Class 10: Chemical Reaction

UNIT 14: CHEMICAL REACTION

Multiple Choice Questions [1 mark each]

1.    When hydrogen reacts with oxygen, it forms water. What type of chemical reaction is it?

a) Combination reaction                       b) Decomposition reaction

c) Displacement reaction                      d) Neutralization reaction

2.    Which of the following is double displacement reaction?

a) Zn+HCl               Zncl₂                                 b) CaCO₃                     CaO + CO₂

          c) AgNO₃ + NaCl              NaNO₃ + AgCl        d) H₂ + O₂                 H₂O

3.    Complete the chemical reaction: H₂O₂            ……… + O₂

a) H₂                       b) H                        C) OH                     d) H₂O

4.    Which of the following is a negative catalyst?

a) Manganese dioxide        b) Molybdenum       c) Ferrous oxide d) glycerine  

5.    What does (↑) symbol represent in chemical equation?

a) solid                    b) liquid                  c) gas                      d) aqueous solution

6.    Which of the following condition is required by the green plants to prepare glucose?

a) Heat                   b) light                   c) pressure             d) electricity

7.    What is the chemical reaction in which the product is always an element and a compound?

a) Combination reaction                       b) Decomposition reaction

c) Single displacement reaction            d) Double displacement reaction

8.    In which chemical reaction, does the exchange of similar charged ions or groups between two reactants take place?

9.    a) Combination      b) decomposition    c) single displacement          d) double displacement

10.  

Answers: 1(a), 2(c), 3(d), 4(d), 5(c), 6(b),

Very Short Answer Questions [1mark each]

1. Define Chemical reaction.

The combination, decomposition or displacement that occurs in the molecules of matters during a chemical change is called a chemical reaction.

2. What is a combination reaction?
3. A chemical reaction in which two or more reactants combine to give a single product is called combination reaction or additional reaction.
4. What do you mean by decomposition reaction? Write with an example.

A chemical reaction in which a single reactant is broken down into two or more products is decomposition reaction. For example: KClO₃                      MnO₂              KCl + O₂

5. Define double displacement reaction with an example.

A chemical reaction in which an element or a radical of a compound is mutually displaced by an element or radical of another compound forming two different products is called double displacement reaction. For example:

AgNO₃ + NaCl                                               AgCl + NaNO₃

6. Name the factors that affect the rate of chemical reaction.

The factors that affect the rate of chemical reaction are: concentration of reactants, temperature, catalyst, nature of reactants, surface area of reactants and pressure.

7. What is acid-base reaction? Write with an example.

A chemical reaction in which an acid reacts with base to form salt and water is called acid-base reaction or neutralization reaction. An example of acid base reaction is as follows:

HCl (acid) + NaOH (base)                              NaCl + H₂O

 

8. Define exothermic chemical reaction with an example.

The chemical reaction in which heat energy is released is called exothermic chemical reaction. For example:

C + O₂                                     CO₂ + Q (heat)

9. Write a balanced chemical equation to show double displacement reaction.

A balanced chemical equation to show double displacement reaction is:

AgNO₃ + NaCl                                               AgCl + NaNO₃

10.           What is the rate of chemical reaction?

Rate of chemical reaction is the rate at which a chemical reaction is completed.

11. Define single displacement reaction with an example.

The chemical reaction in which an element or a radical of a compound is displaced by another radical or element is called single displacement reaction. For example:

Zn + H₂SO₄                             ZnSO₄ + H₂

In the above equation, Zn displaces H₂ from H₂SO_4.

12. Name the gases evolved at anode and cathode during electrolysis of water.

The gas evolved at anode is oxygen and at cathode is hydrogen during the electrolysis of water.

13. What substance causes a chemical reaction without itself being affected?

Catalyst causes a chemical reaction without itself being affected.

14. What is catalyst?

A catalyst is a chemical substance that accelerates or retards the rate of chemical reaction without undergoing any change in itself.

15. What is promoter? Give an example.

Promoter is a chemical substance which increases the activity of the catalyst. For example: In the preparation of NH₃ by Haber's process, Fe act as catalyst whose activity is increased by Mo.

16. What is called neutralization reaction?

The chemical reaction between an acid and base is called neutralization reaction.

17.   What is the essential characteristic of a chemical reaction?

A chemical reaction is a change process where there is loss and gain or sharing of electrons between reactants to form products.

18.  How is a chemical equation defined?

A chemical equation is the chemical formula in which the reactants and products of a reaction are written using words, symbols, or chemical formulas.

19.  What is a combination reaction?

It is a reaction in which two or more reactants combine to form only one product.

20.   Give a chemical example of a combination reaction .

2Na+Cl₂​→2NaCl (Sodium and Chlorine forming Sodium Chloride).

21.  What defines a decomposition reaction?

 A decomposition reaction is one in which a single reactant breaks down into two or more products.

22.  Write the reaction showing the decomposition of limestone () due to heat.

CaCO₃​(s)→CaO(s)+CO₂​(g)

23.  What is a displacement reaction?

It is a reaction in which an atom or radical of one reactant is displaced by the atom or radical of another reactant.

24.  In the reaction Zn+H₂​SO₄​→ZnSO₄​+H₂, what type of displacement occurs?

This is a single displacement reaction.

25.  What characterizes a double displacement reaction?

Two new compounds are formed by the mutual exchange of atoms or radicals between two reactants.

26.  What is the alternative name for an acid-base reaction?

An acid-base reaction is also known as a neutralization reaction.

27.  Define the rate of chemical reaction.

It is the change of reactants to products per unit time in any chemical reaction.

28.  In a reaction, what happens to the concentration of reactants and products over time?

The concentration of reactants goes on decreasing, and the concentration of products goes on increasing with time.

29.  How does increasing the temperature affect the rate of a chemical reaction?

Generally, the rate of chemical reaction increases with the increase in temperature.

30.  How does increasing the pressure affect the rate of chemical reactions involving gases?

The reaction takes place with greater speed when the pressure is increased.

31.  How does using a powdered form (increased surface area) of a reactant affect the reaction rate?

If the surface area of contact of reactants is more, the rate of reaction is also more (or faster).

32.  What is a catalyst?

33.  A catalyst is a substance that changes the rate of chemical reaction but does not undergo permanent chemical change during the reaction.

34.  Give an example of a positive catalyst mentioned in the text.

Manganese dioxide (MNO₂) or Iron (Fe) or Vanadium Pentoxide (V₂O₅).

35.  Give an example of a negative catalyst mentioned in the text.

Phosphoric acid (H₃PO₄).

36.  In the reaction , what substance is used as a positive catalyst?

Manganese dioxide (MnO₂) is used as a positive catalyst.

37.  What external factor determines the rate of photosynthesis?

The presence of light increases the rate of reaction

 

Short Answer Questions [2 Marks each]

1. Write a balanced equation of the chemical reaction between calcium chloride and silver nitrate. Also mention the type of chemical reaction.

The balanced chemical equation of the chemical reaction between calcium chloride and silver nitrate is

2AgNO₃ + CaCl₂                                2AgCl + 2NaNO₃

2. What happens when a solution of silver nitrate is added into the solution of sodium chloride? Write a balanced chemical equation of acid base reaction.

When a solution of silver nitrate is added into the solution of sodium chloride then Silver chloride is precipitate out.

A balanced chemical reaction between Acid and base is:HCl + NaOH                          NaCl + H₂O

3. Write the balanced chemical equation of the reaction between sodium hydroxide and hydrochloric acid. Also mention the type of chemical reaction.

The balanced chemical reaction between sodium hydroxide and hydrochloric acid is :

 NaOH + HCl                          NaCl + H₂O

The type of chemical reaction is acid-base or neutralization reaction.

4. Change the given word equation into balanced chemical equation. What type of chemical reaction is it? What is the role of MnO₂ in this reaction?

Potassium Chlorate     MnO₂    Potassium chloride + Oxygen

KClO₃             MnO₂              KCl + O₂

It is decomposition reaction. The role of MnO₂ is to increase the rate of chemical reaction.

5. In what condition do sodium chloride and Silver nitrate react? Write the balanced chemical equation of that reaction.

Sodium Chloride and Silver nitrate reacts in aqueous solution state.

AgNO₃ + NaCl                                               AgCl + NaNO₃

6. Write the relationship between the rate of chemical reaction and surface area of reaction.

Rate of chemical reaction increases with the increase in the surface area of reactants. This is because increase in surface area increases the chances of the particles to come in contact with each other.

7. Change the given word equation into balanced chemical equation. What type of reaction is it? Mention the type of chemical reaction with reason.
8. Hydrogen peroxide   ^Glycerol              Water + Oxygen

2H₂O₂                          ^Glycerol               2H₂O + O₂

The type of chemical reaction is decomposition reaction because in this reaction H₂O₂ get decomposed into two products i.e. H₂O and O₂.

9. Write the balanced chemical equation of the decomposition reaction which is carried out by catalyst. What is the function of the catalyst.

The balanced chemical equation of the decomposition reaction which is carried out with catalyst is :

2H₂O₂                          ^MnO₂                 2H₂O + O₂

The function of the catalyst is to increase the rate of chemical reaction.

10. Which type of chemical equation is given below? Define it.
11. Fe + CuSO₄                FeSO₄ + Cu↓

Single displacement chemical equation is given below.

The chemical reaction in which an element or a radical of a compound is displaced by another radical or element is called single displacement reaction.

12. How does the concentration of sodium thiosulphate affect the rate of reaction in between the hydrochloric acid and Sodium thiosulphate.

The rate of reaction between hydrochloric acid and sodium thiosulphate increases with the increase in the concentration of sodium thiosulphate. This is because the chance of molecular collision increases by decreasing their distance between molecules.

13. Why is the reaction between hydrochloric acid and sodium hydroxide called neutralization reaction?

The reaction between hydrochloric acid and sodium hydroxide is called neutralization reaction because both of them loses their properties and form neutral salt and water.

14. The rate of chemical reaction increases when the concentration of the reactants increases, why?

The rate of chemical reaction increases when the concentration of the reactants increases. This is because the increase in the concentration in the reactants brings the molecules of the reactants closer and hence the collision between the reactants increases which ultimately increase the rate of reaction.

15. Give balanced chemical equation of reaction which occur while keeping iron particles in the copper sulphate solution. What type of reaction is it?

Fe + CuSO₄ = FeSO₄ + Cu↓

It is Single displacement chemical reaction.

16. Differentiate between reactant and product.

The differences between reactant and products are:

Reactant	Products
1.     The chemical substance which takes part in chemical reaction are reactant.	The Chemical substance which is formed as a result of chemical reaction is called product.
2.     Reactant undergo chemical change.	Products are formed as a result of chemical change.
3.     Reactants are written on left hand side of the chemical equation.	Products are written on the right hand side of the chemical equation.

 

17. Write the differences between Synthesis reaction and dissociation reaction.

The differences between synthesis reaction and dissociation reaction are:

Synthesis reaction	Dissociation reaction
1.     In synthesis reaction two or more reactants combine to form a single product.	In dissociation reaction, a single reactant is broken down into two or more products.
2.     It occurs either in the presence or absence of heat, light, catalysts, etc.	It occurs in the presence of heat, light, catalyst, etc.

 

18. Compare positive and negative catalyst.

The comparison between positive catalyst and negative catalyst are as follows:

Positive catalyst	Negative catalyst
1.     It increases the rate of chemical reaction.	1.     It decreases the rate of chemical reaction.
2.     Example: iron, platinum, rhodium, etc.	2.     Example: lead, chromium, glycerine, etc.

 

20. How is catalyst differ from promotor?

Catalyst differ from promotor in the following ways:

SN	Catalyst	SN	Promotor
1	Catalyst is a chemical substance that changes the rate of chemical reaction.	1	Promotor is the chemical substance that enhances the activity of the catalyst.
2	They are categorized as positive and negative catalyst.	2	They are not categorized as positive and nega

 

21. How is endothermic reaction vary from exothermic reaction?

Endothermic reaction vary from exothermic reaction in the following ways:

SN	Endothermic reaction	SN	Exothermic reaction
1	Heat energy is absorbed by the chemical reaction from the surrounding.	1	Heat energy is released out from the chemical reaction to the surrounding.
2	There is increase in chemical potential energy at the end of the reaction.	2	There is a decrease in chemical potential at the end of the reaction.
3	Example: 2KClO3+Heat            2KCl + 3O2	3	Example: 2H2+O2          2H2O + Heat

 

 

Long Answer Questions: [4 marks each]

 

1. Write the information obtained from balanced chemical equation.

The information that are obtained from balanced chemical equation are:

i)               The names of the reactants and products and their molecular formula,

ii)             The number of atoms or molecules of reactants and products,

iii)           The ratio of weight of molecules of reactants and products.

iv)            It shows the type of chemical reaction.

2. Write the limitation of balanced chemical equation.

The limitation of balanced chemical equation are:

i)               It does not give any information about the physical state of reactants and products.

ii)             It does not tell the concentration of reactants.

iii)           It does not give any information about the rate of chemical reaction.

iv)            It does not tell whether the reaction is exothermic or endothermic.

v)             It does not tell whether the reaction is explosive or not.

vi)            It does not tell the condition under which chemical reaction occur.

3. Write the methods to increase the rate of chemical reaction.

The methods to increase the rate of chemical reaction are:

i)               By increasing the temperature of reactants.

ii)             By increasing the concentration of reactants.

iii)           By using molten or solution state of reactants.

iv)            By using catalyst along with the reactants.

v)             By increasing the pressure

4. Write the effect of concentration on the rate of chemical reaction.

The rate of chemical reaction increases on increasing the concentration of the reactants. It is because increasing the concentration of reactants increases the number of reacting molecules. This causes the higher probability of the reacting molecules to collide with each other and hence the rate of chemical reaction increases.

According to the law of mass action, the rate of chemical reaction is directly proportional to the concentration of the reactants. If the concentration of one reactant is doubled, the rate of chemical reaction will be doubled and if the concentration of both the reactants are doubled, the rate of chemical reaction will be quadrupled and so on. 

5. Describe an experiment to demonstrate that the rate of chemical reaction increases on increasing the surface area of reactants.
6.  To demonstrate that the rate of chemical reaction increases on increasing the surface area of the reactants is given below.

Two Woulfs bottle were taken and smaller granulated Zinc pieces were kept in one of the Woulf’s bottle (1 say) and large zinc pieces were kept in another Woulf’s bottle (say 2). A thistle funnel is fitted on one of the mouth of both the Woulf’s bottle. A delivery tube is fitted connected with gas jar as shown in the figure.

Dilute sulphuric acid is poured in equal quantity and the collected gas is measured at certain time.

In this reaction, it is found that the quantity of gas collected will be more in the gas jar connected with Woulf’s bottle 1.

Thus, this proves that smaller zinc pieces have more surface area of contact as compared to the larger zinc pieces.

7. Study the given word equation and answer the following equations:

Potassium Chlorate^MnO₂                                   Potassium Chloride + Oxygen

                                    ∆

a)     Express it in the form of formula equation.

The chemical equation of the above word equation is:

2KClO3                 ^MnO₂      2KCl + 3O2

                              ∆

b)    What type of chemical reaction is it?

It is a decomposition chemical reaction.

c)     What is the role of MnO₂ in the above equation?

MnO₂ in the above equation act as catalyst and it increases the rate of chemical reaction or in other words it makes the production of oxygen faster.

d)    Write any two information obtained from the above equation.

Two information obtained from the above chemical equation are:

i) Potassium chlorate is reactant where as potassium chloride and oxygen are product.

ii) Two molecules of potassium chlorate undergo decomposition to produce two molecules of potassium chloride and 3 molecules of oxygen.

38. Describe an activity to demonstrate that the rate of chemical reaction increases with the increase in the temperature of the reactants.

The following activity can demonstrate that the rate of chemical reaction increases with the increase in temperature of the reactants.

Objective: To demonstrate that the increase in temperature of the reactants.

Materials required: Tripod stand, beaker, wire gauze, burner, thermometer, glass rod.

Chemicals required: Dilute sulphuric acid, potassium permanganate solution, oxalic acid crystals, etc.

Procedure: Some oxalic acid crystals are put in two beakers and 10 ml of dilute sulphuric acid is added to each beaker. 5 ml of potassium permanganate solution is put into each beaker. The mixture is stirred with a glass rod. The solution appears dark purple. The solution in one of the beaker is heated using burner to a mild temperature at 50-60 degree Celsius.

Observation: The Purple colour of solution in the beaker changes to colourless on heating while the solution in the other beaker takes longer time to become colourless.

Conclusion: The decolourisation of the solution occur faster at high temperature. This is because increase in temperature increases the kinetic energy of the molecules of oxalic acid, potassium permanganate and dilute sulphuric acid. The energetic molecules collide with each other at faster rate breaking the bond and forming new bond to form products.