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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
2 reasons why is HNO3 acid added
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
what 2 reactions (2 equations) will happen if you fail to remove any possible CO32- impurities, which could give a false positive
*2Ag+(aq) + CO32-(aq) -> Ag2CO3(s)* [WHITE precipitate] *2H+(aq) + CO32-(aq) -> CO2(g) + H2O(l)* [EFFERVESCENCE]
27
what is the problem with the 1st observations seen in the test tubes (halide tests)
it can be difficult to tell whether you have a white, cream or yellow ppt
28
what happens because of the problem of these observations (halide tests)
further steps are carried out to positively identify the halide
29
what are the further steps that are carried out (for 2nd observation - halide tests)
add dilute NH3 to the sample Cl- = white precipitate dissolves Br- = cream precipitate insoluble I- = yellow precipitate insoluble
30
what are the further steps that are carried out (for 3rd observation - halide tests)
add concentrated NH3 to the sample Br- = cream precipitate dissolves I- = yellow precipitate insoluble
31
what are the precipitates (AgNO3 - 4 ionic equations - halide tests)
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
What does the NH3 do? (halide tests)
AgCl(s) + 2NH3(aq) -> [Ag(NH3)2]+(aq) + Cl-(aq) AgBr(s) + 2NH3(aq) -> [Ag(NH3)2]+(aq) + Br-(aq)
33
Summary of Halide Tests
34
trend of oxidising ability of halogens
- decreases down group - larger radius - weaker attraction between nucleus and outer e-
35
3 ionic equations for halogen displacement reactions (halogens and halides)
Cl2 + 2Br- -> Br2 + 2Cl- Cl2 + 2I- -> I2 + 2Cl- Br2 + 2I- -> I2 + 2Br-
36
bromine observation in halogen displacement reactions
orange solution
37
iodine observation in halogen displacement reactions
brown solution
38
summary of halogen displacement reactions (halogens and halides)
39
why is chlorine added to water
to kill bacteria
40
why is chlorine added in low conc
its toxic
41
Cl2 + H2O ⇌
HCL + HCLO
42
what type of reaction is this: Cl2 + H2O ⇌ HCl + HClO
- disproportionation - Cl2 reduced to HCl (OXS change 0 to -1) - Cl2 oxidised to HClO (OXS change 0 to +1)
43
the reactivity of Group 2 metals...
increases down the group
44
group 2 with liquid water reaction where X is metal
X(s) + 2H2O(l) -> X(OH)2(aq) + H2(g)
45
Mg reaction with steam
Mg(s) + H2O(g) -> MgO(s) + H2(g)
46
observations of this reaction: Mg(s) + H2O(g) -> MgO(s) + H2(g)
white solid produced (MgO) bright white light
47
equation for Mg reaction to extract Ti from TiCl4
TiCl4 + 2Mg -> 2MgCl2 + Ti
48
role of Mg in this reaction: TiCl4 + 2Mg -> 2MgCl2 + Ti
Mg OXS changes from 0 to +2 Mg is oxidised -> reducing agent
49
solubility of group 2 hydroxides...
increases down the group
50
simplest ionic equation (group 2 hydroxides)
Mg2+(aq) + 2OH-(aq) -> Mg(OH)2(s)
51
observation of this reaction: Mg2+(aq) + 2OH-(aq) -> Mg(OH)2(s)
white precipitate forms
52
what could you use to test for the presence of Mg2+ ions in a solution
NaOH(aq)
53
what could you use to test for the presence of OH- ions in a solution
Mg(NO3)2(aq)
54
uses of magnesium hydroxide
- indigestion relief - often called 'milk of magnesia' - neutralises stomach acid
55
solubility of group 2 sulphates...
decreases down the group
56
simplest ionic equation (group 2 sulphates)
Ba2+(aq) + SO42-(aq) -> BaSO4(s)
57
observation of this reaction: Ba2+(aq) + SO42-(aq) -> BaSO4(s)
white precipitate forms
58
what could you use to test for the presence of Ba2+ ions in a solution
H2SO4(aq)
59
what could you use to test for the presence of SO42- ions in a solution
BaCl2(aq) ACIDIFIED
60
uses of barium sulphate
- stomach X-rays - barium meal - insoluble -> wont kill you

Separate Chemistry (10 decks)

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