Can you please provide me with all important questions of chemical reactions and equations
Can you please provide me with all important questions of chemical reactions and equations
1. What is a redox reaction?
Ans. A redox reaction is a reaction involving both oxidation and reduction occurs simultaneously.
2. What is corrosion? Explain its advantage and disadvantage.
Ans. Corrosion is defined as a natural process that causes the transformation of pure metals into undesirable substances when they react with substances like water or air. This reaction causes damage and disintegration of the metal starting from the portion of the metal exposed to the environment and spreading to the entire bulk of the metal.
Advantage:
A layer of protection: A layer of oxide is formed in surface corrosion, which protects the inner metal from corrosion. Sacrificial anodes such as zinc are used as a preventive measure to stop corrosion of other metals.
Disadvantage:
Corrosion can have a varying degree of effect on a lot of things. As such, it mainly causes waste of natural resources. Additionally, it can further cause hazardous situations such as building structures becoming weak and unstable, accidents caused by corroded parts as well as other unwanted failures such as cracked pipelines, bridges collapsing, transport vehicle crashes, or other catastrophes.
3. What is rancidity? How can we reduce the problem of rancidity?
Ans. Rancidity is a term that refers in the most general way to the spoilage of food in such a way that it becomes unacceptable for consumption. Food is rancid due to the presence of fats and oils within them are oxidized and the food’s smell and taste change
We can reduce the problem of Rancidity though
(1) by adding antioxidants
(2) Storing food away from light
(3) Keeping food in the refrigerator
4. How is corrosion different from rusting?
Ans.1. Corrosion is the gradual degradation of metals due to exposure to air and moisture.
2. When iron metal is exposed to an open environment, it undergoes a chemical reaction with oxygen and water in the air and forms a hydrated iron oxide which is known as the rust-brown reddish layer.
3. Corrosion of iron is also known as rusting since rust is the product that is being formed.
5. What is meant by endothermic and exothermic reactions? Give a suitable example for each.
Ans. Endothermic
1. The endothermic process is a term that describes a reaction where the system absorbs the energy from its surrounding in the form of heat.
2. A few examples of the endothermic process are photosynthesis, evaporating liquids, melting ice, dry ice, alkanes cracking, thermal decomposition, ammonium chloride in water, and much more.
Exothermic
1. The exothermic reaction is the opposite of an endothermic reaction. It releases energy by light or heat to its surrounding.
2. A few examples are neutralization, burning of a substance, reactions of fuels, deposition of dry ice, respiration, solution of sulphuric acid into water, and much more.
6. Define different types of a chemical reactions and give examples for each.
Combination Reaction
1. A reaction in which two or more reactants combine to form a single product is known as a combination reaction.
2. It takes the form of X + Y → XY
3. A combination reaction is also known as a synthesis reaction.
4. Example of combination reaction:2Na(s)+Cl2(g)⟶2NaCl(s)
Decomposition Reaction
1. A reaction in which a single compound breaks into two or more simpler compounds is known as a decomposition reaction.
2. It takes the form of XY → X + Y
3. A decomposition reaction is just the opposite of a combination reaction.
4. Example of decomposition reaction:CaCO3(s)⟶CaO(s)+CO2(g)
Displacement Reaction
1. A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
2. It takes the form X + YZ → XZ + Y
3. It is also called a substitution reaction
4. Example of displacement reaction: Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
Double Displacement Reaction
1. A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
2. It takes the form of XY + ZA → XZ + YA
3. It is also called a metathesis reaction
4. Example of double displacement reaction: BaCl2(aq)+Na2SO4(aq)⟶BaSO4(s)+2NaCl(aq)
Precipitation Reaction
1. A chemical reaction that involves the formation of an insoluble product (precipitate; solid) is called a Precipitation reaction.
2. The reactants are soluble, but the product formed would be insoluble and separates out as a solid.
3. A precipitation reaction occurs when a solution, originally containing dissolved species, produces a solid, which generally is denser and falls to the bottom of the reaction vessel.
4. Example of precipitation reaction: NaCl(aq)+AgNO3(aq)⟶AgCl(s)↓+NaNO3(aq)
7. Why is Photosynthesis considered an endothermic reaction?
Ans. Photosynthesis is considered an endothermic reaction because, during the process of photosynthesis, energy from the sun or sunlight is absorbed. Any chemical reaction that absorbs heat energy from the surroundings to form products is termed the endothermic reaction.
The chemical reaction of photosynthesis is: 6CO2(g)+H2O(g)+sunlight⟶C6H12O6(s)+6O2(g)
8. In the electrolysis of water, why is the volume of gas collected over one electrode double that of the other electrode?
Ans. The gas which is collected is double the amount during the electrolysis of water is hydrogen. This is because water contains two parts of hydrogen element as compared to one part of oxygen element by volume.
Electrolysis of water is given by the equation: 2H2+O2⟶2H2O
9. What happens when water is added to solid calcium oxide taken in a container? Write a chemical formula for the same.
Ans 1.When calcium oxide is added to water it forms calcium hydroxide Called slaked lime.
2. The chemical reaction can be depicted as: CaO(s)+2H2O(l)⟶Ca(OH)2(aq)
3. The reaction between water and CaO is an exothermic reaction.
4. Heat is released during an exothermic reaction , rise in temperature is observed.
10. Give one use of quick lime.
Ans. It is used as a basic flux. It is used in the refining of sugar and as a disinfectant and germicide
11. Give three types of decomposition reactions.
The three primary types of decomposition reactions are:
1. Thermal decomposition reaction
A thermal decomposition reaction can be defined as a decomposition reaction that is activated by thermal energy. In simpler words, a thermal decomposition reaction needs the energy to be supplied to the reactants in the form of heat.
These reactions are generally endothermic since energy is required to break the chemical bonds and separate the constituent elements
An example of a thermal decomposition reaction is: CaCO3(s)⟶CaO(s)+CO2(g)
2. Electrolytic decomposition reaction
An electrolytic decomposition reaction is a type of decomposition reaction in which the activation energy for decomposition is provided in the form of electrical energy.
An example of an electrolytic decomposition reaction is the electrolysis of water, which can be represented by the given chemical equation:2H2O⟶2H2+O2
Photo decomposition
A photodecomposition reaction is a type of decomposition reaction in which the reactant is broken down to its constituents by absorbing energy from photons.
An example of a photodecomposition reaction is the decomposition into dioxygen and an oxygen radical, as represented by the chemical equation provided below. O3+hv⟶O2+O
12. Name the compound used for testing CO2CO_2CO2gas.
Ans. A freshly prepared Calcium hydroxide solution, also called lime water, is used to test CO2 gas. when CO2 is passed through calcium hydroxide, it turns milky because of the formation of calcium carbonate.
13. Explain the process of corrosion and rusting. (2 marks)
Corrosion is defined as a natural process that causes the transformation of pure metals into undesirable substances when they react with substances like water or air. This reaction causes damage and disintegration of the metal starting from the portion of the metal exposed to the environment and spreading to the entire bulk of the metal.
Rusting: When iron metal is exposed to an open environment, it undergoes a chemical reaction with oxygen and water in the air and forms a hydrated iron oxide which is known as the rust-brown reddish layer. Corrosion of iron is also known as rusting since rust is the product that is being formed.
14. How is an exothermic reaction different from an endothermic reaction? (3 marks)
Endothermic
1. The endothermic process is a term that describes a reaction where the system absorbs the energy from its surrounding in the form of heat.
2. A few examples of the endothermic process are photosynthesis, evaporating liquids, melting ice, dry ice, alkanes cracking, thermal decomposition, ammonium chloride in water, and much more.
Exothermic
1. The exothermic reaction is the opposite of an endothermic reaction. It releases energy by light or heat to its surrounding.
2. A few examples are neutralization, burning of a substance, reactions of fuels, deposition of dry ice, respiration, solution of sulphuric acid into water, and much more.
15. Explain four different types of chemical reactions with suitable examples. (8 marks)
Combination Reaction
1. A reaction in which two or more reactants combine to form a single product is known as a combination reaction.
2. It takes the form of X + Y → XY
3. A combination reaction is also known as a synthesis reaction.
4. Example of combination reaction: 2Na(s)+Cl2(g)⟶2NaCl(s)
Decomposition Reaction
1. A reaction in which a single compound breaks into two or more simpler compounds is known as a decomposition reaction.
2. It takes the form of XY → X + Y
3. A decomposition reaction is just the opposite of a combination reaction.
4. Example of a decomposition reaction: CaCO3(s)⟶CaO(s)+CO2(g)
Displacement Reaction
1. A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
2. It takes the form X + YZ → XZ + Y
3. It is also called a substitution reaction
4. Example of displacement reaction: Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
Double Displacement Reaction
1. A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
2. It takes the form of XY + ZA → XZ + YA
3. It is also called a metathesis reaction
4. Example of double displacement reaction: BaCl2(aq)+Na2SO4(aq)⟶BaSO4(s)+2NaCl(aq)
16. How do we balance a chemical equation? (4 marks)
Ans.Step 1
The unbalanced equation must be obtained from the chemical formulae of the reactants and the products (if it is not already provided).
Step 2
The total number of atoms of each element on the reactant side and the product side must be compared. For this example, the number of atoms on each side can be tabulated
Step 3
1. Now, stoichiometric coefficients are added to molecules containing an element that has a different number of atoms on the reactant side and the product side.
2. The coefficient must balance the number of atoms on each side.
3. Generally, the stoichiometric coefficients are assigned to hydrogen and oxygen atoms last.
4. Now, the number of atoms of the elements on the reactant and product side must be updated.
5. It is important to note that the number of atoms of an element in one species must be obtained by multiplying the stoichiometric coefficient by the total number of atoms of that element present in 1 molecule of the species.
17. Why are oil and fat-containing food items flushed with nitrogen? (3 marks)
Ans. The main objective of flushing Nitrogen into food packets containing oil and fat products is to avoid rancidity, which results when the oil or fat combines with oxygen and produces an unpleasant odour and taste. As a result, flushing Nitrogen creates an unreactive environment, which prevents rancidity.
18. What is the difference between displacement and double displacement reactions? Give suitable chemical equations for the same. (3 marks)
Ans. Displacement Reaction
1. A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
2. It takes the form X + YZ → XZ + Y
3. It is also called a substitution reaction
4. Example of displacement reaction: Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
Double Displacement Reaction
1. A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
2. It takes the form of XY + ZA → XZ + YA
3. It is also called a metathesis reaction
4. Example of double displacement reaction:BaCl2(aq)+Na2SO4(aq)⟶BaSO4(s)+2NaCl(aq)
19. Give two uses of quick lime. (2 marks)
Ans. Uses of quick lime are: It is used in the manufacturing of cement, paper, and high-grade steel. It is the cheapest alkali available which is an important ingredient in the manufacturing of caustic soda.
20. What is electrolytic decomposition? (2 marks)
Ans. Electrolytic decomposition reaction
1. An electrolytic decomposition reaction is a type of decomposition reaction in which the activation energy for decomposition is provided in the form of electrical energy.
2. An example of an electrolytic decomposition reaction is the electrolysis of water, which can be represented by the given chemical equation 2H2O⟶2H2+O2
21. Identify the following type of reactions:-
▪ Na2SO4 + BaCl2 ⟶\longrightarrow⟶ BaSO4 + 2NaCl
▪ CaCO3 ⟶\longrightarrow⟶ CaO + CO2
▪ Fe + CuSO4 ⟶\longrightarrow⟶ FeSO4 + Cu (3 marks)
Ans. (1) Double displacement reaction
(2) Decomposition reaction
(3) Displacement reaction
22. What happens chemically when quicklime is added to water.
Ans. 1.When calcium oxide is added to water it forms calcium hydroxide Called slaked lime.
2. The chemical reaction can be depicted as: CaO(s)+2H2O(l)⟶Ca(OH)2(aq)
23 . Which gas is liberated when hydrochloric acid reacts with active metal.
Ans. Hydrogen gas is liberated when hydrochloric acid reacts with active metal.
24. What is an oxidation reaction. Is this endothermic or exothermic and state one example of oxidation reaction.
Ans. Oxidation Reaction: The addition of oxygen or removal of hydrogen to a substance is called oxidation.
Oxidation reactions are exothermic in nature, that is heat is evolved during the reaction.
For example: C(s)+O2(g)⟶CO2(g)+heat
25. Write the chemical equation for the reaction in which the following changes have taken place with an example of each
(i) Change in color
(ii) Change in temperature
(iii) Formation of a precipitate
(i) Change in color
An iron nail dipped in the solution of copper sulfate then iron displaces copper from the solution of copper sulfate because iron is more reactive than copper. Therefore copper sulfate solution color changes from blue to pale green.
The chemical reaction is given as: Fe(s)+CuSO4(aq)⟶FeSO4(aq)+Cu(s)
(ii) Change in temperature
When carbon is combusted, carbon dioxide is produced along with some amount of heat, hence the reaction is exothermic, rise in temperature is observed.
The chemical reaction is given as: C(s)+O2(g)⟶CO2(g)+heat
(iii) Formation of a precipitate
When sodium chloride reacts with silver nitrate solution, then silver chloride is precipitated.
The chemical reaction is given as:NaCl(aq)+AgNO3(aq)⟶AgCl(s)↓+NaNO3(aq)
26 - 2gram of ferrous sulfate crystals are heated in a dry boiling tube
(i) List any two observ
at
ions
(ii) Name the type of chemical reaction taking place
(iii) Write the chemical equation for the reaction
(i) Observations
1. Green color of ferrous sulfate disappears which means a change in state and colour occurs.
2. The reddish brown solid is formed and a gas is generated during this process.
(ii) It is a decomposition reaction since the compound (ferrous sulphate) decomposes into two or more substances.
(iii) The chemical reaction is given as: 2FeSO4(s)+heat⟶Fe2O3(s)+SO2(g)+SO3(g)
1. What is a redox reaction?
Ans. A redox reaction is a reaction involving both oxidation and reduction occurs simultaneously.
2. What is corrosion? Explain its advantage and disadvantage.
Ans. Corrosion is defined as a natural process that causes the transformation of pure metals into undesirable substances when they react with substances like water or air. This reaction causes damage and disintegration of the metal starting from the portion of the metal exposed to the environment and spreading to the entire bulk of the metal.
Advantage:
A layer of protection: A layer of oxide is formed in surface corrosion, which protects the inner metal from corrosion. Sacrificial anodes such as zinc are used as a preventive measure to stop corrosion of other metals.
Disadvantage:
Corrosion can have a varying degree of effect on a lot of things. As such, it mainly causes waste of natural resources. Additionally, it can further cause hazardous situations such as building structures becoming weak and unstable, accidents caused by corroded parts as well as other unwanted failures such as cracked pipelines, bridges collapsing, transport vehicle crashes, or other catastrophes.
3. What is rancidity? How can we reduce the problem of rancidity?
Ans. Rancidity is a term that refers in the most general way to the spoilage of food in such a way that it becomes unacceptable for consumption. Food is rancid due to the presence of fats and oils within them are oxidized and the food’s smell and taste change
We can reduce the problem of Rancidity though
(1) by adding antioxidants
(2) Storing food away from light
(3) Keeping food in the refrigerator
4. How is corrosion different from rusting?
Ans.1. Corrosion is the gradual degradation of metals due to exposure to air and moisture.
2. When iron metal is exposed to an open environment, it undergoes a chemical reaction with oxygen and water in the air and forms a hydrated iron oxide which is known as the rust-brown reddish layer.
3. Corrosion of iron is also known as rusting since rust is the product that is being formed.
5. What is meant by endothermic and exothermic reactions? Give a suitable example for each.
Ans. Endothermic
1. The endothermic process is a term that describes a reaction where the system absorbs the energy from its surrounding in the form of heat.
2. A few examples of the endothermic process are photosynthesis, evaporating liquids, melting ice, dry ice, alkanes cracking, thermal decomposition, ammonium chloride in water, and much more.
Exothermic
1. The exothermic reaction is the opposite of an endothermic reaction. It releases energy by light or heat to its surrounding.
2. A few examples are neutralization, burning of a substance, reactions of fuels, deposition of dry ice, respiration, solution of sulphuric acid into water, and much more.
6. Define different types of a chemical reactions and give examples for each.
Combination Reaction
1. A reaction in which two or more reactants combine to form a single product is known as a combination reaction.
2. It takes the form of X + Y → XY
3. A combination reaction is also known as a synthesis reaction.
4. Example of combination reaction:2Na(s)+Cl2(g)⟶2NaCl(s)
Decomposition Reaction
1. A reaction in which a single compound breaks into two or more simpler compounds is known as a decomposition reaction.
2. It takes the form of XY → X + Y
3. A decomposition reaction is just the opposite of a combination reaction.
4. Example of decomposition reaction:CaCO3(s)⟶CaO(s)+CO2(g)
Displacement Reaction
1. A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
2. It takes the form X + YZ → XZ + Y
3. It is also called a substitution reaction
4. Example of displacement reaction: Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
Double Displacement Reaction
1. A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
2. It takes the form of XY + ZA → XZ + YA
3. It is also called a metathesis reaction
4. Example of double displacement reaction: BaCl2(aq)+Na2SO4(aq)⟶BaSO4(s)+2NaCl(aq)
Precipitation Reaction
1. A chemical reaction that involves the formation of an insoluble product (precipitate; solid) is called a Precipitation reaction.
2. The reactants are soluble, but the product formed would be insoluble and separates out as a solid.
3. A precipitation reaction occurs when a solution, originally containing dissolved species, produces a solid, which generally is denser and falls to the bottom of the reaction vessel.
4. Example of precipitation reaction: NaCl(aq)+AgNO3(aq)⟶AgCl(s)↓+NaNO3(aq)
7. Why is Photosynthesis considered an endothermic reaction?
Ans. Photosynthesis is considered an endothermic reaction because, during the process of photosynthesis, energy from the sun or sunlight is absorbed. Any chemical reaction that absorbs heat energy from the surroundings to form products is termed the endothermic reaction.
The chemical reaction of photosynthesis is: 6CO2(g)+H2O(g)+sunlight⟶C6H12O6(s)+6O2(g)
8. In the electrolysis of water, why is the volume of gas collected over one electrode double that of the other electrode?
Ans. The gas which is collected is double the amount during the electrolysis of water is hydrogen. This is because water contains two parts of hydrogen element as compared to one part of oxygen element by volume.
Electrolysis of water is given by the equation: 2H2+O2⟶2H2O
9. What happens when water is added to solid calcium oxide taken in a container? Write a chemical formula for the same.
Ans 1.When calcium oxide is added to water it forms calcium hydroxide Called slaked lime.
2. The chemical reaction can be depicted as: CaO(s)+2H2O(l)⟶Ca(OH)2(aq)
3. The reaction between water and CaO is an exothermic reaction.
4. Heat is released during an exothermic reaction , rise in temperature is observed.
10. Give one use of quick lime.
Ans. It is used as a basic flux. It is used in the refining of sugar and as a disinfectant and germicide
11. Give three types of decomposition reactions.
The three primary types of decomposition reactions are:
1. Thermal decomposition reaction
A thermal decomposition reaction can be defined as a decomposition reaction that is activated by thermal energy. In simpler words, a thermal decomposition reaction needs the energy to be supplied to the reactants in the form of heat.
These reactions are generally endothermic since energy is required to break the chemical bonds and separate the constituent elements
An example of a thermal decomposition reaction is: CaCO3(s)⟶CaO(s)+CO2(g)
2. Electrolytic decomposition reaction
An electrolytic decomposition reaction is a type of decomposition reaction in which the activation energy for decomposition is provided in the form of electrical energy.
An example of an electrolytic decomposition reaction is the electrolysis of water, which can be represented by the given chemical equation:2H2O⟶2H2+O2
Photo decomposition
A photodecomposition reaction is a type of decomposition reaction in which the reactant is broken down to its constituents by absorbing energy from photons.
An example of a photodecomposition reaction is the decomposition into dioxygen and an oxygen radical, as represented by the chemical equation provided below. O3+hv⟶O2+O
12. Name the compound used for testing CO2CO_2CO2gas.
Ans. A freshly prepared Calcium hydroxide solution, also called lime water, is used to test CO2 gas. when CO2 is passed through calcium hydroxide, it turns milky because of the formation of calcium carbonate.
13. Explain the process of corrosion and rusting. (2 marks)
Corrosion is defined as a natural process that causes the transformation of pure metals into undesirable substances when they react with substances like water or air. This reaction causes damage and disintegration of the metal starting from the portion of the metal exposed to the environment and spreading to the entire bulk of the metal.
Rusting: When iron metal is exposed to an open environment, it undergoes a chemical reaction with oxygen and water in the air and forms a hydrated iron oxide which is known as the rust-brown reddish layer. Corrosion of iron is also known as rusting since rust is the product that is being formed.
14. How is an exothermic reaction different from an endothermic reaction? (3 marks)
Endothermic
1. The endothermic process is a term that describes a reaction where the system absorbs the energy from its surrounding in the form of heat.
2. A few examples of the endothermic process are photosynthesis, evaporating liquids, melting ice, dry ice, alkanes cracking, thermal decomposition, ammonium chloride in water, and much more.
Exothermic
1. The exothermic reaction is the opposite of an endothermic reaction. It releases energy by light or heat to its surrounding.
2. A few examples are neutralization, burning of a substance, reactions of fuels, deposition of dry ice, respiration, solution of sulphuric acid into water, and much more.
15. Explain four different types of chemical reactions with suitable examples. (8 marks)
Combination Reaction
1. A reaction in which two or more reactants combine to form a single product is known as a combination reaction.
2. It takes the form of X + Y → XY
3. A combination reaction is also known as a synthesis reaction.
4. Example of combination reaction: 2Na(s)+Cl2(g)⟶2NaCl(s)
Decomposition Reaction
1. A reaction in which a single compound breaks into two or more simpler compounds is known as a decomposition reaction.
2. It takes the form of XY → X + Y
3. A decomposition reaction is just the opposite of a combination reaction.
4. Example of a decomposition reaction: CaCO3(s)⟶CaO(s)+CO2(g)
Displacement Reaction
1. A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
2. It takes the form X + YZ → XZ + Y
3. It is also called a substitution reaction
4. Example of displacement reaction: Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
Double Displacement Reaction
1. A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
2. It takes the form of XY + ZA → XZ + YA
3. It is also called a metathesis reaction
4. Example of double displacement reaction: BaCl2(aq)+Na2SO4(aq)⟶BaSO4(s)+2NaCl(aq)
16. How do we balance a chemical equation? (4 marks)
Ans.Step 1
The unbalanced equation must be obtained from the chemical formulae of the reactants and the products (if it is not already provided).
Step 2
The total number of atoms of each element on the reactant side and the product side must be compared. For this example, the number of atoms on each side can be tabulated
Step 3
1. Now, stoichiometric coefficients are added to molecules containing an element that has a different number of atoms on the reactant side and the product side.
2. The coefficient must balance the number of atoms on each side.
3. Generally, the stoichiometric coefficients are assigned to hydrogen and oxygen atoms last.
4. Now, the number of atoms of the elements on the reactant and product side must be updated.
5. It is important to note that the number of atoms of an element in one species must be obtained by multiplying the stoichiometric coefficient by the total number of atoms of that element present in 1 molecule of the species.
17. Why are oil and fat-containing food items flushed with nitrogen? (3 marks)
Ans. The main objective of flushing Nitrogen into food packets containing oil and fat products is to avoid rancidity, which results when the oil or fat combines with oxygen and produces an unpleasant odour and taste. As a result, flushing Nitrogen creates an unreactive environment, which prevents rancidity.
18. What is the difference between displacement and double displacement reactions? Give suitable chemical equations for the same. (3 marks)
Ans. Displacement Reaction
1. A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
2. It takes the form X + YZ → XZ + Y
3. It is also called a substitution reaction
4. Example of displacement reaction: Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
Double Displacement Reaction
1. A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
2. It takes the form of XY + ZA → XZ + YA
3. It is also called a metathesis reaction
4. Example of double displacement reaction:BaCl2(aq)+Na2SO4(aq)⟶BaSO4(s)+2NaCl(aq)
19. Give two uses of quick lime. (2 marks)
Ans. Uses of quick lime are: It is used in the manufacturing of cement, paper, and high-grade steel. It is the cheapest alkali available which is an important ingredient in the manufacturing of caustic soda.
20. What is electrolytic decomposition? (2 marks)
Ans. Electrolytic decomposition reaction
1. An electrolytic decomposition reaction is a type of decomposition reaction in which the activation energy for decomposition is provided in the form of electrical energy.
2. An example of an electrolytic decomposition reaction is the electrolysis of water, which can be represented by the given chemical equation 2H2O⟶2H2+O2
21. Identify the following type of reactions:-
▪ Na2SO4 + BaCl2 ⟶\longrightarrow⟶ BaSO4 + 2NaCl
▪ CaCO3 ⟶\longrightarrow⟶ CaO + CO2
▪ Fe + CuSO4 ⟶\longrightarrow⟶ FeSO4 + Cu (3 marks)
Ans. (1) Double displacement reaction
(2) Decomposition reaction
(3) Displacement reaction
22. What happens chemically when quicklime is added to water.
Ans. 1.When calcium oxide is added to water it forms calcium hydroxide Called slaked lime.
2. The chemical reaction can be depicted as: CaO(s)+2H2O(l)⟶Ca(OH)2(aq)
23 . Which gas is liberated when hydrochloric acid reacts with active metal.
Ans. Hydrogen gas is liberated when hydrochloric acid reacts with active metal.
24. What is an oxidation reaction. Is this endothermic or exothermic and state one example of oxidation reaction.
Ans. Oxidation Reaction: The addition of oxygen or removal of hydrogen to a substance is called oxidation.
Oxidation reactions are exothermic in nature, that is heat is evolved during the reaction.
For example: C(s)+O2(g)⟶CO2(g)+heat
25. Write the chemical equation for the reaction in which the following changes have taken place with an example of each
(i) Change in color
(ii) Change in temperature
(iii) Formation of a precipitate
(i) Change in color
An iron nail dipped in the solution of copper sulfate then iron displaces copper from the solution of copper sulfate because iron is more reactive than copper. Therefore copper sulfate solution color changes from blue to pale green.
The chemical reaction is given as: Fe(s)+CuSO4(aq)⟶FeSO4(aq)+Cu(s)
(ii) Change in temperature
When carbon is combusted, carbon dioxide is produced along with some amount of heat, hence the reaction is exothermic, rise in temperature is observed.
The chemical reaction is given as: C(s)+O2(g)⟶CO2(g)+heat
(iii) Formation of a precipitate
When sodium chloride reacts with silver nitrate solution, then silver chloride is precipitated.
The chemical reaction is given as:NaCl(aq)+AgNO3(aq)⟶AgCl(s)↓+NaNO3(aq)
26 - 2gram of ferrous sulfate crystals are heated in a dry boiling tube
(i) List any two observ
at
ions
(iii) Write the chemical equation for the reaction
(i) Observations
1. Green color of ferrous sulfate disappears which means a change in state and colour occurs.
2. The reddish brown solid is formed and a gas is generated during this process.
(ii) It is a decomposition reaction since the compound (ferrous sulphate) decomposes into two or more substances.
(iii) The chemical reaction is given as: 2FeSO4(s)+heat⟶Fe2O3(s)+SO2(g)+SO3(g)
