Complete guide to "Chemical Reactions and Equations" for Chemistry students. Below you will find important questions and model answers to help you prepare.
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Which of the following is not a physical change?
Boiling of water to give water vapour
Melting of ice to give water
Dissolution of salt in water
Combustion of Liquefied Petroleum Gas (LPG)
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
(i) and (iv)
(ii) and (iii)
(i) and (iii)
(iii) and (iv)
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
(i), (ii) and (iii)
(iii) and (iv)
(i), (ii) and (iv)
(ii) and (iv)
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)
(i) and (ii)
(ii) and (iii)
(i) and (iv)
(iii) and (iv)
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.
(i) only
(ii) only
(i) and (iv)
(ii) and (iii)
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?
KMnO₄ is an oxidising agent, it oxidises FeSO₄
FeSO₄ acts as an oxidising agent and oxidises KMnO₄
The colour disappears due to dilution; no reaction is involved
KMnO₄ is an unstable compound and decomposes in the presence of FeSO₄ to a colourless compound
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
(i) and (iv)
(ii) only
(i) and (ii)
(iii) and (iv)
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
(i) only
(i) and (iii)
(ii) and (iii)
(iv) only
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
(i) and (ii)
(ii) and (iii)
(i) and (iv)
(iii) and (iv)
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
(i) only
(ii) only
(iv) only
(ii) and (iv)
Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is
1:1
2:1
4:1
1:2
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
(i) and (iii)
(ii) only
(iii) only
(ii) and (iv)
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?
Lead sulphate (insoluble)
Lead acetate
Ammonium nitrate
Potassium sulphate
Which of the following gases can be used for storage of fresh sample of an oil for a long time?
Carbon dioxide or oxygen
Nitrogen or oxygen
Carbon dioxide or helium
Helium or nitrogen
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?
It is a decomposition reaction and endothermic in nature
It is a combination reaction
It is a decomposition reaction and accompanied by release of heat
It is a photochemical decomposition reaction and exothermic in nature
Which one of the following processes involve chemical reactions?
Storing of oxygen gas under pressure in a gas cylinder
Liquefaction of air
It is a decomposition reaction and accompanied by release of heat
It is a photochemical decomposition reaction and exothermic in nature
In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
2H₂(l) + O₂(l) → 2H₂O(g)
2H₂(g) + O₂(l) → 2H₂O(l)
2H₂(g) + O₂(g) → 2H₂O(l)
2H₂(g) + O₂(g) → 2H₂O(g)
Which of the following are combination reactions? (i) 2KClO₃(s) →[heat] 2KCl(s) + 3O₂(g) (ii) MgO(s) + H₂O(l) → Mg(OH)₂(s) (iii) 4Al(s) + 3O₂(g) → 2Al₂O₃(s) (iv) Zn(s) + FeSO₄(aq) → ZnSO₄(aq) + Fe(s)
(i) and (iii)
(iii) and (iv)
(ii) and (iv)
(ii) and (iii)