Chemical Reactions & Equations

Q1: The reaction of ‘magnesium’ with air is

• Exothermic reaction
• Endothermic reaction
• Reversible reaction
• Substitution reaction

Q2: Magnesium ribbon is rubbed before burning because it has a coating of

• basic magnesium carbonate
• basic magnesium oxide
• basic magnesium sulphide
• basic magnesium chloride

Q3: What chemicals are used in fireworks?

• Copper chloride
• Calcium chloride
• Barium chloride
• All of above

Q4: The chemical formula of lead sulphate is

• Pb2SO4
• Pb(SO4)2
• PbSO4
• Pb2(SO4)3

Q5: When a magnesium ribbon is burnt in the air, the ash formed is

• Black
• White
• Yellow
• Pink

Q6: Which information is not conveyed by a balanced chemical equation?

• Physical states of reactants and products
• Symbols and formulae of all the substances involved in a particular reaction
• Number of atoms/molecules of the reactants and products formed
• Whether a particular reaction is actually feasible or not

Q7: The color of magnesium oxide is

• White
• Blue
• Grey
• Pink

Q8: Chemically rust is

• hydrated ferrous oxide
• only ferric oxide
• hydrated ferric oxide
• none of these

Q9: When carbon dioxide is passed through lime water,

• Calcium hydroxide is formed
• A white precipitate of CaO is formed
• Lime water turns milky
• Color of lime water disappears.

Q10: Both CO2 and H2 gases are

• heavier than air
• colorless
• acidic in nature
• soluble in water

Q11: When crystals of lead nitrate are heated strongly in a dry test tube

• Crystals immediately melt
• A brown residue is left
• White fumes appear in the tube
• A yellow residue is left

Q12: Which of the following gases can be used for the storage of fresh samples of oil for a long time?

• Carbon dioxide or oxygen
• Nitrogen or helium
• Helium or oxygen
• Nitrogen or oxygen

Q13: Consider equations: Ca⁺²(aq) + 2OH‾(aq)→Ca(OH)₂ (s). The precipitate of calcium hydroxide will be of

• Green color
• Blue color
• Brown color
• White color

Q14: In writing chemical equations, the inclusion of state symbols shall be done while

• Correct chemical formulae of reactants and products are written
• The equation is being balanced to fulfill the law of conservation of mass
• The equation has been balanced
• The chemical formulae of products and reactants have been changed to bring about quick balancing

Q15: The electrolytic decomposition of water gives H2 and O2 in the ratio of

• 1: 2 by volume
• 2: 1 by volume
• 8: 1 by mass
• 1: 2 by mass

Q16: Consider the equation: Pb⁺² (aq) + 2OH⁻ (aq) → Pb(OH)₂ (s), the precipitate of lead (II) hydroxide will be of

• Green color
• Blue color
• Brown color
• White color

Q17: Consider the equation: Cu⁺² (aq) + 2OH⁻(aq) → Cu(OH)₂ (s), the precipitate of Copper Hydroxide (Cu(OH)₂) will be of

• Green color
• Blue color
• Brown color
• White color

Q18: In the decomposition of lead (II) nitrate to give lead (II) oxide, nitrogen dioxide, and oxygen gas, the coefficient of nitrogen dioxide (in the balanced equation) is

• 1
• 2
• 3
• 4

Q19: Consider reaction: Na(s) + O₂(g) → Na₂O(s). Moles of sodium needed to balance equation would be

• 1
• 2
• 3
• 4

Q20: Consider the reaction: S(s) + O₂(g) → SO₂. The state of SO₂ in this reaction is

• Liquid
• Solid
• Gaseous
• All Three

Q21: Fatty foods become rancid due to the process of

• oxidation
• corrosion
• reduction
• hydrogenation

Q22: Consider reaction: P(s) + O₂(g) → P₄O₁₀(s). Moles of O₂(g) needed to balance the equation will be

• 1
• 3
• 5
• 7

Q23: We store silver chloride in a dark-colored bottle because it is

• a white solid
• undergoes redox reaction
• to avoid action by sunlight
• None of the above

Q24: Consider reaction: Al(s) + O₂ (g) → Al₂O₃. Moles of Al(s) needed to balance equation are

• 1
• 2
• 3
• 4

Q25: Which one of the given processes involves chemical reactions?

• Storing of oxygen gas under pressure in a gas cylinder
• Keeping petrol in a China dish in the open
• Liquefaction of air
• Heating copper wire in the presence of air at high temperature

Q26: In which of the given 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 (g)
• 2H₂ (g) + O₂ (g) → 2H₂O (l)
• 2H₂ (g) + O₂ (g) → 2H₂O (g)

Q27: The silver article turns black when kept in the open for a few days due to the formation of

• H2S
• AgS
• AgSO4
• Ag2S

Q28: The reaction in which two compounds exchange their ions to form two new compounds is called

• Displacement reaction
• Combination reaction
• Double displacement reaction
• Redox reaction

Q29: Which of the given gases can be used for the storage of fresh samples of oil for a long time?

• Carbon dioxide or oxygen
• Nitrogen or helium
• Helium or oxygen
• Nitrogen or oxygen

Q30: An element X on exposure to moist air turns reddish-brown and a new compound Y is formed. The substance X and Y are

• X = Fe, Y = Fe2O3
• X = Ag, Y = Ag2S
• X = Cu, Y = CuO
• X = Al, Y = Al2O3

Q31: Which of the following are exothermic processes?

• Reaction of water with quick lime
• Dilution of an acid
• Evaporation of water
• Sublimation of camphor (crystals)

Q32: On immersing an iron nail in CuSO4 solution for few minutes, you will observe

• no reaction takes place
• the color of the solution fades away
• the surface of iron nails acquire a black coating
• the color of the solution changes to green

Q33: Rancidity can be prevented by

• adding antioxidants
• storing food away from light
• keeping food in the refrigerator
• all of these

Q34: In which of the following, heat energy will be evolved?

• Electrolysis of water
• Dissolution of NH4Cl in water
• Burning of L.P.G.
• Decomposition of AgBr in the presence of sunlight

Q35: Which of the following statements about the given reaction are correct? 3Fe(s) + 4H₂O(g) → Fe₃O₄ (s) + 4H₂ (g)

• Iron metal is getting oxidized.
• Water is getting reduced.
• Water is acting as reducing agent.
• Water is acting as oxidizing agent.

Q36: A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple color of the solution fades and finally disappears. Which of the given equation is the correct explanation for the observation?

• KMnO₄ is an oxidizing agent, it oxidizes FeSO₄
• FeSO₄ acts as an oxidizing agent and oxidizes KMnO₄
• The color disappears due to dilution, no reaction is involved
• KMnO₄ is an unstable compound and decomposes in the presence of FeSO₄ to a colorless compound

Q37: A teacher gave two test tubes to the students, one containing water and the other containing sodium hydroxide. She asked them to identify the test tube containing sodium hydroxide solution. Which one of the following can be used for identification?

• Blue litmus
• Red litmus
• Sodium carbonate solution
• Dilute hydrochloric acid

Q38: Magnesium ribbon is rubbed before burning because it has a coating of

• basic magnesium carbonate
• basic magnesium oxide
• basic magnesium sulphide
• basic magnesium chloride

Q39: Which of the following is not a physical change?

• Boiling of water to give water vapor
• Melting of ice to give water
• Dissolution of salt in water
• Combustion of Liquefied Petroleum Gas (LPG)

Q40: Which of the following statements about the given reaction are correct? 3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4 H2 (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

• Iron metal is getting oxidised
• Water is getting reduced
• Water is acting as reducing agent
• Water is acting as oxidising agent
• (i), (zi) and (iii)
• (in) and (iv)
• (i), (ii) and (iv)
• (ii) and (iv)

Q41: 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)

Q42: 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

Q43: A dilute ferrous sulphate solution was gradu¬ally added to the beaker containing acidified permanganate solution. The light purple color of the solution fades and finally disap¬pears. Which of the following is the correct explanation for the observation?

• KMnO4 is an oxidizing agent, it oxidizes FeSO4.
• FeSO4 acts as an oxidizing agent and oxidizes KMNO4.
• The color disappears due to dilution; no reaction is involved.
• KMnO4 is an unstable compound and decomposes in presence of FeSO4. to a colorless compound.

Q44: Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of reaction involved? (i) Displacement reaction (ii) Precipitation reaction (iii) Combination reaction (iv) Double displacement reaction

• Displacement reaction
• Precipitation reaction
• Combination reaction
• Double displacement reaction
• (i) only
• (ii) only
• (iv) only
• (ii) and (iv)

Q45: Pb + CuCl2 → PbCl2 + Cu. The above reaction is an example of:

• combination
• double displacement
• decomposition
• displacement

Q46: Combustion reactions are always

• Exothermic
• Endothermic
• Sometimes exothermic
• Both (a) and (b).

Q47: Which of the following is Not True with respect to the neutralization reaction?

• Salt is formed.
• Reaction occurs between an acid and a base.
• Reactive element displaces less reactive element.
• Reactants are in a gaseous state.

Q48: Name the products formed when iron filings are heated with dilute hydrochloric acid

• Fe (III) chloride and water
• Fe (II) chloride and water
• Fe (II) chloride and hydrogen gas
• Fe (III) chloride and hydrogen gas

Q49: The following reaction is used for the preparation of oxygen gas in the laboratory: 2KClO₃ (s) → 2KCl (s) + 3O₂ (g) Which of the following statement about the reaction is correct?

• It is a decomposition reaction and endothermic in nature.
• It is a combination reaction.
• It is a decomposition reaction and accompanied by the release of heat.
• It is a photochemical decomposition reaction and exothermic in nature.

Q50: The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:

• antioxidation
• reduction
• rancidity
• corrosion

Q51: A substance added to food containing fats and oils is called:

• Oxidant
• Rancid
• Coolant
• Antioxidant

Q52: Select the oxidising agent for the following reaction: H2S + I2 > 2HI + S

• I2
• H2S
• HI
• S

Q53: What type of chemical reactions takes place when electricity is passed through water?

• Displacement
• Combination
• Decomposition
• Double displacement

Q54: 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

Q55: When Ag is exposed to air it gets a black coating of

• AgNO3
• Ag2S
• Ag2O
• Ag2CO3

Q56: A substance ‘X’ is used in white-washing and is obtained by heating limestone in the absence of air. Identify ‘X’.

• CaOCl2
• Ca (OH)2
• CaO
• CaCO3

Q57: The process of reduction involves

• addition of oxygen
• addition of hydrogen
• removal of oxygen
• removal of hydrogen

Q58: 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)

• Reaction of water with quick lime
• Dilution of an acid
• Evaporation of water
• Sublimation of camphor (crystals)
• (i) and (ii)
• (ii) and (iii)
• (i) and (iv)
• (ii) and (iv)

Q59: Before burning in air, the magnesium ribbon is cleaned by rubbing with sandpaper to:

• Make the ribbon surface shinier
• Remove the layer of magnesium oxide from the ribbon surface
• Remove the layer of magnesium carbonate from the ribbon surface
• Remove the moisture from the ribbon surface

Q60: In a chemical reaction between sulphuric acid and barium chloride solution the white precipitates formed are of:

• Hydrochloric acid
• Barium sulphate
• Chlorine
• Sulphur

Q61: The respiration process during which glucose undergoes slow combustion by combining with oxygen in the cells of our body to produce energy is a kind of:

• Exothermic process
• Endothermic process
• Reversible process
• Physical process

Q62: A chemical reaction does not involve:

• Formation of new substances having entirely different properties than that of the reactants
• Breaking of old chemical bonds and formation of new chemical bonds
• Rearrangement of the atoms of reactants to form new products
• Changing of the atoms of one element into those of another element to form new products

Q63: One of the following processes does not involve a chemical reaction. That is:

• Melting of candle wax when heated
• Burning of candle wax when heated
• Digestion of food in our stomach
• Ripening of banana

Q64: It is necessary to balance a chemical equation in order to satisfy the law of:

• Conservation of motion
• Conservation of momentum
• Conservation of energy
• Conservation of mass

Q65: All the methods mentioned below can be used to prevent the food from getting rancid except: i. Storing the food in the air-tight containers ii. Storing the food in the refrigerator iii. Keeping the food in clean and covered containers iv. Always touching the food with clean hands

• (i) and (ii)
• (i) and (iii)
• (i), (iii) and (iv)
• (iii) and (iv)

Q66: Rusting of iron involves a chemical reaction which is a combination of:

• Reduction as well as combination reactions
• Oxidation as well as combination reactions
• Reduction as well as displacement reactions
• Oxidation as well as displacement reactions

Q67: When ferrous sulphate is heated strongly it undergoes decomposition to form ferric oxide as a main product accompanied by a change in color from:

• Blue to green.
• Green to blue.
• Green to brown.
• Green to yellow.

Q68: Which of the following gases is used in the storage of fat and oil-containing foods for a long time?

• Carbon dioxide gas
• Nitrogen gas
• Oxygen gas
• Neon gas

Q69: The displacement reaction between iron (III) oxide and a metal X is used for welding the rail tracks. Here X is:

• Copper granules
• Magnesium ribbon
• Sodium pellets
• Aluminium dust

Q70: The neutralization reaction between an acid and a base is a type of:

• Double displacement reaction
• Displacement reaction
• Addition reaction
• Decomposition reaction