Chemistry - Equations

Question 1

Action of Metals with Alkalis

Answer 1

Metal + Alkali → Salt + Hydrogen

Question 2

Reaction of Zinc with Alkali

Answer 2

Zn + 2KOH → K₂ZnO₂ + H₂

Question 3

Reaction of Aluminum with Alkali

Answer 3

2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂

Question 4

Reaction of Lead with Alkali

Answer 4

Pb + 2NaOH → Na₂PbO₂ + H₂

Question 5

Reaction of Metal Oxides / Hydroxides with Alkalis

Answer 5

Metal oxide / Hydroxide + Alkali → Salt + Water

Question 6

Reaction of ZnO with Alkali

Answer 6

ZnO + 2KOH → K₂ZnO₂ + H₂O

Question 7

Reaction of PbO with Alkali

Answer 7

PbO + 2NaOH → Na₂PbO₂ + H₂O

Question 8

Reaction of Al₂O₃ with Alkali

Answer 8

Al₂O₃ + 2NaOH → 2NaAlO₂ + 2H₂O

Question 9

Reaction of Pb(OH)₂ with Alkali

Answer 9

Pb(OH)₂ + 2NaOH → Na₂PbO₂ + 2H₂O

Question 10

Reaction of Al(OH)₃ with Alkali

Answer 10

Al(OH)₃ + NaOH → NaAlO₂ + 2H₂O

Question 11

Electrolysis of Molten Lead Bromide

Answer 11

Occurs with graphite electrodes at molten state (above 380°C)

Question 12

Electrolyte used in Electrolysis of PbBr₂

Answer 12

Electrolysis of molten lead bromide with graphite electrodes
(molten state above 380°C)
PbBr2 → Pb2+ + 2Br−
Reaction at anode [graphite]
2Br− → 2e− → Br2
Br + Br → Br2 (brown)
Reaction at cathode [graphite]
Pb2+ + 2e− → Pb

Question 13

Reaction at Anode in PbBr₂ Electrolysis

Answer 13

2Br⁻ → 2e⁻ + Br₂ (brown gas)

Question 14

Reaction at Cathode in PbBr₂ Electrolysis

Answer 14

Pb²⁺ + 2e⁻ → Pb (lead metal)

Question 15

Electrolysis of Acidified Water

Answer 15

Uses platinum electrodes

Question 16

Reaction at Anode in Electrolysis of Water

Answer 16

4OH⁻ − 4e⁻ → 2H₂O + O₂ (gas)

Question 17

Reaction at Cathode in Electrolysis of Water

Answer 17

4H⁺ + 4e⁻ → 2H₂ (gas)

Question 19

Electrolysis of Aqueous CuSO₄

Answer 19

Uses copper electrodes

Question 20

Reaction at Anode in Electrolysis of CuSO₄

Answer 20

Cu → Cu²⁺ + 2e⁻

Question 21

Reaction at Cathode in Electrolysis of CuSO₄

Answer 21

Cu²⁺ + 2e⁻ → Cu

Question 22

Application of Electrolysis: Electroplating

Answer 22

Used for coating metals with a thin layer of another metal

Question 23

Electrolyte used in Silver Plating

Answer 23

Na[Ag(CN)₂]

Question 24

Reaction at Anode in Silver Plating

Answer 24

Ag → Ag⁺ + e⁻

Question 25

Reaction at Cathode in Silver Plating

Answer 25

Ag⁺ + e⁻ → Ag (silver coating)

Question 27

Electrolyte used in Nickel Plating

Answer 27

Aqueous NiSO₄

Question 28

Reaction at Anode in Nickel Plating

Answer 28

Ni → Ni²⁺ + 2e⁻

Question 29

Reaction at Cathode in Nickel Plating

Answer 29

Ni²⁺ + 2e⁻ → Ni (nickel coating)

Question 30

Application of Electrolysis: Electro-Refining of Copper

Answer 30

Used to purify copper

Question 31

Electrolyte used in Copper Refining

Answer 31

Aqueous CuSO₄

Question 32

Reactions in Electro-Refining of Copper

Answer 32

CuSO₄ → Cu²⁺ + SO₄²⁻ and H₂O → H⁺ + OH⁻

Question 33

Reaction at Anode in Copper Refining

Answer 33

Cu → Cu²⁺ + 2e⁻

Question 34

Reaction at Cathode in Copper Refining

Answer 34

Cu²⁺ + 2e⁻ → Cu (pure copper deposited)