Group 7: Halogens

Question 1

What is the trend in electronegativity down group 7?

Answer 1

DECREASES
bc the number of principle energy levels (shells) increases
weaker attraction to nucleus and electrons in a covalent bond

Question 2

What is the trend in boiling point down group 7?

Answer 2

INCREASES
size of atom increases
there are more VDW forces between molecules that need to be broken

Question 3

What do Halogens look like at room temperature?

Answer 3

F2 - pale yellow gas
Cl2 - pale green gas
Br2 - Dark red/orange liquid
I2 - dark purple/black solid

Question 4

What happens to a halogen’s ability to act as an oxidising agent down a group?

Answer 4

DECREASES
- atomic radius increases
- more shielding
- weaker attraction to nucleus and outer electrons so halogen gains electron less easily

Question 5

What is the observation when chlorine oxides Br- and I-

Answer 5

Br- = yellow solution is formed
I- = brown solution formed

Question 6

What is the observation when Br oxidises I-?

Answer 6

brown solution formed

Question 7

What is the ionic equation for the oxidation of Br- by Cl2

Answer 7

Cl2 + 2Br- > Br2 + 2Cl-

Question 8

What is the ionic ewuation for the oxidation of I- by Cl2?

Answer 8

Cl2 + 2I- > I2 + 2Cl-

Question 9

What is the ionic equation for the oxidation of I- by Br2

Answer 9

Br2 + 2I- > I2 + 2Br-

Question 10

What happened to the ability of a Halogen to act as a reducing agent down a group?

Answer 10

INCREASES
- size of halogen increases
- outer electron is further from nucleus
- less attraction between nucleus ant outer electron so they lose an electron easily

Question 11

How can you test the reducing ability of Halide ions?

Answer 11

an acid base reaction
by reacting solid halide salts with concentrated sulphuric acid

Question 12

What is the equation for a halide salt with sulphuric acid?

Answer 12

NaX + H2SO4 > NaHSO4 + HX

Question 13

What is the observation for HX

Answer 13

misty fumes

Question 14

What reaction does F- (NaF) undergo?

Answer 14

not a strong reducing agent so only does an acid base reaction

NaF + H2SO4 > NaH2SO4 + HF
misty fumes

Question 15

What reaction does Cl- (NaCl) undergo?

Answer 15

only undergo acid base reaction
stronger than fluorine but still not strong enough to reduce the sulphuric acid

NaCl + H2SO4 > NaH2SO4 + HCL
misty fumes

Question 16

What reactions do Br- (NaBr) undergo?

Answer 16

Both acid base reaction and redox
stronger reducing agents than Cl ions

It reduces H2SO4 to SO2

Question 17

What observations come from Br- redox reaction?

Answer 17

Choking gas - SO2
Brown gas - Br2

Question 18

What is the equation for Br- redox reaction?

Answer 18

2e- + 2H+ + H2SO4 > SO2 + 2H2O
2Br- > Br2 + 2e-

2H+ + H2SO4 + 2Br > Br2 + SO2 + 2H2O

Question 19

What reactions does I- (NaI) undergo?

Answer 19

Acid base reaction
and 3 redox rection

reduces H2SO4 to, H2S, SO2 and S

Question 20

What are the observations in each redox reaction with I-

Answer 20

SO2 - choking gas
H2S - rotten egg smell
S - yellow solid
I2 - black solid and purple gas

Question 21

How can you identify Halides in a solution?

Answer 21

using acidified silver nitrate

Question 22

What is the full and ionic equation for a Halide with silver nitrate?

Answer 22

full
AgNO3 + NaX > AgX + NaNO3

ionic
Ag+(aq) + X-(aq) > AgX

Question 23

What are the observations with Halide ions and silver nitrate?

Answer 23

AgF = NVC insoluble
AgCl = white ppt
AgBr = cream ppt
AgI = yellow ppt

Question 24

Why should Hydroxide and carbonate ions be removed before testing with Ag?

Answer 24

they both form a ppt in Ag and will interfere with the reaction

Question 25

What is the equation for removing carbonate ions using nitric acid?

Answer 25

2HNO3 + Na2CO3 > 2NaNO3 + CO2 + H2O ionic 2H+ + CO3(^2-) + H2O + CO2

Question 26

What is the trend in solubility in DILUTE NH3 down group 7?

Answer 26

decreases from AgCl to AgI AgI is insoluble

Question 27

What is the equation for AgCl in dilute NH3?

Answer 27

AgCl(s) + 2NH3(aq) > Ag(NH3)2+(aq) + Cl-

Question 28

What is the trend in solubility in CONCENTRATED NH3?

Answer 28

AgBr is soluble AgI is insoluble

Question 29

What is the equation for AgBr in concentrated NH3

Answer 29

AgBr(s) + 2NH3(aq) > Ag(NH3)2+(aq) + Br-(aq)

Question 30

What is the equation for chlorine dissolving in water?

Answer 30

Cl2(g) + H2O ⇆ HCl(aq) + HClO(aq)

Question 31

What id a disproportionatiom reaction?

Answer 31

when an atom goes through is both oxidised AND reduced

Question 32

What happened when universal indicator paper is added to chlorine water?

Answer 32

turns red first - both reaction products are acids then it turns white as HClO is an effective bleach

Question 33

What happenes when chlorine is bubbled in water in prescense of sunlight?

Answer 33

a colourless gas is produced and the green colour due to chlorine fades chlorine **oxidises water to O2**,and **chlorine is reduced to chloride**

Question 34

What is the equation for Cl and H2O in sunlight?

Answer 34

2Cl2 + 2H2O > 4HCl + O2

Question 35

What is the use of chlorine in water treatment?

Answer 35

sterilises water for swimming pools kills bacteria

Question 36

What is the equation for the reaction with Chlorine and cold dilute sodium hydroxide?

Answer 36

Cl2 + 2NaOH > H2O + NaCl + NaClO

Question 37

What is the use of NaClO?

Answer 37

active ingredient in house bleach