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Chemistry > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

What is the appearance and colour of fluorine(pure, non-polar solvents,water)

A

Pure=pale yellow gas
Non polar = reacts with solvent (none)
Water=reacts(none)

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2
Q

What is the appearance and colour of chlorine (pure, non-polar solvents,water)

A

Pure=pale green gas
Non polar=pale green solution
Water=pale green solution

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3
Q

What is the appearance and colour of bromine (pure, non-polar solvents,water)

A

Pure=dark red liquid
Non polar=orange solution
Water=orange solution

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4
Q

What is the appearance and colour of iodine (pure, non-polar solvents,water)

A

Pure=grey solid
Non polar=purple solution
Water=insoluble but forms brown solution if excess KI present

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5
Q

Why do mp and bp increase steadily down the group 7?

A

Increase in vdw due to increased electron and surface area

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6
Q

What happened to oxidising power as you go down the group 7 and why?

A

Decreases as more number of shells more shielding from nucleus thus weaker attraction to electron they want to accept

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7
Q

What happens to reducing power down the group 7 and why?

A

It increases ,(fluoride ions have no significant reducing powers)
Number of shells increase , more shielding of nucleus outer electron become less attracted , easily lost

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8
Q

What is the rule for displacement reactions in group 7?

A

The atoms higher up the group will displace those lower down e.g Cl2 will displace Br-

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9
Q

What happens when a chlorine atom reacts with bromine ions

A

-Chlorine displaces bromine
-Cl gains e- (reduced)
-Br(oxidised)
-orange colour will appear (br)

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10
Q

What happens when chlorine atoms reacts with iodide ions

A

-chlorine displaces iodide
-Cl=reduced=gains e-
-I=oxidised=loses e-
-brown colour will appear

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11
Q

What happens when a bromine atom reacts with iodine ions

A

-bromine displaces iodide
-Br=reduce=gains e-
-I=oxidised loses e-
-brown colour will appear

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12
Q

Reaction of H2SO4 with sodium salts of haldies..

A

H2SO4(l) + NaX(s)NaHSO4(s) + HX(g)
(or H2SO4(l) + X-HSO4- + HX(g))
-hydrogen halide produced
-halogens acts as a base

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13
Q

Reduced of H2SO4 to SO2 ,S,H2S

A

-H2SO4 + 2H+ + 2eSO2 + 2H2O== (S reduced from +6 to +4)
-H2SO4 + 6H+ + 6eS + 4H2O== (S reduced from +6 to 0)
-H2SO4 + 8H+ + 8eH2S + 4H2==(S reduced from 6+ to 2-)

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14
Q

Why is chlorine not oxidised by H2SO4

A

-Cl-=not a strong reducing agent
-thus only an acid based reaction occurs
-H2SO4 + Cl-HSO4- + HCl
-white fumes of HCL will be seen
-the fumes will turn blue litmus paper red

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15
Q

What happens when Br- and H2SO4 react

A

-Br- is a better reducing agent and is oxidised
- the sulphur in the H2SO4 is only reduced from +6 to +4 (SO2).
-The acid-base reaction=H2SO4 + Br-HSO4- +
-H2SO4 + 2H+ + 2Br-SO2 + Br2 + 2H2O (redox reaction)

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16
Q

What happens when I- and H2SO4 react

A

-I- is a good reducing agent and is oxidised
The acid-base reaction
: H2SO4 + I-HSO4- + HI
Redox:
-H2SO4 + 6H+ + 6I-S + 3I2 + 4H2O (sulphur reduced to 0)
-H2SO4 + 8H+ + 8I-H2S + 4I2 + 4H2O(sulphur reduced to 2-)
-H2SO4+ 2I-+2H+SO2 + 2H20 + I2

17
Q

Observation of HSO4 with Br-

A

-white fumes hat turn blue litmus paper red
-red/orange colour of Br2

18
Q

Observation of reactions of H2SO with I-

A
  • White fumes which will turn blue litmus paper red
    -purple colour of I2 vapour
    -smell of rotten eggs due o H2S
19
Q

What do you use to test for halide ions

A

Silver nitrate solution

20
Q

What precipitate do you get when you react with Ag+ with Cl-,Br-,I-?

A

Cl-=white ppt
Br-=cream ppt
I-=yellow ppt

21
Q

Why do you add nitric acid when testing for Halide ions

A

Remove impurities,
Carbonates ,hydroxides = removed as c02 and 0H

22
Q

Why do we have a further reaction to distinguish between halides after Ag+ is used

A

The ppt are similar in colour

23
Q

AgCl dilute/concentrated NH3 observation

A

Ppt dissolves

24
Q

AgBr + concentrated NH3 observation

A

Ppt dissolves with concentrated but not dilute

25
Q

AgI + NH3 observation

A

Ppt does not dissolve for dilute or concentrated

26
Q

Why is the reaction of Cl2 with H2O useful?

A

Makes HCLO (chloric acid) which is effective at killing bacteria:
-used in water to sterilise eg swimming pools
-Small doses as Cl is toxic

27
Q

Symbol Equation of Cl2 +H20

A

-Cl2(g) + H2O(l) == HCl(aq) + HClO(a
-chlorine is oxidised and reduced:
-Cl2= 0
-HCL=-1
-HCLO=+1

28
Q

How is bleach made?

A

Chlorine and NaOH

29
Q

What is the equation for the formation of bleach?

A

2NaOH + Cl2 -> NaClO +NaCl + H2O

30
Q

What is formed when AgBr dissolves in excess ammonia?

A

Ag(NH3)2+ + Br-

Chemistry (28 decks)

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