11: Group 17 ❎

Question 1

disproportionation reaction between Cl₂ and cold NaOH

Answer 1

2NaOH + Cl₂ → NaCl + NaClO + H₂O

NaCl → -1
NaClO → +1

Question 2

disproportionation reaction between Cl₂ and hot NaOH

Answer 2

6NaOH + 3Cl₂ → 5NaCl + NaClO₃ + 3H₂O

NaCl → -1
NaClO₃ → +5

Question 3

reaction of Cl₂ with H₂O

Answer 3

Cl₂ + H₂O → HCl + HClO

Question 4

Name of HClO

Answer 4

hypochlorous acid

Question 5

Trend in colour

Answer 5

down the group, colour gets darker

Question 6

Trend in density

Answer 6

down the group, density increases

Question 7

Trend in melting and boiling point

Answer 7

Down the group, m.p. and b.p. increases

Question 8

Trend in volatility

Answer 8

down the group, volatility decreases

Question 9

Trend in bond strength

Answer 9

**bond strength decreases
**
because atomic radius increases down the group, decreasing nuclear attraction for the shared pair of electrons

Question 10

flourine appearance

Answer 10

yellow gas

Question 11

chlorine appearance

Answer 11

green gas

Question 12

bromine appearance

Answer 12

brown liquid

Question 13

iodine appearance

Answer 13

black solid/purple vapour

Question 14

explanation for trend in volatility in terms of instantaneous-dipole induced-dipole forces

Answer 14

down the group, number of electrons increase;
instanteous-dipole induced-dipole forces become stronger, requiring a larger amount of energy to overcome them,
so volatility decreases

Question 15

trend in oxidising ability of elements

Answer 15

oxidising ability decreases down the group

• down the group, shielding effect increases
• atomic radius increases and electronegativity decreases
• halogen’s ability to become reduced decreases

Question 16

trend in relative thermal stabilities of the hydrogen halides

Answer 16

thermal stability of hydrogen halides decrease down the group

Question 17

explanation for trend in thermal stability of hydrogen halides in terms of bond strengths

Answer 17

• down the group, shielding effect on the nucleus increases and ionic radius increases
• bond length increases
• less energy required to break the bond between hydrogen and halide (bond enthalpy decreases)

Question 18

trend in reactivity

Answer 18

down the group, reactivity decreases

Question 19

trend in reactivity of elements with H₂

Answer 19

down the group, reaction between H₂ and elements becomes less vigorous

Question 20

H₂ + Cl₂

Answer 20

reacts explosively with sunlight

Question 21

H₂ + F₂

Answer 21

reacts explosively even in cool, dark conditions

Question 22

H₂ + Br₂

Answer 22

reacts slowly on heating

Question 23

H₂ + I₂

Answer 23

forms an equilibrium mixture upon heating

Question 24

trend in reducing ability of halides

Answer 24

down the group, reducing ability increases

Question 25

explanation for trend in reducing ability

Answer 25

down the group, there is more shielding effect on the nucleus, and the ionic radius increases;
less nuclear attraction for the valence electrons so electrons are lost easier with less energy required

Question 26

Cl- reacting with aqueous silver ions followed by aqueous ammonia

Answer 26

white precipitate forms, soluble in dilute ammonia

Question 27

Br- reacting with aqueous silver ions followed by aqueous ammonia

Answer 27

cream precipitate forms, soluble in only concentrated ammonia

Question 28

I- reacting with aqueous silver ions followed by aqueous ammonia

Answer 28

yellow precipitate forms, insoluble in dilute and concentrated ammonia

Question 29

Cl- with concentrated sulfuric acid

Answer 29

HCl gas (white fumes) and solid NaHSO₄

H₂SO₄ (aq) + NaCl (s) → HCl (g) + NaHSO₄ (aq)

Question 30

Br- with concentrated sulfuric acid

Answer 30

HBr gas and solid NaHSO₄,

H₂SO₄ (aq) + NaBr (s) → HBr (g) + NaHSO₄ (aq)

which is turned into Br₂ gas (reddish-brown fumes), sulfur dioxide and water,
sulfuric acid is reduced to sulfur dioxide

2HBr (g) + H₂SO₄ (aq) → Br₂ (g) + SO₂ (g) + 2H₂O (l)

Question 31

I- with concentrated sulfuric acid

products

Answer 31

H₂SO₄ (aq) + XI (s) → HI (g) + XHSO₄ (aq)

Concentrated sulfuric acid is reduced to sulfur dioxide
H₂SO₄ (aq) + 2HI (s) → I₂ (g) + SO₂ (g) + 2H₂O (l)

Concentrated sulfuric acid is reduced to sulfur
H₂SO₄ (aq) + 6HI (s) → 3I₂ (g) + S (s) + 4H₂O (l)

Concentrated sulfuric acid is reduced to H₂S
8HI (g) + H₂SO₄ (aq) → 4I₂ (g) + H₂S (s) + 4H₂O (l)