Your Progress — Chapter 10: Types of Chemical Reactions
0% complete
MCQI. Multiple Choice Questions1 mark each
Q.1 H2(g) + Cl2(g) \rightarrow 2HCl(g) is a
✓ Answer: (B) Combination Reaction
Q.2 Photolysis is a decomposition reaction caused by ___________
✓ Answer: (C) light
Q.3 A reaction between carbon and oxygen is represented by C(s) + O2(g) \rightarrow CO2(g) + Heat. In which of the type(s), the above reaction can be classified? (i) Combination Reaction (ii) Combustion Reaction (iii) Decomposition Reaction (iv) Irreversible Reaction
✓ Answer: (D) i, ii and iv
Q.4 The chemical equation Na2SO4(aq) + BaCl2(aq) \rightarrow BaSO4(s)↓ + 2NaCl(aq) represents which of the following types of reaction?
✓ Answer: (C) Precipitation
Q.5 Which of the following statements are correct about a chemical equilibrium? (i) It is dynamic in nature (ii) The rate of the forward and backward reactions are equal at equilibrium (iii) Irreversible reactions do not attain chemical equilibrium (iv) The concentration of reactants and products may be different
✓ Answer: (A) i, ii and iii
Q.6 A single displacement reaction is represented by X(s) + 2HCl(aq) \rightarrow XCl2(aq) + H2(g). Which of the following(s) could be X. (i) Zn (ii) Ag (iii) Cu (iv) Mg. Choose the best pair.
✓ Answer: (D) i and iv
Q.7 Which of the following is not an “element + element \rightarrow compound” type reaction?
✓ Answer: (C) 2CO(g) + O2(g) → 2CO2(g)
Q.8 Which of the following represents a precipitation reaction?
✓ Answer: (C) A(aq) + B(aq) → C(s) + D(aq)
Q.9 The pH of a solution is 3. Its [OH-] concentration is
✓ Answer: (C) 1 × 10^-11 M
Q.10 Powdered CaCO3 reacts more rapidly than flaky CaCO3 because of ___________.
✓ Answer: (A) large surface area
FillII. Fill in the Blanks1 mark each
| # | Statement (Answer in bold) |
|---|---|
| 1 | A reaction between an acid and a base is called neutralization. |
| 2 | When lithium metal is placed in hydrochloric acid, hydrogen gas is evolved. |
| 3 | The equilibrium attained during the melting of ice is known as physical equilibrium. |
| 4 | The pH of a fruit juice is 5.6. If slaked lime is added to this juice, its pH increases. |
| 5 | The ionic product of water at 25°C (298 K) is Kw = [H+][OH-] = 1.00 × 10^-14. |
| 6 | The normal pH of human blood is 7.35 - 7.45. |
| 7 | Electrolysis is a type of decomposition reaction. |
| 8 | The number of products formed in a synthesis reaction is one. |
| 9 | Chemical volcano is an example of decomposition reaction. |
| 10 | The ion formed by dissolution of H+ in water is called hydronium ion. |
MatchIII. Match the Following1 mark each
Refer to textbook for match answers.
T/FIV. True or False1 mark each
| # | Statement | Answer | Correction (if False) |
|---|---|---|---|
| 1 | Silver metal can displace hydrogen gas from nitric acid. | False | Silver metal cannot displace hydrogen gas from nitric acid. |
| 2 | The pH of rain water containing dissolved gases like SO3, CO2, NO2 will be less than 7. | True | |
| 3 | At the equilibrium of a reversible reaction, the concentration of the reactants and the products will be equal. | False | At equilibrium, the concentrations of reactants and products remain constant, but they need not be equal. |
| 4 | Periodical removal of one of the products of a reversible reaction increases the yield. | True | |
| 5 | On dipping a pH paper in a solution, it turns into yellow. Then the solution is basic. | False | Yellow on universal pH paper indicates an acidic solution. Neutral solution is green, and basic solution is blue/violet. |
ShortVI. Short Answer Questions2 marks each
Q.1
When an aqueous solution of potassium chloride is added to an aqueous solution of silver nitrate, a white precipitate is formed. Give the chemical equation of this reaction.
▾
✓ Answer
KCl(aq) + AgNO3(aq) -> KNO3(aq) + AgCl(s)↓
Q.2
Why does the reaction rate of a reaction increase on raising the temperature?
▾
✓ Answer
The reaction rate of a chemical reaction increases when the temperature is raised primarily because of an increase in the kinetic energy of the reactant particles. At higher temperatures, particles move faster and collide more frequently. More importantly, a larger proportion of these collisions possess sufficient energy, known as the activation energy, to overcome the energy barrier and lead to a successful reaction. Therefore, both the frequency of collisions and the fraction of effective collisions increase with temperature, resulting in an overall acceleration of the reaction rate.
Q.3
Define combination reaction. Give one example for an exothermic combination reaction.
▾
✓ Answer
A combination reaction is a reaction in which two or more reactants combine to form a single product. It is also called a synthesis reaction or composition reaction.
Example: On burning magnesium in air, it combines with oxygen to form magnesium oxide:
2Mg(s) + O2(g) -> 2MgO(s)
Example: On burning magnesium in air, it combines with oxygen to form magnesium oxide:
2Mg(s) + O2(g) -> 2MgO(s)
Q.4
Differentiate reversible and irreversible reactions
▾
✓ Answer
Reversible reaction:
i. It proceeds in both forward and backward directions under suitable conditions.
ii. Forward and backward reactions take place simultaneously.
iii. It can attain dynamic equilibrium.
iv. Reactants and products coexist; reactants are not completely converted into products. Example: N2(g) + 3H2(g) ⇌ 2NH3(g).
Irreversible reaction:
i. It proceeds essentially in one direction under the given conditions.
ii. Equilibrium is not attained.
iii. Reactants can be completely converted into products. Example: 2Mg(s) + O2(g) -> 2MgO(s).
i. It proceeds in both forward and backward directions under suitable conditions.
ii. Forward and backward reactions take place simultaneously.
iii. It can attain dynamic equilibrium.
iv. Reactants and products coexist; reactants are not completely converted into products. Example: N2(g) + 3H2(g) ⇌ 2NH3(g).
Irreversible reaction:
i. It proceeds essentially in one direction under the given conditions.
ii. Equilibrium is not attained.
iii. Reactants can be completely converted into products. Example: 2Mg(s) + O2(g) -> 2MgO(s).
LongVIII. Long Answer Questions5 marks each
Q.1
What are called thermolysis reactions?
▾
✓ Answer
Thermolysis reactions are decomposition reactions in which a reactant is decomposed by applying heat. Since the molecule dissociates by absorbing heat, the reaction is called thermolysis.
2HgO(s) --heat-> 2Hg(l) + O2(g)
2HgO(s) --heat-> 2Hg(l) + O2(g)
Q.2
Explain the types of double displacement reactions with examples.
▾
✓ Answer
Types of double displacement reactions:
(i) Precipitation reaction: Two aqueous ionic solutions react to form an insoluble salt, called a precipitate.
Pb(NO3)2(aq) + 2KI(aq) -> PbI2(s) + 2KNO3(aq)
(ii) Neutralization reaction: An acid reacts with a base to form salt and water.
HCl(aq) + NaOH(aq) -> NaCl(aq) + H2O(l)
(iii) Gas-evolution reaction: The reaction produces a gas that escapes.
Na2CO3(aq) + 2HCl(aq) -> 2NaCl(aq) + H2O(l) + CO2(g)
(i) Precipitation reaction: Two aqueous ionic solutions react to form an insoluble salt, called a precipitate.
Pb(NO3)2(aq) + 2KI(aq) -> PbI2(s) + 2KNO3(aq)
(ii) Neutralization reaction: An acid reacts with a base to form salt and water.
HCl(aq) + NaOH(aq) -> NaCl(aq) + H2O(l)
(iii) Gas-evolution reaction: The reaction produces a gas that escapes.
Na2CO3(aq) + 2HCl(aq) -> 2NaCl(aq) + H2O(l) + CO2(g)
Q.3
Explain the factors influencing the rate of a reaction
▾
✓ Answer
Important factors that affect the rate of a reaction are nature of reactants, concentration, temperature, catalyst, pressure and surface area.
(i) Nature of reactants: More reactive substances react faster. Sodium reacts faster with hydrochloric acid than with acetic acid because hydrochloric acid is stronger.
2Na(s) + 2HCl(aq) -> 2NaCl(aq) + H2(g)
(ii) Concentration: Higher concentration gives more particles per unit volume, so collisions are more frequent and the rate increases.
(iii) Temperature: Higher temperature increases kinetic energy and the number of effective collisions.
(iv) Pressure: For gaseous reactants, increased pressure brings particles closer and increases collision frequency.
(v) Catalyst: A catalyst increases reaction rate without being consumed.
(vi) Surface area: Powdered solids react faster than lumps because they have larger surface area for collisions.
(i) Nature of reactants: More reactive substances react faster. Sodium reacts faster with hydrochloric acid than with acetic acid because hydrochloric acid is stronger.
2Na(s) + 2HCl(aq) -> 2NaCl(aq) + H2(g)
(ii) Concentration: Higher concentration gives more particles per unit volume, so collisions are more frequent and the rate increases.
(iii) Temperature: Higher temperature increases kinetic energy and the number of effective collisions.
(iv) Pressure: For gaseous reactants, increased pressure brings particles closer and increases collision frequency.
(v) Catalyst: A catalyst increases reaction rate without being consumed.
(vi) Surface area: Powdered solids react faster than lumps because they have larger surface area for collisions.
Q.4
How does pH play an important role in everyday life?
▾
✓ Answer
(i) Living organisms survive only within a narrow pH range; different body fluids have characteristic pH values.
(ii) The stomach contains hydrochloric acid, with pH about 2, which helps digestion. Excess acid causes indigestion and can be neutralised by antacids.
(iii) Saliva normally has pH about 6.5 to 7.5. If mouth pH falls below 5.5, tooth enamel starts getting damaged; basic toothpastes help neutralise acids.
(iv) Soil pH is important in agriculture. Different crops need different pH ranges; citrus prefers slightly acidic to neutral soil, rice prefers acidic soil and many crops such as sugarcane prefer near-neutral soil.
(v) Unpolluted rainwater is slightly acidic, about pH 5.6, because dissolved CO2 forms carbonic acid. Polluted air containing oxides of sulphur and nitrogen makes rain more acidic, causing acid rain and harming aquatic life.
(ii) The stomach contains hydrochloric acid, with pH about 2, which helps digestion. Excess acid causes indigestion and can be neutralised by antacids.
(iii) Saliva normally has pH about 6.5 to 7.5. If mouth pH falls below 5.5, tooth enamel starts getting damaged; basic toothpastes help neutralise acids.
(iv) Soil pH is important in agriculture. Different crops need different pH ranges; citrus prefers slightly acidic to neutral soil, rice prefers acidic soil and many crops such as sugarcane prefer near-neutral soil.
(v) Unpolluted rainwater is slightly acidic, about pH 5.6, because dissolved CO2 forms carbonic acid. Polluted air containing oxides of sulphur and nitrogen makes rain more acidic, causing acid rain and harming aquatic life.
Q.5
What is a chemical equilibrium? What are its characteristics?
▾
✓ Answer
Chemical equilibrium is a state achieved in a reversible chemical reaction where the rate of the forward reaction becomes exactly equal to the rate of the backward reaction. At this point, there is no net change in the concentrations of reactants and products, and the system appears to be static. However, it is a dynamic state because both the forward and backward reactions continue to occur at the same pace. The characteristics of chemical equilibrium include: (i) The rates of the forward and backward reactions are equal. (ii) The macroscopic properties of the system, such as pressure, concentration, color, and density, remain constant over time. (iii) The equilibrium is dynamic; reactions are still occurring at the molecular level, but there is no observable change in the overall system. (iv) In the context of physical equilibrium, such as phase changes, the amounts or properties of the different phases remain constant once equilibrium is established.
HOTIX. Higher Order Thinking3 marks each
Q.1
A solid compound ‘A’ decomposes on heating into ‘B’ and a gas ‘C’. On passing the gas ‘C’ through water, it becomes acidic. Identify A, B and C.
▾
✓ Answer
CaCO3 -> CaO + CO2
CO2 + H2O -> H2CO3 (carbonic acid)
A is CaCO3, calcium carbonate. B is CaO, calcium oxide. C is CO2, carbon dioxide, which forms carbonic acid in water.
CO2 + H2O -> H2CO3 (carbonic acid)
A is CaCO3, calcium carbonate. B is CaO, calcium oxide. C is CO2, carbon dioxide, which forms carbonic acid in water.
Q.2
Can a nickel spatula be used to stir copper sulphate solution? Justify your answer.
▾
✓ Answer
A nickel spatula should not be used to stir copper sulphate solution. Nickel is more reactive than copper, so it displaces copper from CuSO4 solution and copper gets deposited on the nickel spatula.
Ni + CuSO4 -> NiSO4 + Cu
Ni + CuSO4 -> NiSO4 + Cu
NumericalVII. Numerical Problems3 marks each
Q.1
Lemon juice has a pH 2, what is the concentration of H+ ions?
▾
✓ Answer
Solution:
pH of lemon juice = 2
pH = -log10[H+]
Therefore, [H+] = 10^-2 mol L^-1
[H+] = 0.01 mol L^-1
pH of lemon juice = 2
pH = -log10[H+]
Therefore, [H+] = 10^-2 mol L^-1
[H+] = 0.01 mol L^-1
Q.2
Calculate the pH of 1.0 \times 10-4 molar solution of HNO3.
▾
✓ Answer
Solution:
[H+] = 1.0 x 10^-4 M
pH = -log10[H+]
= -log10(1.0 x 10^-4)
= 4
[H+] = 1.0 x 10^-4 M
pH = -log10[H+]
= -log10(1.0 x 10^-4)
= 4
Q.3
What is the pH of 1.0 \times 10-5 molar solution of KOH?
▾
✓ Answer
Solution:
KOH(aq) -> K+(aq) + OH-(aq)
[OH-] = 1 x 10^-5 mol L^-1
pOH = -log10[OH-] = 5
pH + pOH = 14
pH = 14 - 5 = 9
KOH(aq) -> K+(aq) + OH-(aq)
[OH-] = 1 x 10^-5 mol L^-1
pOH = -log10[OH-] = 5
pH + pOH = 14
pH = 14 - 5 = 9
Q.4
The hydroxide ion concentration of a solution is 1 \times 10-11M. What is the pH of the solution?
▾
✓ Answer
Solution:
[OH-] = 1 x 10^-11 M
pOH = -log10[OH-] = 11
pH + pOH = 14
pH = 14 - 11 = 3
[OH-] = 1 x 10^-11 M
pOH = -log10[OH-] = 11
pH + pOH = 14
pH = 14 - 11 = 3
🎒 Brain Grain Revision Challenge
Study Smarter, Score Higher.
Revise this Samacheer Class 10 Science topic, then continue with the Revision Challenge.
Free Revision
Daily Revision
Exam Practice
XP Challenge
AI Doubt Help
🏆
Revision Challenge
← Previous
Ch.9 Solutions