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Separate Chemistry > T3: Group 2 and Group 7 > Flashcards

T3: Group 2 and Group 7 Flashcards

1
Q

reducing agent

A

electron donor

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2
Q

reducing strength of halides

A
  • increases down the group
  • ionic radius increases
  • weaker attraction between outer e- and nucleus
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3
Q

H2SO4 -> SO2

A

Br2, I2 - acidic chocking gas

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4
Q

H2SO4 -> S

A

I2 - yellow solid

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5
Q

H2SO4 -> H2S

A

I2 - bad egg smell

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6
Q

Role of H2SO4 with Br2, I2

A

oxidising agent

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7
Q

iodine half equation

A

2I- -> I2 + 2e-

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8
Q

I2 appears as…

A

a black solid

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9
Q

bromine half equation

A

2Br- -> Br2 + 2e-

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10
Q

Br2 appears as…

A

brown fumes

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11
Q

H2SO4 -> SO2 half equation

A

2e- + 2H+ H2SO4 -> SO2 + 2H2O

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12
Q

H2SO4 -> S half equation

A

6e- + 6H+ H2SO4 -> S + 4H2O

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13
Q

H2SO4 -> H2S half equation

A

8e- + 8H+ H2SO4 -> H2S + 4H2O

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14
Q

Role of H2SO4 with F, Cl

A

an acid

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15
Q

flourine half equation

A

H+ + F- -> HF

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16
Q

flourine observation

A

misty fumes

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17
Q

NaF + H2SO4 ->

A

NaHSO4 + HF

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18
Q

chlorine half equation

A

H+ + Cl- -> HCl

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19
Q

chlorine observation

A

misty fumes

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20
Q

NaCl + H2SO4 ->

A

NaHSO4 + HCl

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21
Q

NaBr + H2SO4 combined half equation (SO2)

A

2Br- + 2H+ + H2SO4 -> SO2 + Br2 + 2H2O

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22
Q

NaI + H2SO4 combined half equation (S)

A

6I- + 6H+ + H2SO4 -> S + 3I2 + 4H2O

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23
Q

NaI + H2SO4 combined half equation (H2S)

A

8I- + 8H+ + H2SO4 -> H2S + 4I2 + 4H2O

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24
Q

procedure to identify halide tests

A

1 dissolve sample in water (in not already in aq solution)
2 add HNO3 acid
3 add AgNO3(aq) solution
4 if halide is present you will see one of the observations
F- = no precipitate
Cl- = white precipitate
Br- = cream precipitate
I- = yellow precipitate

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25
Q

2 reasons why is HNO3 acid added

A

1 used to remove any possible CO32- impurities, which could give a false positive
2 DON’T use HCL or H2SO4 acid for this step

26
Q

what 2 reactions (2 equations) will happen if you fail to remove any possible CO32- impurities, which could give a false positive

A

2Ag+(aq) + CO32-(aq) -> Ag2CO3(s) [WHITE precipitate]
2H+(aq) + CO32-(aq) -> CO2(g) + H2O(l) [EFFERVESCENCE]

27
Q

what is the problem with the 1st observations seen in the test tubes (halide tests)

A

it can be difficult to tell whether you have a white, cream or yellow ppt

28
Q

what happens because of the problem of these observations (halide tests)

A

further steps are carried out to positively identify the halide

29
Q

what are the further steps that are carried out (for 2nd observation - halide tests)

A

add dilute NH3 to the sample
Cl- = white precipitate dissolves
Br- = cream precipitate insoluble
I- = yellow precipitate insoluble

30
Q

what are the further steps that are carried out (for 3rd observation - halide tests)

A

add concentrated NH3 to the sample
Br- = cream precipitate dissolves
I- = yellow precipitate insoluble

31
Q

what are the precipitates (AgNO3 - 4 ionic equations - halide tests)

A

Ag+(aq) + F-(aq) -> AgF(aq)
Ag+(aq) + CL-(aq) -> AgCl(s)
Ag+(aq) + Br-(aq) -> AgBr(s)
Ag+(aq) + I-(aq) -> AgI(s)

32
Q

What does the NH3 do? (halide tests)

A

AgCl(s) + 2NH3(aq) -> [Ag(NH3)2]+(aq) + Cl-(aq)
AgBr(s) + 2NH3(aq) -> [Ag(NH3)2]+(aq) + Br-(aq)

33
Q

Summary of Halide Tests

A
34
Q

trend of oxidising ability of halogens

A
  • decreases down group
  • larger radius
  • weaker attraction between nucleus and outer e-
35
Q

3 ionic equations for halogen displacement reactions (halogens and halides)

A

Cl2 + 2Br- -> Br2 + 2Cl-
Cl2 + 2I- -> I2 + 2Cl-
Br2 + 2I- -> I2 + 2Br-

36
Q

bromine observation in halogen displacement reactions

A

orange solution

37
Q

iodine observation in halogen displacement reactions

A

brown solution

38
Q

summary of halogen displacement reactions (halogens and halides)

A
39
Q

why is chlorine added to water

A

to kill bacteria

40
Q

why is chlorine added in low conc

A

its toxic

41
Q

Cl2 + H2O ⇌

A

HCL + HCLO

42
Q

what type of reaction is this: Cl2 + H2O ⇌ HCl + HClO

A
  • disproportionation
  • Cl2 reduced to HCl (OXS change 0 to -1)
  • Cl2 oxidised to HClO (OXS change 0 to +1)
43
Q

the reactivity of Group 2 metals…

A

increases down the group

44
Q

group 2 with liquid water reaction where X is metal

A

X(s) + 2H2O(l) -> X(OH)2(aq) + H2(g)

45
Q

Mg reaction with steam

A

Mg(s) + H2O(g) -> MgO(s) + H2(g)

46
Q

observations of this reaction: Mg(s) + H2O(g) -> MgO(s) + H2(g)

A

white solid produced (MgO)
bright white light

47
Q

equation for Mg reaction to extract Ti from TiCl4

A

TiCl4 + 2Mg -> 2MgCl2 + Ti

48
Q

role of Mg in this reaction: TiCl4 + 2Mg -> 2MgCl2 + Ti

A

Mg OXS changes from 0 to +2
Mg is oxidised -> reducing agent

49
Q

solubility of group 2 hydroxides…

A

increases down the group

50
Q

simplest ionic equation (group 2 hydroxides)

A

Mg2+(aq) + 2OH-(aq) -> Mg(OH)2(s)

51
Q

observation of this reaction: Mg2+(aq) + 2OH-(aq) -> Mg(OH)2(s)

A

white precipitate forms

52
Q

what could you use to test for the presence of Mg2+ ions in a solution

A

NaOH(aq)

53
Q

what could you use to test for the presence of OH- ions in a solution

A

Mg(NO3)2(aq)

54
Q

uses of magnesium hydroxide

A
  • indigestion relief
  • often called ‘milk of magnesia’
  • neutralises stomach acid
55
Q

solubility of group 2 sulphates…

A

decreases down the group

56
Q

simplest ionic equation (group 2 sulphates)

A

Ba2+(aq) + SO42-(aq) -> BaSO4(s)

57
Q

observation of this reaction: Ba2+(aq) + SO42-(aq) -> BaSO4(s)

A

white precipitate forms

58
Q

what could you use to test for the presence of Ba2+ ions in a solution

A

H2SO4(aq)

59
Q

what could you use to test for the presence of SO42- ions in a solution

A

BaCl2(aq) ACIDIFIED

60
Q

uses of barium sulphate

A
  • stomach X-rays
  • barium meal
  • insoluble -> wont kill you

Separate Chemistry (6 decks)

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