Halogen (group 7) 10

Question 1

physical properties

Answer 1

fluorine = pale yellow gas
chlorine = greenish gas
bromine = red-brown liquid
iodine = black solid

Question 2

the size of atoms

Answer 2

bigger down the group

Question 3

electronegativity

Answer 3

measure of the ability of an atom to attract electrons within a covalent bond

decreases down the group

depends on- distance between nucleus and electron
nuclear charge
shielding effect from inner electrons

Question 4

which element is the most electronegative

Answer 4

fluorine

Question 5

Melting and boiling point

Answer 5

Increase down the group

Larger atoms have more electrons and this means that the van der walls forces between molecules stronger

Question 6

Trend in oxidising ability

Answer 6

Oxidising ability of the halogens increases going up the group
(The trend in oxidising ability of the halogens down the group, including displacement reactions of halide ions in aqueous solution)

Question 7

Displacement reaction

Answer 7

The halide in the compound will be displaced by a more reactive halide

Fluorine would displace chlorine, bromine and iodine
Chlorine would displace bromine and iodine
Bromine would displace iodine

Question 8

Halide ions as reducing agents

Answer 8

Halide ions lose electrons
Larger the ion, the more easily it loses an electron. Electron is further from the nucleus so the attraction is less

(The trend in reducing ability of the halide ions, including the reactions of solid sodium halides with concentrated sulfuric acid)

Question 9

Solid sodium chloride with concentrated sulphuric acid

Answer 9

Streamy fumes of hydrogen chlorine seen

NaCl(s) + H2SO4(l) —– NaHSO4(s) + HCl(g)

Not a redox reaction because no oxidation states have changed

Question 10

Solid sodium bromide and concentrated sulphuric acid

Answer 10

Steamy hydrogen bromide and brown fumes of bromine

NaBr(s) + H2SO4(l) ——- NaHSO4(s) + HCl(g)

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

Question 11

Solid sodium iodide and concentrated sulphuric acid

Answer 11

NaI(s) + H2SO4(l) —– NaHSO4(s) + HI(g)

8H+ +8I- + H2SO4 ——- H2S(g) + 4H2O(l) + 4I2(s)

Question 12

Silver fluride

Answer 12

No precipitate

Question 13

Silver chloride

Answer 13

White precipitate

Dissolve in dilute ammonia

Question 14

Silver bromide

Answer 14

Cream precipitate

Dissolved in concentrated ammonia

Question 15

Silver iodide

Answer 15

Pale yellow precipitate

Insoluble in concentrated ammonia

Question 16

Chlorine and water

Answer 16

Cl2(g) + H2O(l) —— HClO(aq) + HCl(aq)

Question 17

What is chlorine used for?

Answer 17

Purify water for drink and swimming pools
Bleach
(aslo a poisonous gas )

Question 18

Chlorine and sunlight

Answer 18

2Cl2(g) + 2H2O(g) ——- 4HCl(aq) + O2(g)

This means that chorine is lost so has to be replaced

Question 19

Alternative way

Answer 19

NaClO(s) + H2O —— Na+ + OH- +HClO(aq)

Swimming pool have to be kept slightly acidic

Question 20

Alkali and chlorine

Answer 20

Cl2(g) + 2NaOH(aq) —— NaClO(aq) + NaCl(aq) + H2O(l)

Disproportionation

Question 21

which element is the most powerful oxidising agent

Answer 21

fluorine

Question 22

Halide ion

Answer 22

loe an electron to turn into a halogen

Question 23

explain why ammonia solution is added

Answer 23

silver halide has a different solubility in ammonia

Question 24

Halogens

Answer 24

decrease down the group
boiling point increase down the group
electronegativity decreases down the group

Question 25

flame test

Answer 25

Ca2+ =brick red
Sr2+ = red
Ba2+ = pale green

Question 26

red litmus paper

Answer 26

ammonia

red to blue

Question 27

Halogenoalkane properties

Answer 27

polar bonds

substitution reactions with the nucleophiles OH–, CN– and NH3