Group 7

Question 1

What happens to group 7 atomic radius down the group?

Answer 1

Increases due to additional electron shells

Question 2

What happens to group 7 electronegativity down the group?

Answer 2

decreases due to increase in shielding and atomic radius. Outer shell electrons less attracted to nucleus so more easily removed

Question 3

Trend of melting and boiling point in group 7?

Answer 3

Increases - Strength of London forces due to more electrons so more energy required to overcome the bonds

Question 4

Trend of reactivity in group 7?

Answer 4

Decreases - more shielding and further distance from nucleus makes it harder to gain an electron

Question 5

What happens to the oxidising power down group 7?

Answer 5

Decreases as their inability to attract electrons decreases due to shielding and greater atomic radius

Question 6

Reactivity series of halogens?

Answer 6

F>Cl>Br>I

Question 7

Why does the reducing power of the halides increase down the group?

Answer 7

(They donate electrons to species being reduced). Increases as electrons are easier to lose from larger ions due to shielding and larger atomic radius

Question 8

Reaction of sodium chloride with H2SO4 and why? Describe any observations

Answer 8

Nacl + H2SO4 makes NaHSO4 + HCl(misty fumes) HCl cant reduce H2SO4 as they are not strong enough reducing agents.

Question 9

Reactions of sodium bromide with H2SO4 and why? Describe any observations

Answer 9

NaBr + H2SO4 makes NaHSO4 + HBr(misty fumes)
2HBr + H2SO4 makes Br2 (orange fumes) + SO2 (chocking fumes) + 2H2O
Bromide ion can reduce H2SO4 but not SO2

Question 10

Reactions of sodium iodide with H2SO4 and why? Describe any observations

Answer 10

NaI + H2SO4 makes NaHSO4 + HI(misty fumes)
2HI + H2SO4 makes I2 (grey solid) + SO2 (chocking fumes) + 2H2O
6HI + SO2 makes H2S(toxic gas and smells of bad eggs) + 3I2 + H2O
iodide ion can reduce H2SO4 and SO2

Question 11

What is chlorines reaction with cold water?

Answer 11

cl2 + H20 makes ClO- + Cl- + 2H+

Question 12

Why is chlorine used in water treatment and what is a risk?

Answer 12

• Can kill bacteria in small quantities
  -Can be toxic

Question 13

How is sodium chlorate (1) produced?

Answer 13

2NaOH(cold) + Cl2 makes NaClO + NaCl + H2O

Question 14

Reaction of chlorine with hot alkali?

Answer 14

6NaOH(hot) +3Cl2 makes NaClO3 + 5NaCl + 3H2O

Question 15

Reaction of group 7 with group one and two metals?

Answer 15

metal chloride is formed

Question 16

Observations of cl- ion with AgNO3, dil. NH3 and conc. NH3?

Answer 16

AgNO3 - white precipitate
dil. ammonia - precipitate dissolves
conc. ammonia - precipitate dissolves

Question 17

Observations of Br- ion with AgNO3, dil. NH3 and conc. NH3?

Answer 17

AgNO3 - Cream precipitate
dil. ammonia - No change
conc. ammonia - precipitate dissolves

Question 18

Observations of I- ion with AgNO3, dil. NH3 and conc. NH3?

Answer 18

AgNO3 - Yellow precipitate
dil. ammonia - No change
conc. ammonia - No change

Question 19

What happens in the reaction between ammonia and hydrogen halides?

Answer 19

forms an ammonium salt e.g. NH4Cl

Question 20

Describe reaction between hydrogen halides and water?

Answer 20

-Forms a dilute acid
- As hydrogen halides are strong acids in water they dissociate to release halide ions and hydrogen ions - hydrogen ions form a hydroxonium ion with the water molecules in solution
e.g. HCl + H2O makes Cl - + H3O+