Group 7

Question 1

Group 7 elements are

Answer 1

non metals and very reactive

they react with metals to form salts

Question 2

Group 7 element are all

Answer 2

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

Question 3

at room temperature what does fluorine form?

Answer 3

at room temperature fluorine is a gas

and forms a pale yellow colour

Question 4

at room temperature what does chlorine form

Answer 4

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

Question 5

at room temperature what does bromine form

Answer 5

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

Question 6

at room temperature what does iodine form

Answer 6

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

Question 7

As we go down group 7 electronegativity

Answer 7

decreases

Question 8

Why does electronegativity decrease down a group

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

The oxidising ability of the halogens d

and the reducing ability of halides

Answer 11

oxidising ability of halogens decrease down a group

and reducing ability of hallides increase down the group

Question 12

Which reaction takes place between fluoride ions and concentrated sulfuric acid

Answer 12

acid base reaction

Question 13

which reaction take place between chloride ions and concentrated sulfuric acid

Answer 13

acid base reaction

Question 14

Bromide ions react with sulfuric acid to produce

Answer 14

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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

halide

Question 17

under standard conditions halogens exist as

Answer 17

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

Question 18

Which of the following will oxidise iodide ions to iodine?

1) F2
2) Cl2
3) Br2

Answer 18

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

Question 19

Complete the balanced half equation for the oxidation of bromide

1) 2Br —>

Answer 19

Br2 + 2e-

Question 20

complete the balanced half equation for the reduction of fluorine

2) F2 + 2e- —>

Answer 20

2F-

Question 21

State the overall equation for the oxidation of bromide with fluorine

Answer 21

2Br- + F2 —> Br2 + 2F-

Question 22

Which half-life is the strongest reducing agent

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

Answer 22

Iodide as doen a group hallides reducing power increases

Question 23

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

Question 24

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

2H+ + 2Br- + H2SO4 (l) —>

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What happens if the aqueous solution contains impurities like hydroxides or carbonates ? 2Ag+ + CO23- —> Ag+ + OH- —>

Answer 26

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

Question 27

thow do we remove this to purify the test?

Answer 27

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

Question 28

How to identify silver hallides ?

Answer 28

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

Question 29

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

Answer 29

iodide is the hallide

Question 30

Why is HClO called chloric (i) acid

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

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

Question 33

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…

Answer 33

1) Cl2 / chlorine | 2) HCl (aq) + HCIO

Question 34

Why is HCIO more useful than HCl for sterilising pools?

Answer 34

The bacteria in the water are killed by oxidation using HCIO

Question 35

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

Answer 35

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

Question 36

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.

Answer 36

A B D

Question 37

Which of the following species is an oxidising agent? ``` A) HCIO B) HCl C) NaClO D) NaCl E) H2O ```

Answer 37

A and C

Question 38

which of the following is a disproportionation reaction?

Answer 38

B and D | bcs

Question 39

Is the reaction with chlorine reversible?

Answer 39

the reaction between chlorine and water without sunlight is reversible

Question 40

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

Answer 40

household bleach to kill bacteria and remove stains