Group 7 (Halogens)

Question 1

What happens when you mix Cl2 with:
Cl-, Br-, I- ?

Answer 1

add Cl- = no change
add Br- = solution turns orange
add I- = solution turns brown

Question 2

What happens when you mix Br2 with:
Cl-, Br-, I- ?

Answer 2

add Cl- = no change
add Br- = no change
add I- = solution turns orange

Question 3

What happens when you mix I2 with:
Cl-, Br-, I- ?

Answer 3

no change for all reactions

Question 4

How does oxidising power change as you go down the group?

Answer 4

It increases

Question 5

How does atomic radius change as you go down the group?

Answer 5

It increases (amount of shells increases)

Question 6

How does electronegativity change as you go down the group?

Answer 6

It decreases (as you go down the group shielding effect increases)

Question 7

How does melting and boiling points change as you go down the group?

Answer 7

Increases as the vdw forces experienced increases as molecules have more electrons

Question 8

How does first ionisation energy change as you go down the group?

Answer 8

Decreases as atomic radius increases

Question 9

Halides are better reducing agents as you go .. ?

Answer 9

Down the group (as they oxidise easier)

Question 10

NaCl* + H2SO4 forms …
*substitute any halide

Answer 10

NaHSO4 + HCl*
*substitute any halide

Question 11

What is observed when you react sodium halides with conc sulfuric acid

Answer 11

Misty white fumes

Question 12

HBr + H2SO4 forms …
(or HI)

Answer 12

Br2 + SO2 + H2O
(or I2)

Question 13

HI + SO2 forms …

Answer 13

H2S + 3I2 + 2H2O

Question 14

What is the test for halides?

Answer 14

Add Nitric acid (HNO3) then add silver nitrate (AgNO3)

Question 15

Why is nitric acid added?

Answer 15

To remove any unwanted ions, mainly CO3 (2-) ions

Question 16

Ag(+) + halide forms

Answer 16

Aghalide e.g AgCl

Question 17

What happens when Ag(+) reacts with Cl-

Answer 17

white precipitate

Question 18

What happens when Ag(+) reacts with Br-

Answer 18

cream precipitate

Question 19

What happens when Ag(+) reacts with I-

Answer 19

yellow precipitate

Question 20

What can be used to further prove the presence of each halide?

Answer 20

Ammonia (NH3)

Question 21

What does AgCl dissolve in?

Answer 21

Dilute NH3

Question 22

What does AgBr dissolve in?

Answer 22

Conc NH3

Question 23

What does AgBr dissolve in?

Answer 23

Doesn’t dissolve in NH3

Question 24

Why is HCl not used instead of HNO3?

Answer 24

Contains chloride ions, would give white precipitate every time, invalidating result

Question 25

What is a disproportionation reaction?

Answer 25

One where a substance is both oxidised and reduced

Question 26

Cl2 (g) + 2NaOH (aq) (cold,dilute,aqueous) (reversible reaction)

Answer 26

NaClO (aq) + NaCl (aq) + H2O (l) NaClO = bleach

Question 27

What is bleach used for?

Answer 27

Killing bacteria Bleaching paper Treating water

Question 28

Cl2 + H2O forms (reversible reaction)

Answer 28

2H(+) + Cl(-) + ClO(-)

Question 29

What are chlorate ions used for?

Answer 29

Killing bacteria in water

Question 30

What are the advantages of adding chlorine to water?

Answer 30

Can be used to kill bacteria and pathogens Inhibits algal growth Prevents reinfection of water downstream

Question 31

What are the disadvantages of adding chlorine to water?

Answer 31

Its a toxic and harmful gas, irritates the respiratory system Forms chlorinated hydrocarbons such as chloromethane