Chemical Reaction MCQ Quiz - Objective Question with Answer for Chemical Reaction - Download Free PDF

The correct answer is poisons.

• Catalytic poisons are those substances that themselves are not catalysts but whose presence decreases the activity of the catalyst.
• This occurs due to preferential adsorption of poison on the surface of the catalyst.
• They are also known as anti catalysts or catalyst inhibitors.

​Catalyst:

• It is a substance that increases the rate of a reaction without taking a direct part in the reaction.
• Catalysts do not undergo chemical change in themselves.
• When we need to control the rate of reaction which has increased due to the addition of a catalyst, catalytic poisons are added.

Additional Information

Promoter

• It is a substance added to a solid catalyst to improve its performance in a chemical reaction.
• The promoter itself has little or no catalytic effect. 

Initiators

• Initiators are substances that help to initiate (start) a chemical reaction.

Controllers

• Controllers are used for controlling the rate of a chemical reaction.
• They can be mechanical, thermal, or chemical in nature.

The correct answer is Na₂O.

Key Points

• Neutral oxides are said to be oxides that do not show any properties of acids and bases.
• Neutral oxide is an oxide that does not react in the presence of any acid or base.
• Let us see other examples of the neutral oxides such as
  • CO
  • N₂O
  • NO
  • MnO₂
  • H₂O

Important Points

• Sodium Oxide having a chemical formula of Na₂O, is a metal oxide.
• It is also known as an alkali metal oxide as it comprises two sodium and one Oxygen atoms.

Additional Information

• Acidic Oxide:
  • It is said to be the oxides when reacted with the water molecule will give acids.
• Basic Oxide:
  • It is said to be the oxides when reacted with water molecules will give bases.
• Amphoteric Oxide:
  • It is said to be the oxides that can react as acid as well as bases.

CONCEPT:

Oxidation of Fats and Oils

• When fats and oils are exposed to air, they undergo a chemical reaction known as oxidation.
• Oxidation occurs due to the reaction of fats and oils with oxygen in the air, leading to the formation of compounds like aldehydes, ketones, and peroxides.
• This oxidation process is responsible for the phenomenon of rancidity, which results in a bad smell and taste in the food.

EXPLANATION:

• When fat and oil containing food materials are left outside for a long time:
  • The fats and oils react with oxygen present in the air.
  • This reaction causes the fats and oils to oxidize, forming new compounds that degrade the quality of the food.
• Oxidation is the primary reason for rancidity, which makes the food unfit for consumption over time.

Hence, the correct answer is Option 1: Fats and oils in the food get oxidized.

Therefore, when fats and oils in food are left outside for a long time, they get oxidized, leading to rancidity.

CONCEPT:

Oxidation and Reduction Reactions

• Oxidation involves the loss of electrons, gain of oxygen, or loss of hydrogen.
• Reduction involves the gain of electrons, loss of oxygen, or gain of hydrogen.
• The mnemonic "LEO the lion says GER" can be used to remember:
  • LEO: Loss of Electrons = Oxidation
  • GER: Gain of Electrons = Reduction

EXPLANATION:

•  If a substance loses hydrogen during a reaction, it is reduced.
  This is incorrect, as the loss of hydrogen signifies oxidation, not reduction.
• If a substance loses oxygen during a reaction, it is reduced.
  This is correct, as reduction involves the loss of oxygen.
• If a substance gains hydrogen during a reaction, it is reduced.
  This is correct, as reduction involves the gain of hydrogen.
• If a substance gains oxygen during a reaction, it is oxidized.
  This is correct, as oxidation involves the gain of oxygen.

The incorrect statement is If a substance loses hydrogen during a reaction, it is reduced.

Key Points

• Aluminium oxide (Al₂O₃) is an amphoteric oxide, meaning it reacts with both acids and bases.
• When Aluminium oxide reacts with hydrochloric acid (HCl), it forms Aluminium chloride (AlCl₃) and water.
• When Aluminium oxide reacts with sodium hydroxide (NaOH), it forms sodium aluminate (NaAlO₂) and water.
• This dual property of Aluminium oxide makes Aluminium (Al) the correct answer.

Important Points

• An amphoteric oxide is an oxide that reacts with both acids and bases to form salt and water.
• Aluminium oxide is a good example of an amphoteric oxide, as it reacts with acids like HCl and bases like NaOH.

Additional Information

• Na (Sodium): Sodium forms sodium oxide (Na₂O), which is a basic oxide. It does not react with bases like NaOH but reacts with acids to form salts.
• Mg (Magnesium): Magnesium forms magnesium oxide (MgO), which is a basic oxide. It reacts with acids.
• K (Potassium): Potassium forms potassium oxide (K₂O), which is a highly basic oxide. It reacts only with acids.

Explanation:

• Calcium hydroxide is sparingly soluble in water producing an alkaline solution known as limewater.
• Calcium Carbonate is a chemical compound found commonly in rocks as minerals and is the main component of pearls and the shells of marine organisms, eggs, etc.
• When carbon dioxide gas is passed through or over limewater, it turns milky due to the formation of calcium carbonate.
• In the chemical reaction it can be shown as :

\(\rm \underset{Lime\ water}{Ca (OH)_2} \ (aq) \ + \ \underset{Carbon \ Dioxide}{CO_2 \ (g) }\ \longrightarrow \ \underset{Calcium \ Carbonate}{CaCO_3 \ (g)}\)Ca(OH)2Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate" id="MathJax-Element-1-Frame" role="presentation" style="display: inline; position: relative;" tabindex="0">Ca(OH)2Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate" role="presentation" style="display: inline; position: relative;" tabindex="0">Ca(OH)2

• However, when an excess of CO2 ​is passed through this solution, the milkiness disappears. This is due to the formation of calcium bicarbonate which is colorless and soluble in water.

Ca(OH)2Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate" role="presentation" style="display: inline; position: relative;" tabindex="0">​\(\rm \underset{Lime\ water}{Ca (OH)_2} \ (aq) \ + \ \underset{Carbon \ Dioxide}{CO_2 \ (g) }\ \longrightarrow \ \underset{Calcium \ Carbonate}{CaCO_3 \ (g)}\)​\(\rm \underset{Lime\ water}{Ca CO_3} \ (aq) \ + \ \underset{Carbon \ Dioxide}{CO_2 \ (g) }\ \longrightarrow \ \underset{Calcium \ Carbonate}{Ca(HCO_3)_2 \ (g)}\)Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate\(\rm \underset{Calcium\ Carbonate}{Ca CO_3} \ \ +H_2O+ \ \underset{Carbon \ Dioxide}{CO_2 \ (g) } \ \longrightarrow \ \underset{Calcium \ bi\ Carbonate}{Ca(HCO_3)_2 \ (g)}\)

Additional Information Reaction involved-

CaCO₃ + 2HCl →  CaCl₂ + CO₂ + H₂O

• The evolved gas is carbon dioxide which then passes through lime water and turns it milky.

Ca(OH)₂ + CO₂ → H₂O + CaCO₃  

• Due to formation of these compounds
• when excess CO₂ is passed

CaCO₃ + H₂O + CO₂ →  Ca(HCO₃)₂ 

• Bicarbonate is formed which again clears the solution

Mistake Points

•  Do not confuse Calcium carbonate and calcium bicarbonate.
• One produces white colour while the other makes it colourless.

The correct answer is green.

Key Points 

• Barium Nitrate Ba(NO₃)₂ is an Oxidizer used to produce green colour in fireworks and fountains.
• This compound is also used in the production process of Barium Oxide in the vacuum tube industry.
• Barium is also used in medicine and oil and gas production.
• It is an inorganic compound that occurs with other elements like sulfur, oxygen, etc.
• Barium is found at 0.0425% on the earth’s crust, and 13 μg/L in seawater.
• It is a non-combustible compound but enhances the burning of combustible elements.
• The melting point of barium nitrate is 592 degrees Celcius.​

Additional Information

The correct answer is Double displacement reaction.

Concept:

Chemical reaction:

• It is a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
• A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

Explanation:

• Double displacement reaction: 

• It is a chemical reaction in which two compounds react and exchange their ions forming new products. 
• This reaction often results in the formation of an insoluble compound called a precipitate. 
• Such reactions are represented by equations of the following form: A⁺B^- + C⁺D^- → A⁺D^- + B^-C⁺

​In the given chemical reaction: 

NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)

The reactants NaCl and AgNO₃ have exchanged their ions to form NaNO3  and AgCl. 

Thus, it is an example of a double displacement reaction.^​

^{Additional Information}

Types of Chemical Reactions:

Combination reaction:

• Two or more elements or compounds combine together to form a single compound.
• Such reactions are represented by equations of the following form:     A + B → AB.

Decomposition reaction:

• The opposite of a combination reaction, a complex molecule breaks down to make simpler ones.
• Such reactions are represented by equations of the following form: AB → A + B.

Displacement reaction:

• One element takes place with another element in the compound.
• Such reactions are represented by equations of the following form: A + BC → AC + B.

Redox reaction:

• It is a reaction in which one species is reduced and the other is oxidized. 
• Reduction means losing Oxygen or gaining hydrogen 
• Oxidation means gaining oxygen or losing hydrogen. 

The correct answer is CaSO4.1/2 H2O.

​EXPLANATION:

• Plaster of Paris (POP) is a quick-setting gypsum plaster consisting of a fine white powder (calcium sulfate hemihydrate), which hardens when moistened and allowed to dry.
• It is also known as the Plaster of Paris because for the preparation of POP, the abundant gypsum was first found near the capital city of France i.e. Paris.
• The chemical formula of the Plaster of Paris is CaSO4.\(\frac{1}{2}\) H2O. Therefore option 3 is correct.
• Application of Plaster of Paris is as follows
  1. It is used as a building material as a protective coating on walls and ceilings.
  2. It is used as a moulding and vesting agent for decorative elements.
  3. It is also used for aesthetic touch to the construction elements.
  4. It is also used as plaster in orthopaedics and as a filling material by dentists, etc.

Mistake Points

\(\begin{array}{*{20}{c}} {CaS{O_{4.}} + \frac{1}{2}{H_2}O + 1\frac{1}{2}{H_2}O}\\ {\left( {Plaster\,Of\,Paris} \right)} \end{array} \to \begin{array}{*{20}{c}} {CaS{O_4}.2{H_2}O}\\ {\left( {Gypsum} \right)} \end{array}\)

• Gypsum is an ore of Calcium (Ca). The chemical formula of Gypsum is CaSO4. 2H2O.
• Gypsum is mainly used as a fertilizer, as the main constituent in plaster, chalk, etc.
• The plaster of Paris on mixing with water produces gypsum.
• Calcium Sulphate Hemihydrate (CaSO4·1/2 H2O) on hydration leads to the crystallization of gypsum calcium sulphate dihydrate (CaSO4·2H2O).

The correct answer is carbon dioxide.

Key Points

• Urea is now prepared commercially from liquid ammonia and liquid carbon dioxide.
• The chemical name of urea is carbamide, the diamide of carbonic acid.
• Its formula is NH₂CONH₂.
• Urea has important uses as a fertilizer and feeds supplement.
• It is a colourless substance existing in the crystalline form, which melts at 132.7°C (271° F).
• Urea is a waste product in the body with no physiological function.
• It dissolves in the kidney and blood before it is excreted as urine.

Important Points

• Uses of Urea
  • It is mainly used as a nitrogen release fertilizer.
  • Urea is used as a stabilizer in most nitrocellulose explosive products.
  • It is used in manufacturing high explosive materials like urea nitrate (CH₅N₃O₄).
  • It is used as an important reagent in lanthanide chemistry.
  • It is used in creams/ointments that are used for rehydration.
  • It is used in hair removal creams and dish soaps.
  • It is used as a browning agent for pretzels.
  • It is used in manufacturing melamine.
  • It is used to detect the bacteria in the stomach through the urea breath test.

The correct answer is oxidizing.

Key Points

• Potassium permanganate (KMnO₄) is a strong oxidizing agent that oxidizes dissolved impurities from water such as iron, manganese, and hydrogen sulfide (H₂S) by converting them into solid particles.
• These impurities are then filtered out of the water.
• It is a salt consisting of K⁺ and MnO^{− 4} ions.
• It is a strong oxidizing agent.
• It is used as a medication for cleaning wounds and dermatitis.

Additional Information

• Some other chemical disinfectants used for water:
  • Hypochloride
  • Chlorine dioxide
  • Chlorine
  • Hydrogen peroxide
  • Potassium permanganate
  • Gamma rays
  • Ultraviolet light

The correct answer is a Combination Reaction.

Key Points 

• The combustion of coal is an example of Combination Reaction.
• A combination reaction is a reaction where two or more elements or compounds combine to form a single compound. Such reactions are represented by equations of the following form: X + Y → XY.
• The combination of two or more elements to form one compound is called a combination reaction.

​

Additional Information 

Other types of Chemical Reactions:

• Decomposition reaction:
  • The opposite of a combination reaction, a complex molecule breaks down to make simpler ones. Such reactions are represented by equations of the following form: AB → A + B.
• Precipitation reaction: 
  • Two solutions of soluble salts are mixed resulting in an insoluble solid (precipitate) forming. Such reactions are represented by equations of the following form: A + Soluble salt B  → Precipitate + soluble salt C.
• Neutralization reaction: 
  • An acid and a base react with each other. Generally, the product of this reaction is salt and water. Such reactions are represented by equations of the following form: Acid + Base → Salt + Water.
• Combustion reaction: 
  • Oxygen combines with a compound to form carbon dioxide and water. These reactions are exothermic, meaning they give off heat. Such reactions are represented by equations of the following form: A + O2 → H2O + CO2.
• Displacement reaction: 
  • One element takes place with another element in the compound. Such reactions are represented by equations of the following form: A + BC → AC + B.
• Double displacement reaction:
  •  Double displacement reactions occur when a part of two ionic compounds is exchanged and makes two new components.
  •  Double displacement reactions take place mostly in aqueous solutions wherein the ions precipitate and the exchange of ions takes place.                

The correct answer is Mg(s) + Cl2(g) → Mgcl2(s).

Key Points

• Magnesium (Mg) combines with chlorine (Cl2) to form a new product as magnesium chloride (Mgcl2). Therefore its a combination reaction and the balanced equation can be written as:
  • Mg(s) + Cl2(g) → Mgcl2(s)​

Additional Information

• A combination reaction is a reaction where two or more elements or compounds combine to form a single compound. Such reactions are represented by equations of the following form: X + Y → XY.
• The combination of two or more elements to form one compound is called a combination reaction.
• Other types of Chemical Reactions:
  • Decomposition reaction: The opposite of a combination reaction, a complex molecule breaks down to make simpler ones. Such reactions are represented by equations of the following form: AB → A + B.
  • Precipitation reaction: Two solutions of soluble salts are mixed resulting in an insoluble solid (precipitate) forming. Such reactions are represented by equations of the following form: A + Soluble salt B  → Precipitate + soluble salt C.
  • Neutralization reaction: An acid and a base react with each other. Generally, the product of this reaction is a salt and water. Such reactions are represented by equations of the following form: Acid + Base → Salt + Water.
  • Combustion reaction: Oxygen combines with a compound to form carbon dioxide and water. These reactions are exothermic, meaning they give off heat. Such reactions are represented by equations of the following form: A + O2 → H2O + CO2.
  • Displacement reaction: One element takes place with another element in the compound. Such reactions are represented by equations of the following form: A + BC → AC + B.

The correct answer is an Oxidation reaction.

Key Points

• Rancidity refers to the spoilage of food in such a way that it becomes undesirable for consumption. 
• It is caused by the oxidation of fats and oils present in food.
• It causes changes in the taste and smell of food.

Additional Information

•  Rancidity can be controlled by
  • Adding antioxidants to foods.
  • Keeping food items in a closed container.
  • Refrigerating food.
  • Replacing oxygen in the containers with another gas.

The correct answer is Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH₃

Key Points

• The Displacement reaction is a reaction in which a more reactive element displaces a less reactive element from its compound present in a dissolved state.
• In the Double displacement reaction, there is an exchange of ions between the reactants to give new substances.
• In BaCl2 + H2SO4 → BaSO4 + 2HCl, positive (Ba⁺) and negative(Cl^-) ions of the two reactants switch places forming two new compounds and so it is a double displacement reaction.
  • In this, Barium Chloride (BaCl2) reacts with Sulphuric acid (H2SO4) to form Barium Sulphate (BaSO4) and Hydrochloric acid (HCl).
• In CuSO4 + H2S → CuS + H2SO4, Hydrogen Sulphide (H2S) reacts with Copper (II) Sulphate (CuSO4) and gives Copper Sulphide (CuS) and Sulphuric acid (H2SO4).
  • Here, Cu⁺ and SO₄^- exchange their ions and so, this is a double displacement reaction. 
• In Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH3, Magnesium nitride (Mg3N2) splits into two compounds namely Magnisium Hydroxide (3Mg(OH)2) and Ammonia (2NH3). 
  • A chemical reaction in which a single reactant or compound splits to form simpler products is called a Decomposition reaction.
  • So, this is not a Double displacement reaction, but a Decomposition reaction. Hence option 2 is correct.

Additional Information

• In NaOH + HCl → NaCl + H2O, Sodium (Na+) and OH- exchange ions and so this is a double displacement reaction.
  • This is also a Neutralization reaction because the acid and base reactants neutralize to become salt and water.
  • Sodium Hydroxide (NaOH) is a base and Hydrochloric acid (HCl) is an acid that combines to form a salt (NaCl) and release water (H2O).
• Magnesium nitride is a greenish-yellow colour that is commonly referred to as Trimagnisium dinitride.
  • ​It exists as a powder form at room temperature and normal pressure.
  • It can dissolve in acid and water as well but is slightly soluble in ethanol.
• Hydrogen Sulphide is a colourless chalcogen hydride poisonous and flammable gas with the foul smell of rotten eggs.
• Sulphuric acid also called the Oil of Vitriol has a strong acidic nature and is corrosive.
  • ​At high concentrations, it acts as an oxidizing agent and dehydrating agent.