1. Which of the following is not a physical change?
(a) Boiling of water to give water vapour
(b) Melting of ice to give water
(c) Dissolution of salt in water
(d) Combustion of Liquefied Petroleum Gas (LPG)
1. Which of the following is not a physical change?
(a) Boiling of water to give water vapour
(b) Melting of ice to give water
(c) Dissolution of salt in water
(d) Combustion of Liquefied Petroleum Gas (LPG)
Explanation:
(d) Combustion of Liquefied Petroleum Gas (LPG)
2. The following reaction is an example of a
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(i) displacement reaction (ii) combination reaction
(iii) redox reaction (iv) neutralisation reaction
(a) (i) and (iv) (b) (ii) and (iii)
(c) (i) and (iii) (d) (iii) and (iv
2. The following reaction is an example of a
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(i) displacement reaction (ii) combination reaction
(iii) redox reaction (iv) neutralisation reaction
(a) (i) and (iv) (b) (ii) and (iii)
(c) (i) and (iii) (d) (iii) and (iv
Explanation:
(c) Displacement Reaction and Redox Reaction
3. Which of the following statements about the given reaction are correct?
3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2(g)
(i) Iron metal is getting oxidised (ii) Water is getting reduced
(iii) Water is acting as reducing agent (iv) Water is acting as oxidising agent
(a) (i), (ii) and (iii) (b) (iii) and (iv)
(c) (i), (ii) and (iv) (d) (ii) and (iv)
3. Which of the following statements about the given reaction are correct?
3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2(g)
(i) Iron metal is getting oxidised (ii) Water is getting reduced
(iii) Water is acting as reducing agent (iv) Water is acting as oxidising agent
(a) (i), (ii) and (iii) (b) (iii) and (iv)
(c) (i), (ii) and (iv) (d) (ii) and (iv)
Explanation:
(c) Iron metal is getting oxidised , Water is getting reduced and Water is acting as oxidising agent.
4. Which of the following are exothermic processes?
(i) Reaction of water with quick lime (ii) Dilution of an acid
(iii) Evaporation of water (iv) Sublimation of camphor (crystals)
(a) (i) and (ii) (b) (ii) and (iii)
(c) (i) and (iv) (d) (iii) and (iv)
4. Which of the following are exothermic processes?
(i) Reaction of water with quick lime (ii) Dilution of an acid
(iii) Evaporation of water (iv) Sublimation of camphor (crystals)
(a) (i) and (ii) (b) (ii) and (iii)
(c) (i) and (iv) (d) (iii) and (iv)
Explanation:
(a) Reaction of water with quick lime And Dilution of an acid
5. Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct?
(i) In beakers A and B, exothermic process has occurred.
(ii) In beakers A and B, endothermic process has occurred.
(iii) In beaker C exothermic process has occurred.
(iv) In beaker C endothermic process has occurred.
(a) (i) only (b) (ii) only
(c) (i) and (iv) (d) (ii) and (iii)
5. Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct?
(i) In beakers A and B, exothermic process has occurred.
(ii) In beakers A and B, endothermic process has occurred.
(iii) In beaker C exothermic process has occurred.
(iv) In beaker C endothermic process has occurred.
(a) (i) only (b) (ii) only
(c) (i) and (iv) (d) (ii) and (iii)
Explanation:
(c)
6. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?
(a) KMnO4 is an oxidising agent, it oxidises FeSO4
(b) FeSO4 acts as an oxidising agent and oxidises KMnO4
(c) The colour disappears due to dilution; no reaction is involved
(d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.
6. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?
(a) KMnO4 is an oxidising agent, it oxidises FeSO4
(b) FeSO4 acts as an oxidising agent and oxidises KMnO4
(c) The colour disappears due to dilution; no reaction is involved
(d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.
Explanation:
(a) KMno4 is an oxidising agent, it oxidises FeSO4
7. Which among the following is(are) double displacement reaction(s)?
(i) Pb + CuCl2 → PbCl2+ Cu
(ii) Na2SO4+ BaCl2 → BaSO4+ 2NaCl
(iii) C + O2 → CO2
(iv) CH4+ 2O2 → CO2+ 2H2O
(a) (i) and (iv) (b) (ii) only
(c) (i) and (ii) (d) (iii) and (iv)
7. Which among the following is(are) double displacement reaction(s)?
(i) Pb + CuCl2 → PbCl2+ Cu
(ii) Na2SO4+ BaCl2 → BaSO4+ 2NaCl
(iii) C + O2 → CO2
(iv) CH4+ 2O2 → CO2+ 2H2O
(a) (i) and (iv) (b) (ii) only
(c) (i) and (ii) (d) (iii) and (iv)
Explanation:
(b) (iii) and (iv)
8. Which among the following statement(s) is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to
(i) the formation of silver by decomposition of silver chloride
(ii) sublimation of silver chloride
(iii) decomposition of chlorine gas from silver chloride
(iv) oxidation of silver chloride
(a) (i) only (b) (i) and (iii)
(c) (ii) and (iii) (d) (iv) only
8. Which among the following statement(s) is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to
(i) the formation of silver by decomposition of silver chloride
(ii) sublimation of silver chloride
(iii) decomposition of chlorine gas from silver chloride
(iv) oxidation of silver chloride
(a) (i) only (b) (i) and (iii)
(c) (ii) and (iii) (d) (iv) only
Explanation:
(a) (i) only
9. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?
(i) It is an endothermic reaction
(ii) It is an exothermic reaction
(iii) The pH of the resulting solution will be more than seven
(iv) The pH of the resulting solution will be less than seven
(a) (i) and (ii) (b) (ii) and (iii)
(c) (i) and (iv) (d) (iii) and (iv)
9. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?
(i) It is an endothermic reaction
(ii) It is an exothermic reaction
(iii) The pH of the resulting solution will be more than seven
(iv) The pH of the resulting solution will be less than seven
(a) (i) and (ii) (b) (ii) and (iii)
(c) (i) and (iv) (d) (iii) and (iv)
Explanation:
(b) (ii) and (iii)
10. Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
(i) Displacement reaction
(ii) Precipitation reaction
(iii) Combination reaction
(iv) Double displacement reaction
(a) (i) only (b) (ii) only
(c) (iv) only (d) (ii) and (iv)
10. Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
(i) Displacement reaction
(ii) Precipitation reaction
(iii) Combination reaction
(iv) Double displacement reaction
(a) (i) only (b) (ii) only
(c) (iv) only (d) (ii) and (iv)
Explanation:
(d) (ii) and (iv)
11. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is
(a) 1:1
(b) 2:1
(c) 4:1
(d) 1:2
11. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is
(a) 1:1
(b) 2:1
(c) 4:1
(d) 1:2
Explanation:
(b) 2:1
12. Which of the following is(are) an endothermic process(es)?
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water
(a) (i) and (iii) (b) (ii) only
(c) (iii) only (d) (ii) and (iv)
12. Which of the following is(are) an endothermic process(es)?
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water
(a) (i) and (iii) (b) (ii) only
(c) (iii) only (d) (ii) and (iv)
Explanation:
(d) (ii) and (iv)
13. In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?
(a) Lead sulphate (insoluble)
(b) Lead acetate
(c) Ammonium nitrate
(d) Potassium sulphate
13. In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?
(a) Lead sulphate (insoluble)
(b) Lead acetate
(c) Ammonium nitrate
(d) Potassium sulphate
Explanation:
(b) Lead acetate
14. Which of the following gases can be used for storage of fresh sample of an oil for a long time?
(a) Carbon dioxide or oxygen
(b) Nitrogen or oxygen
(c) Carbon dioxide or helium
(d) Helium or nitrogen
14. Which of the following gases can be used for storage of fresh sample of an oil for a long time?
(a) Carbon dioxide or oxygen
(b) Nitrogen or oxygen
(c) Carbon dioxide or helium
(d) Helium or nitrogen
Explanation:
(d) Helium or nitrogen
15. The following reaction is used for the preparation of oxygen gas in the laboratory.
2KClO3 (s) Heat → Catalyst 2KCl (s) + 3O2 (g)
Which of the following statement(s) is(are) correct about the reaction?
(a) It is a decomposition reaction and endothermic in nature
(b) It is a combination reaction
(c) It is a decomposition reaction and accompanied by release of heat
(d) It is a photochemical decomposition reaction and exothermic in nature.
15. The following reaction is used for the preparation of oxygen gas in the laboratory.
2KClO3 (s) Heat → Catalyst 2KCl (s) + 3O2 (g)
Which of the following statement(s) is(are) correct about the reaction?
(a) It is a decomposition reaction and endothermic in nature
(b) It is a combination reaction
(c) It is a decomposition reaction and accompanied by release of heat
(d) It is a photochemical decomposition reaction and exothermic in nature.
Explanation:
(a) It is a decomposition reaction and accompanied by release of heat.
16. Which one of the following processes involve chemical reactions?
(a) Storing of oxygen gas under pressure in a gas cylinder
(b) Liquefaction of air
(c) Keeping petrol in a china dish in the open
(d) Heating copper wire in presence of air at high temperature.
16. Which one of the following processes involve chemical reactions?
(a) Storing of oxygen gas under pressure in a gas cylinder
(b) Liquefaction of air
(c) Keeping petrol in a china dish in the open
(d) Heating copper wire in presence of air at high temperature.
Explanation:
(d) Heating copper wire in presence of air at high temperature.
17. In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
(a) 2H2(l) + O2(l) → 2H2O(g)
(b) 2H2(g) + O2(l) → 2H2O(l)
(c) 2H2(g) + O2(g) → 2H2O(l)
(d) 2H2(g) + O2(g) → 2H2O(g)
17. In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
(a) 2H2(l) + O2(l) → 2H2O(g)
(b) 2H2(g) + O2(l) → 2H2O(l)
(c) 2H2(g) + O2(g) → 2H2O(l)
(d) 2H2(g) + O2(g) → 2H2O(g)
Explanation:
(d) 2H2(g) + O2(g) → 2H2O(g)
18. Which of the following are combination reactions?
(i) 2KClO3→ Heat 2KCl + 3O2
(ii) MgO + H2O → Mg(OH)2
(iii) 4Al + 3O2→ 2Al2 O
(iv) Zn + FeSO4→ ZnSO4+ Fe
(a) (i) and (iii) (b) (iii) and (iv)
(c) (ii) and (iv) (d) (ii) and (iii)
18. Which of the following are combination reactions?
(i) 2KClO3→ Heat 2KCl + 3O2
(ii) MgO + H2O → Mg(OH)2
(iii) 4Al + 3O2→ 2Al2 O
(iv) Zn + FeSO4→ ZnSO4+ Fe
(a) (i) and (iii) (b) (iii) and (iv)
(c) (ii) and (iv) (d) (ii) and (iii)
Explanation:
(d) (ii) and (iii)
19. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.
(b) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.
(c) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2SO4?(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
19. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.
(b) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.
(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
Explanation:
(a) 2(g) + 3H2(g) Catalyst773 K → 2NH3(g)
This Reaction shows it is a Combination reaction.
This Reaction shows it is a Double displacement reaction
This Reaction shows it is a Double displacement reaction.
This Reaction shows it is a Redox reaction/Combustion reaction
20. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide ?
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.
20. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide ?
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.
Explanation:
(a) Fe2O3(s) + 2Al(s) → Al2O3(s) + 2Fe(l) + Heat
This Reaction shows it is a Displacement reaction/Redox reaction
(b) 3Mg(s) + N2(g) → Mg3N2(s)
This Reaction shows it is a Combination reaction
(c) 2KI(aq) +Cl2(g) → 2KCl(aq) + I2(s)
This Reaction shows it is a Displacement reaction.
This Reaction shows it is a Redox reaction/Combustion reaction.
21. Complete the missing components/variables given as x and y in the following reactions
(a) Pb(NO3)2(aq) + 2KI(aq) → PbI2(x) + 2KNO3(y)
(b) Cu(s) + 2Ag NO3(aq)→ Cu(NO3)2(aq) + x(s)
(c) Zn(s) + H2SO4(aq) → ZnSO4(x) + H2(y)
(d) CaCO3(s) →x CaO(s) + CO2(g)
21. Complete the missing components/variables given as x and y in the following reactions
(a) Pb(NO3)2(aq) + 2KI(aq) → PbI2(x) + 2KNO3(y)
(b) Cu(s) + 2Ag NO3(aq)→ Cu(NO3)2(aq) + x(s)
(c) Zn(s) + H2SO4(aq) → ZnSO4(x) + H2(y)
(d) CaCO3(s) →x CaO(s) + CO2(g)
Explanation:
(A) x → (s)
y→ (aq)
y → (g)
22. Which among the following changes are exothermic or endothermic in nature?
(a) Decomposition of ferrous sulphate
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
(d) Dissolution of ammonium chloride in water
22. Which among the following changes are exothermic or endothermic in nature?
(a) Decomposition of ferrous sulphate
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
(d) Dissolution of ammonium chloride in water
Explanation:
Dilution of sulphuric acid And Dilution of sodium hydroxide in water are exothermic as heat is released in these changes.
Decomposition of ferrous sulphate And Dissolution of ammonium chloride in water are endothermic as heat is released in these changes.
23. Identify the reducing agent in the following reactions
(a) 4NH3+ 5O2→ 4NO + 6H2O
(b) H2O + F2→ HF + HOF
(c) Fe2O3+ 3CO → 2Fe + 3CO2
(d) 2H2+ O2 → 2H2O
23. Identify the reducing agent in the following reactions
(a) 4NH3+ 5O2→ 4NO + 6H2O
(b) H2O + F2→ HF + HOF
(c) Fe2O3+ 3CO → 2Fe + 3CO2
(d) 2H2+ O2 → 2H2O
Explanation:
(A) Ammonia (NH3)
24. Identify the oxidising agent (oxidant) in the following reactions
(a) Pb3O4+ 8HCl → 3PbCl2+ Cl2+ 4H2O
(b) 2Mg + O2 → 2MgO
(c) CuSO4+ Zn → Cu + ZnSO4
(d) V2O5+ 5Ca → 2V + 5CaO
(e) 3Fe + 4H2O → Fe3O4+ 4H2
(f) CuO + H2 → Cu + H2O
24. Identify the oxidising agent (oxidant) in the following reactions
(a) Pb3O4+ 8HCl → 3PbCl2+ Cl2+ 4H2O
(b) 2Mg + O2 → 2MgO
(c) CuSO4+ Zn → Cu + ZnSO4
(d) V2O5+ 5Ca → 2V + 5CaO
(e) 3Fe + 4H2O → Fe3O4+ 4H2
(f) CuO + H2 → Cu + H2O
Explanation:
(A) Pb3O4
25. Write the balanced chemical equations for the following reactions
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2I2), liberates iodine gas and also forms potassium sulphate.
25. Write the balanced chemical equations for the following reactions
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2I2), liberates iodine gas and also forms potassium sulphate.
Explanation:
(A) Na2CO3 + HCl → NaCl + NaHCO3
26. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction?
26. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction?
Explanation:
KCl (aq) + AgNO3(aq) → AgCl (s) + KNO3(aq)
This Reaction shows that it is a double displacement reaction and Precipitation reaction.
27. Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction ?
27. Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction ?
Explanation:
2FeSO4(s) → Heat Fe2O3(s) + SO2(g) + SO3(g)
This Reaction shows that it is a thermal decomposition reaction.
28. Why do fire flies glow at night?
28. Why do fire flies glow at night?
Explanation:
Fire flies have a protein which in the presence of an enzyme undergoes aerial oxidation. This is a chemical reaction which involves emission of visible light. Therefore, fire flies glow at night.
29. Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?
29. Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?
Explanation:
Grapes when attached to the plants are living and therefore their own immune system prevents fermentation. The microbes can grow in the plucked grapes and under anaerobic conditions these can be fermented. This is a chemical change.
30. Which among the following are physical or chemical changes?
(a) Evaporation of petrol
(b) Burning of Liquefied Petroleum Gas (LPG)
(c) Heating of an iron rod to red hot.
(d) Curdling of milk
(e) Sublimation of solid ammonium chloride
30. Which among the following are physical or chemical changes?
(a) Evaporation of petrol
(b) Burning of Liquefied Petroleum Gas (LPG)
(c) Heating of an iron rod to red hot.
(d) Curdling of milk
(e) Sublimation of solid ammonium chloride
Explanation:
Physical Change
(a) Evaporation of petrol
(c) Heating of an iron rod to red hot
(e) Sublimation of solid ammonium chloride
Chamical Change:
(b) Burning of Liquefied Petroleum Gas (LPG)
(d) Curdling of Milk
31. During the reaction of some metals with dilute hydrochloric acid, following observations were made.
(a) Silver metal does not show any change
(b) The temperature of the reaction mixture rises when aluminium (Al) is added.
(c) The reaction of sodium metal is found to be highly explosive
(d) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
31. During the reaction of some metals with dilute hydrochloric acid, following observations were made.
(a) Silver metal does not show any change
(b) The temperature of the reaction mixture rises when aluminium (Al) is added.
(c) The reaction of sodium metal is found to be highly explosive
(d) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
Explanation:
(A) Silver metal does not react with dilute HCl
is added because it is an exothermic reaction.
Pb + 2HCl → PbCl2 + H2
32. A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.
32. A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.
Explanation:
Calcium oxide
CaO(s) + H2O(l) → Ca(OH)2(aq)
33. Write a balanced chemical equation for each of the following reactions and also classify them.
(a) Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.
(c) Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.
(d) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water
33. Write a balanced chemical equation for each of the following reactions and also classify them.
(a) Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.
(c) Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.
(d) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water
Explanation:
(A) Pb(CH3COO)2 + 2HCl → PbCl2 + CH3COOH, This reaction shows that it is a Double displacement reaction.
(B) 2Na + 2C2H5OH → 2C2H5ONa + H2 This reaction shows that it is a Displacement reaction
34. Why do we store silver chloride in dark coloured bottles?
34. Why do we store silver chloride in dark coloured bottles?
Explanation:
Silver chloride on exposure to sunlight may decompose as per the following rection.
2AgCl → 2Ag + Cl2
Therefore, it is stored in dark coloured bottles.
35. Balance the following chemical equations and identify the type of chemical reaction.
(a) Mg(s) + Cl2(g) → MgCl2(s)
(b) HgO(s) → Heat Hg(l) + O2(g)
(c) Na(s) + S(s)→ Fuse Na2S(s)
(d) TiCl4(l) + MgTiCl4
(e) CaO(s) + SiO2(s)→ CaSiO3(s)
(f) H2O2(l) → U V H2O(l) + O2(g)
35. Balance the following chemical equations and identify the type of chemical reaction.
(a) Mg(s) + Cl2(g) → MgCl2(s)
(b) HgO(s) → Heat Hg(l) + O2(g)
(c) Na(s) + S(s)→ Fuse Na2S(s)
(d) TiCl4(l) + MgTiCl4
(e) CaO(s) + SiO2(s)→ CaSiO3(s)
(f) H2O2(l) → U V H2O(l) + O2(g)
Explanation:
(A) Balanced; Combination reaction
36. A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.
(a) Write the chemical formulae of X and Y.
(b) Write a balanced chemical equation, when X is dissolved in water.
36. A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.
(a) Write the chemical formulae of X and Y.
(b) Write a balanced chemical equation, when X is dissolved in water.
Explanation:
(A) 2Mg + O2 → 2MgO
3Mg + N2 → Mg3N2
X is MgO; Y is Mg3N2
37. Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why?
37. Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why?
Explanation:
Zinc is above hydrogen whereas copper is below hydrogen in the activity series of metals. That is why zinc displaces hydrogen from dilute hydrochloric acid, while copper does not.
Zn + HCl → ZnCl2 + H2Cu + HCl → No reaction
38. A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
(a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved
(b) Name the black substance formed and give its chemical formula?
38. A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
(a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved
(b) Name the black substance formed and give its chemical formula?
Explanation:
(A) Metals such as silver when attacked by substances around it such as moisture, acids, gases etc, are said to corrode and this phenomenon is called corrosion.
(b) The black substance is formed because silver (Ag) reacts with H2S present in air. It forms thin black coating of silver sulphide (Ag2S).
39. On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed
(a) Write a balanced chemical equation of the reaction.
(b) Identity the brown gas X evolved.
(c) Identity the type of reaction.
(d) What could be the pH range of aqueous solution of the gas X?
39. On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed
(a) Write a balanced chemical equation of the reaction.
(b) Identity the brown gas X evolved.
(c) Identity the type of reaction.
(d) What could be the pH range of aqueous solution of the gas X?
Explanation:
(A) Balanced chemical equation 2Cu(NO3)2 (s)→ Heat 2CuO (s) + O2(g) + 4NO2(g)
40. Give the characteristic tests for the following gases
(a) CO2
(b) SO2
(c) O2
(d) H2
40. Give the characteristic tests for the following gases
(a) CO2
(b) SO2
(c) O2
(d) H2
Explanation:
(a) Carbon dioxide (CO2) gas turns lime water milky when passed through it due to the formation of insoluble calcium carbonate.
Ca(OH)2 + CO2 → CaCO3+ H2O
(Lime water) (Carbon dioxide) (Calcium Carbonate)
41. What happens when a piece of
(a) zinc metal is added to copper sulphate solution?
(b) aluminium metal is added to dilute hydrochloric acid?
(c) silver metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs?
41. What happens when a piece of
(a) zinc metal is added to copper sulphate solution?
(b) aluminium metal is added to dilute hydrochloric acid?
(c) silver metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs?
Explanation:
(a) Zinc being more reactive than copper displaces copper from its solution and a solution of zinc sulphate is obtained,
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
2Al(s) + 6HCl (aq) → 2AlCl3(aq) + 3H2(g)
Ag (s) + CuSO4(aq) → No reaction
42. What happens when zinc granules are treated with dilute solution of H2SO4, HCl, HNO3, NaCl and NaOH, also write the chemical equations if reaction occurs.
42. What happens when zinc granules are treated with dilute solution of H2SO4, HCl, HNO3, NaCl and NaOH, also write the chemical equations if reaction occurs.
Explanation:
(a) Dilute H2SO4
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
(b) Dilute HCl
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
(c) Dilute HNO3
Reaction with dilute HNO3 is different as compared to other acids because nitric acid is an oxidising agent and it oxidisesH2 gas evolved to H2O.
4 Zn(s) + 10HNO3(aq) → 4 Zn(NO3)2 (aq) + 5 H2O(l) + N2O(g)
(d) NaCl solution
Zn(s) + NaCl (aq) → No reaction
(e) NaOH solution
Zn(s) + 2 NaOH (aq) → Na2 ZnO2 (aq) + H2(g)
43. On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.
(a) Write a balanced chemical equation of the reaction involved?
(b) What other name can be given to this precipitation reaction?
(c) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?
43. On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.
(a) Write a balanced chemical equation of the reaction involved?
(b) What other name can be given to this precipitation reaction?
(c) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?
Explanation:
(A) Balanced chemical equation
Na2SO3(aq) + BaCl2(aq) → BaSO3(s) + 2 NaCl (aq)
such as HCl decomposes barium sulphite to produce sulphur dioxide gas which has the smell of burning sulphur.
BaSO3(s) + 2HCl (aq) → BaCl2+ H2O + SO2(g)
44. You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO3, ZnCl2 and H2O. In which of the above containers these solutions can be kept?
44. You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO3, ZnCl2 and H2O. In which of the above containers these solutions can be kept?
Explanation:
(a) Dilute HCl
Copper does not react with dilute HCl. Therefore, it can be kept
(b) Dilute HNO3
Nitric acid acts as a strong oxidising agent and reacts with copper vessel, therefore cannot be kept.
(c) ZnCl2
Zinc is more reactive than copper (Cu) therefore, no displacement reaction occurs and hence can be kept.
(d) H2O
Copper does not react with water. Therefore, can be kept.
