COMPLETE
REVISION
, CHEMICAL REACTION AND EQUATION
Q. Balance the following chemical equations and determine the values of A, B, C , D and E in each case:
(i) A MnO₂ + B HCl → C MnCl₂ + D H₂O + E Cl₂
(ii) A NaOH + B Al₂O₃→ C NaAlO₂ + D H₂O X
(iii) A Al + B H₂O → C Al₂O₃ + D H₂
→
(iv) A Pb(NO₃)₂ —heat B PbO + C NO₂ + D O₂
(v) CH₄ + AO₂ → CO₂ + BH₂O + Heat
Y
(i) MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
A = 1, B = 4, C = 1, D = 2, E = 1
(ii) 2NaOH + Al₂O₃ → 2NaAlO₂ + H₂O
A = 2, B = 1, C = 2, D = 1
→
(iii) 2Al + 3H₂O Al₂O₃ + 3H₂
A = 2, B = 3, C = 1, D = 3
(iv) 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂
A = 2, B = 2, C = 4, D = 1
(v) A = 2, B = 2
, CHEMICAL REACTION AND EQUATION
Q. A shiny metal ribbon ‘X’ burns in oxygen with a dazzling white flame
and forms a white ash ‘Y’. A student collects the product in a wet watch
X
glass.
(a) Identify ‘X’ and ‘Y’.
(b) Write the balanced chemical equation for the reaction.
Y
(c) Name the type of reaction involved.
(d) Does metal ‘X’ undergo oxidation or reduction in this reaction?
Justify your answer.
(e) If the product formed after burning is collected in a wet watch glass,
what new compound may be formed?
Ans. (a) X = Magnesium (Mg), Y = Magnesium oxide (MgO) (white ash)
(b) Balanced equation:
2Mg(s) + O₂(g)→ 2MgO(s)
(c) Type of reaction: Combination reaction (also oxidation/combustion)
(d) Mg undergoes oxidation because Mg combines with oxygen / gains oxygen to form MgO.
(e) In a wet watch glass, MgO reacts with water to form magnesium hydroxide:
MgO(s) + H₂O(l) → Mg(OH)₂
, CHEMICAL REACTION AND EQUATION
Q. (a) What happens when copper is heated in air?
(b) What happens when lead nitrate is heated?
(c) What happens when ferrous sulphate is heated? X
(d) What happens when quicklime (CaO) reacts with water?
For each reaction, answer the following:
Write the balanced chemical equation. Y
Name the type of reaction.
What are the observations during the reaction?
(a) Balanced chemical equation: 2Cu + O₂ → 2CuO (Combination and oxidation reaction)
Observations: Reddish-brown copper turns black due to formation of copper(II) oxide.
(b) Balanced chemical equation: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂ (Thermal decomposition reaction)
Observations: Brown fumes of NO₂ are evolved and yellow PbO residue remains.
(c)Balanced chemical equation: 2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ (Thermal decomposition reaction)
Observations: Green crystals turn brown and pungent gases are evolved.
(d) Balanced chemical equation: CaO + H₂O → Ca(OH)₂ + Heat (Combination and exothermic reaction.)
Observations: Heat is produced and white slaked lime is formed.
REVISION
, CHEMICAL REACTION AND EQUATION
Q. Balance the following chemical equations and determine the values of A, B, C , D and E in each case:
(i) A MnO₂ + B HCl → C MnCl₂ + D H₂O + E Cl₂
(ii) A NaOH + B Al₂O₃→ C NaAlO₂ + D H₂O X
(iii) A Al + B H₂O → C Al₂O₃ + D H₂
→
(iv) A Pb(NO₃)₂ —heat B PbO + C NO₂ + D O₂
(v) CH₄ + AO₂ → CO₂ + BH₂O + Heat
Y
(i) MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
A = 1, B = 4, C = 1, D = 2, E = 1
(ii) 2NaOH + Al₂O₃ → 2NaAlO₂ + H₂O
A = 2, B = 1, C = 2, D = 1
→
(iii) 2Al + 3H₂O Al₂O₃ + 3H₂
A = 2, B = 3, C = 1, D = 3
(iv) 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂
A = 2, B = 2, C = 4, D = 1
(v) A = 2, B = 2
, CHEMICAL REACTION AND EQUATION
Q. A shiny metal ribbon ‘X’ burns in oxygen with a dazzling white flame
and forms a white ash ‘Y’. A student collects the product in a wet watch
X
glass.
(a) Identify ‘X’ and ‘Y’.
(b) Write the balanced chemical equation for the reaction.
Y
(c) Name the type of reaction involved.
(d) Does metal ‘X’ undergo oxidation or reduction in this reaction?
Justify your answer.
(e) If the product formed after burning is collected in a wet watch glass,
what new compound may be formed?
Ans. (a) X = Magnesium (Mg), Y = Magnesium oxide (MgO) (white ash)
(b) Balanced equation:
2Mg(s) + O₂(g)→ 2MgO(s)
(c) Type of reaction: Combination reaction (also oxidation/combustion)
(d) Mg undergoes oxidation because Mg combines with oxygen / gains oxygen to form MgO.
(e) In a wet watch glass, MgO reacts with water to form magnesium hydroxide:
MgO(s) + H₂O(l) → Mg(OH)₂
, CHEMICAL REACTION AND EQUATION
Q. (a) What happens when copper is heated in air?
(b) What happens when lead nitrate is heated?
(c) What happens when ferrous sulphate is heated? X
(d) What happens when quicklime (CaO) reacts with water?
For each reaction, answer the following:
Write the balanced chemical equation. Y
Name the type of reaction.
What are the observations during the reaction?
(a) Balanced chemical equation: 2Cu + O₂ → 2CuO (Combination and oxidation reaction)
Observations: Reddish-brown copper turns black due to formation of copper(II) oxide.
(b) Balanced chemical equation: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂ (Thermal decomposition reaction)
Observations: Brown fumes of NO₂ are evolved and yellow PbO residue remains.
(c)Balanced chemical equation: 2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ (Thermal decomposition reaction)
Observations: Green crystals turn brown and pungent gases are evolved.
(d) Balanced chemical equation: CaO + H₂O → Ca(OH)₂ + Heat (Combination and exothermic reaction.)
Observations: Heat is produced and white slaked lime is formed.
