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A level Chemistry > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

Group 7 elements are

A

non metals and very reactive

they react with metals to form salts

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2
Q

Group 7 element are all

A

very reactive non metals and known as halogens but exist as ions n are instead known as hallowed

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3
Q

at room temperature what does fluorine form?

A

at room temperature fluorine is a gas

and forms a pale yellow colour

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4
Q

at room temperature what does chlorine form

A

at room temperature chlorine si a gas and forms a pale green colour

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5
Q

at room temperature what does bromine form

A

at room temperature bromine is a liquid with red brown or red brown colour

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6
Q

at room temperature what does iodine form

A

iodine forms a solid at room temperature and forms a black colour

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7
Q

As we go down group 7 electronegativity

A

decreases

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8
Q

Why does electronegativity decrease down a group

A

there are more full shells of electrons

there is a greater shielding of outer
electrons

atomic radius increases

and the distances between nucleus and the shared electron pair increases

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9
Q

State the trend in the boiling points of the halogens from fluorine to iodine and explain this trend

A

boiling point increases from fluorine to iodine

this is because the molecule increase in size/molecular mass/ surface area/ number of electrons

this increases the strength of van der waals forces between molecules

therefore more energy is needed to overcome these forces

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10
Q

Halogens can act as a oxidising agent what is the most oxidising agents

A

fluorine and therefore displaces chloride bromide and iodide ions

whilst chlorine displaces bromide and iodide but not fluoride ions

bromine is only able to displace iodide ions

so going down a group oxidising ability decreases

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11
Q

The oxidising ability of the halogens d

and the reducing ability of halides

A

oxidising ability of halogens decrease down a group

and reducing ability of hallides increase down the group

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12
Q

Which reaction takes place between fluoride ions and concentrated sulfuric acid

A

acid base reaction

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13
Q

which reaction take place between chloride ions and concentrated sulfuric acid

A

acid base reaction

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14
Q

Bromide ions react with sulfuric acid to produce

A

an acid base reaction and a redox reaction
producing hydrogen bromide perceived as steamy fumes
and in redox reaction bromine vapour which is perceived as brown colour in the stream fumes

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15
Q

when concentrated sulfuric acid is added to sodium iodide salt we can make several observations & acid base reaction occurs & redox reactions

1) state the chemical formula or the substance which is observed as steamy fumes
2) state the chemical formula to ether substance which is observed as black solid
3) state the chemical formula of the substance which is observed as a yellow solid
4) state the chemical formula of the substance which is observed as the smell of rotten eggs

A

1) HI (g) (
2) I2 (g)
3) S (s)
4) H2S (g)

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16
Q

what is the name given to a halogen that has gained an electron

A

halide

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17
Q

under standard conditions halogens exist as

A

as a molecule containing 2 atoms
the boiling point of the halogens increases doen the group as the number of electrons increases and thus the strength of van der waals forces increases

18
Q

Which of the following will oxidise iodide ions to iodine?

1) F2
2) Cl2
3) Br2

A

down the group the ability of shooters to act as an oxidising agent decreases

this makes f2 cl2 br2 stronger oxidising agents than i2

therefore f2 cl2 and br2 will oxidise I- to I2

19
Q

Complete the balanced half equation for the oxidation of bromide

1) 2Br —>

A

Br2 + 2e-

20
Q

complete the balanced half equation for the reduction of fluorine

2) F2 + 2e- —>

A

2F-

21
Q

State the overall equation for the oxidation of bromide with fluorine

A

2Br- + F2 —> Br2 + 2F-

22
Q

Which half-life is the strongest reducing agent

1) fluoride
2) chloride
3) bromide
4) iodide

A

Iodide as doen a group hallides reducing power increases

23
Q

State the acid base reaction when sodium bromide reacts with the concentrated sulfuric acid

A
24
Q

complete the following redox reaction equation for bromides reaction with concentrated sulfuric acid

2H+ + 2Br- + H2SO4 (l) —>

A

2H+ + 2Br- + H2SO4 (l) —> SO2 (g) + 2H2O (l) + Br2 (l)

25
Q

Silver nitrate react with the different halide ions to form silver hallides
state what would be observed when each of the following forms

A

silver fluoride -> forms no precipitate
silver chloride -> white precipitate
silver bromide -> creamy precipitate
silver iodide -> pale yellow precipitate

26
Q

What happens if the aqueous solution contains impurities like hydroxides or carbonates ?

2Ag+ + CO23- —>
Ag+ + OH- —>

A

Ag2CO3 (s) then silver carbonate would form
AgOH (s) then silver hydroxide would form
since both are insoluble in water it would precipitate and invalidate the test

27
Q

thow do we remove this to purify the test?

A

we need to acidify the solution to do this we dilute the solution with nitric acid

which react with any soluble hydroxide to form water and any soluble carbonates to form carbon dioxide and water

28
Q

How to identify silver hallides ?

A

after adding silver nitrate into hallides ions we might not be able to tell the precipitates so we need to add dilute ammonia to the solution

silver chloride will dissolve to forms. colourless solution

leaving our 2 finals (Br - and I)

last step is to add concentrated ammonia which makes silver bromide dissolve
leaving silver iodide which is insoluble in any ammonia solvent

29
Q

An aqueous solution was acidified with dilute hydrochloric, and silver nitrate solution was then added.
A precipitate formed

Dilute ammonia solution was then added to the solution, but the
precipitate did not dissolve.

Concentrated ammonia solution was then added, but the precipitate still

identify the hallide ion in the solution

A

iodide is the hallide

30
Q

Why is HClO called chloric (i) acid

A

because it’s chlorine atom has an oxidation state of 1+

31
Q

The reaction between chlorine and water is Cl2 (ag) + H2O () = HCI (ag) + HCIO (ag).
Which of the following changes would shift the equilibrium to the left?

A)Increasing the concentration of Cl2 (ag)

B)Increasing the concentration of HC1 (ag)

C)Adding water to the reaction vessel

D) Increasing the pressure

A

By increasing the concentration of Cl2 and adding water equilibrium would shift to the right

increasing the pressure will not affect equilibrium bcs none of the reacting species are gaseous

the only option left is increasing concentration of HCl
the equilibrium shifts to opposo the change removing the HCl by producing more Cl2 and H2O

32
Q

The reaction between chlorine and water is Cly (ag) + H, 0 (1) # HCI (ag) + HCIO (ag).
Give the oxidation states of chlorine in the following species:
1) Cl2
2) HCI
3) HCIO
4) This type of reaction is known as a/an

A

1) 0
2) -1
3) +1
4) known as an disproportionation reaction

33
Q

When chlorine is first added to pools, a greenish tint forms.

1) This is due to the presence of…
2) Over time the greenish tint disappears. This is due tot he chlorine reacting with water to form…

A

1) Cl2 / chlorine

2) HCl (aq) + HCIO

34
Q

Why is HCIO more useful than HCl for sterilising pools?

A

The bacteria in the water are killed by oxidation using HCIO

35
Q

Why do outdoor pools require more chlorine to sterilise them than indoor pools?

A

In the presence of sunlight, chlorine reacts with water to form hydrochloric acid and oxygen, in an irreversible reaction

in outdoor pools, there is brighter sunlight so this reaction happens rapidly
this causes chlorine to be lost from pools meaning less chlorine available to restrict with water to form chloric (I) acid which is the oxidising agent needed to kill bacteria

therefore outdoor pools require more chlorine to sterilise them than indoor pools

36
Q

Which of the following statements is true about the chlorination of water supplies?
Select all that apply

A) Chlorine is added to help sterilise water supplies.

B) Chlorine levels in tap-water need to be closely monitored.

C) Chlorine is toxic to humans even at very low concentrations.

D) Chlorination can be considered wasteful because most tap-water is not used for drinking.

E) Chlorination has not saved many lives.

A

A B D

37
Q

Which of the following species is an oxidising agent?

A) HCIO
B) HCl
C) NaClO
D) NaCl
E) H2O
A

A and C

38
Q

which of the following is a disproportionation reaction?

A

B and D

bcs

39
Q

Is the reaction with chlorine reversible?

A

the reaction between chlorine and water without sunlight is reversible

40
Q

Which of the following is a typical example of a use for NaClO (aq)

A

household bleach to kill bacteria and remove stains

A level Chemistry (12 decks)

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