Redox reactions in Group 7: displacement reactions

Question 1

reactions between group 1 or 2 elements with group 7 elements are most vigorous when the reactants are from the ………………of group 1 or 2 and the …………………of group 7 (top or bottom)

Answer 1

bottom of group 1 or 2 with top of group 7

Question 2

when group 1 or 2 elements react with elements in group 7, a ……………is formed which is usually …………………in colour

Answer 2

form a white ionic solid salt

Question 3

reactions between group 1 or 2 metals with a halogen involve an electron transfer to the

Answer 3

halogen

Question 4

when reacting with group 1 or group 2 metals, the halogen’s oxidation number changes from………to………………

Answer 4

0 to -1

DECREASES

Question 5

the equation for the reaction between lithium and chlorine is

Answer 5

2Li +Cl2 = 2LiCl

Question 6

halogens can displace each other if

Answer 6

the halogen added to a mixture is more reactive than the halogen in the compound

Question 7

displacement reactions for halogens occur in (conditions)

Answer 7

aqueous solution

Question 8

halogen / halide displacement reactions involve an observable……….change

Answer 8

colour change due to the reaction being carried in aqueous solution

Question 9

when carrying out halogen / halide displacement reactions, it is good to add …………………at the end to observe the colour change more clearly

Answer 9

add an organic solvent such as cyclohexane

Question 10

why is the colour change for halogen / halide displacement reactions seen more clearly when cyclohexane is added

Answer 10

halogens are more soluble in cyclohexane than in water because of the polarity of the H2O molecules. when the halogen is displaced, it then dissolved into the cyclohexane to produce the distincive colour change

Question 11

the colour change for when iodine is displaced is

Answer 11

pale orange/red to purple

Question 12

the colour change for when bromine is displaced is

Answer 12

pale yellow to orange

Question 13

the colour observed when chlorine dissolves in organic solvent is

Answer 13

pale green

Question 14

chlorine displaces……………….and………………………….
bromine displaces…………………….but not………………
iodine does not displace…………….either………………

Answer 14

chlorine displaces bromine and iodine
bromine displaces iodine but not chlorine
iodine does not displace bromine either chlorine

Question 15

two issues for interpreting colour changes for displacement reactions when water is the solvent are:

Answer 15

• some colours are similar in water (such as iodine and bromine)
• colours differ with concentration

Question 16

the equation showing the reaction between chlorine and sodium bromide is:
the ionic equation is:

Answer 16

Cl2 + 2NaBr = 2NaCl + Br2

Cl2 + 2Br- = 2Cl- + Br2

Question 17

halogen / halide displacement reactions are

a) redox
b) disproportionation
c) oxidation

reactions?

Answer 17

redox as the reacting halogen goes from 0 to -1 and the halide from -1 to 0

Question 18

chlorine is the (second) most reactive halogen because of these two factors:

Answer 18

• it is the smallest atom, so the incoming electron gets closer to and is more attracted by the protons in the nucleus
• it has the smallest number of complete energy levels of electrons, so the incoming electron experiences the least repulsion