nitrate and solubility in NH3

A

white
soluble in dilute NH3

40
Q

colour of bromine ions in silver nitrate and solubility in NH3

A

cream
soluble in concentrated NH3

41
Q

colour of iodide ions in silver nitrate and solubility in NH3

A

yellow
insoluble in all NH3

42
Q

what order do the anion tests go in

A

carbonate
sulphate
halides

43
Q

why do sulphate test after carbonate test

A

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

44
Q

why do halide test last

A

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

45
Q

test for ammonium NH4 +

A

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

Chemistry (34 decks)

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