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Class 10 Chemistry Chapter 17 Reaction Kinetics Full Unit Test 8
10th Class Chemistry Chapter 17 solved Model Paper
Prepare for your matric Chemistry examination with the Class 10 Chemistry Chapter 17: Reaction Kinetics Full Unit Test 2027, part of the Punjab Board 2027 Model Papers series. This Class 10 Chemistry Full Unit Test covers the complete unit on Reaction Kinetics and helps students revise important concepts, practise exam-style questions, and assess their preparation according to the Punjab Board syllabus. Students can use this chapter-wise Chemistry test for revision, self-assessment, and effective examination preparation. Visit 786Times.com for more Class 10 Chemistry model papers, chapter-wise tests, important questions, and educational resources to support your Punjab Board examination preparation.
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Full Chapter Test
T-8
CHAPTER # 17
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Note:Four possible answers A, B, C and D to each question are given. The choice which you think is correct, fill that circle in front of that question with Marker or Pen ink. Cutting or filling two or more circles will result in zero mark in that question.
1.
Increasing the concentration of reactants will:
(a) decrease collisions(b) increase effective collisions(c) stop reaction(d) decrease kinetic energy
Answer: (b) increase effective collisions
2.
Increasing temperature increases reaction rate because:
(a) Volume decreases(b) Number of molecules decreases(c) Frequency and energy of collisions increase(d) Activation energy becomes zero
Answer: (c) Frequency and energy of collisions increase
3.
Which type of reaction releases heat energy to the surroundings?
(a) Endothermic reaction(b) Neutral reaction(c) Exothermic reaction(d) Reversible reaction
Answer: (c) Exothermic reaction
4.
If the temperature of a reaction increases by 20°C, the rate of reaction will approximately:
(a) Become half(b) Double(c) Become four times faster(d) Remain the same
Answer: (c) Become four times faster
5.
In reactions involving gases, the rate can be increased by:
(a) Reducing pressure(b) Increasing pressure(c) Reducing temperature(d) Using smaller containers
Answer: (b) Increasing pressure
6.
Why do finely divided solids react faster than large pieces due to?
(a) higher mass(b) larger surface area(c) lower density(d) colder
Answer: (b) larger surface area
7.
Enzymes are:
(a) Chemical catalysts(b) Biological catalysts(c) Metals(d) Acids
Answer: (b) Biological catalysts
8.
Food ripening mainly occurs due to reactions involving:
(a) Acids(b) Metals(c) Enzymes(d) Salts
Answer: (c) Enzymes
9.
Food scientists study reaction rates mainly to:
(a) Increase food prices(b) Minimize food spoilage(c) Reduce farming land(d) Increase food colour only
Answer: (b) Minimize food spoilage
10.
The number of collisions per unit volume of the reaction mixture is called:
(a) Collision energy(b) Activation energy(c) Collision frequency(d) Collision force
Answer: (c) Collision frequency
11.
Which of the following explains the increase in rate of reaction in the presence of a catalyst?
(a) Catalyst provides extra energy to the reactant molecules(b) Catalyst provides an alternative pathway which lowers the activation energy.(c) Catalyst increases the collision frequency.(d) Catalyst decreases the collision frequency.
Answer: (b) Catalyst provides an alternative pathway which lowers the activation energy.
12.
When a reaction proceeds ahead, how the concentrations of reactants and products change?
(a) Concentration of reactants increases and that of the products decreases.(b) Concentration of reactants decreases and that of the products increases.(c) Concentration of both reactants and products decreases.(d) Concentration of both reactants and products increases.
Answer: (b) Concentration of reactants decreases and that of the products increases.
Here is the SUBJECTIVE Type Paper for 10th Class.
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Part – I
Marks: 48
CHEMISTRY (SUBJECTIVE TYPE)
Time: 1:45 minute
2.Write short answers to any Five (5) questions:[5×2=10]
(i)
Define collision theory.
A reaction occurs only when reactant particles collide with energy equal to or greater than the activation energy and with the proper orientation; the rate depends on the number of effective collisions per second.
(ii)
Define activation energy.
The minimum energy that reactant particles must possess to start a chemical reaction (symbol Ea).
(iii)
State the law of conservation of mass.
Mass can neither be created nor destroyed in a chemical reaction; the total mass of reactants equals the total mass of products.
(iv)
What is an endothermic reaction? Give example.
A reaction that absorbs heat from the surroundings (ΔH is positive). Example: CaCO3 → CaO + CO2 on heating.
(v)
Why is high temperature used while cooking food?
High temperature gives the particles more energy and more frequent collisions, so the cooking reactions are faster and the food cooks in less time.
(vi)
How does increasing the concentration of reactants affect the rate of reaction?
More particles per unit volume means more collisions per second, so more effective collisions occur and the rate increases.
(vii)
Why is the initial rate of reaction fast and final is slow?
At the start the concentration of reactants is highest, giving many collisions; as reactants are used up their concentration falls, collisions decrease and the rate slows down.
(viii)
Define a catalyst. Give example.
A substance that changes the rate of a reaction without being used up. Example: MnO2 in the decomposition of KClO3; Pt in the addition of H2 to ethene.
3.Write short answers to any Five (5) questions:[5×2=10]
(i)
How can measure gas produce when HCI react with lime stone?
CaCO3 + 2HCl CaCl2 + H2O + CO2. Collect the CO2 in a gas syringe (or an inverted measuring cylinder over water) and note its volume at regular time intervals; alternatively measure the loss of mass on a balance.
(ii)
What is the importance of studying reaction rates in the food industry?
It helps find the best conditions to slow spoilage, increase shelf life, control ripening and storage, and reduce food waste.
(iii)
How can understanding enzymatic reactions help prevent food spoilage?
Enzymes cause food to ripen and rot. Knowing how they work lets us slow or stop them (cooling, freezing, heating to destroy enzymes, changing pH), so food stays fresh longer.
(iv)
How spoilage of butter can be prevented? Give an example.
Butter turns rancid by reaction with air and by microbes/enzymes. It is prevented by keeping it at low temperature, e.g. storing it in a refrigerator in an airtight wrapper.
(v)
Why a catalyst is mostly used in finely divided form?
Fine powder has a larger surface area, so more reactant particles contact the catalyst at once and the reaction is faster.
(vi)
How does the concentrations of the products change during reaction? Explain with the help of a graph.
The product concentration rises quickly at first (reactant concentration is high), then more slowly, and finally becomes constant when the reactants are used up.
(vii)
Why some fruits and vegetables get destroyed early during summer than during winter.
The higher temperature in summer speeds up the enzymatic and microbial reactions that spoil them, while in winter these reactions are slow.
(viii)
What is a successful collision?
A collision in which the particles have energy ≥ Ea and the correct orientation, so that products are formed.
4.Write short answers to any Five (5) questions:[5×2=10]
(i)
Why does the burning of sulphur proceed slower in air than in pure oxygen?
Air contains only about 21% oxygen, so O2 concentration is lower and collisions with sulphur are fewer; pure oxygen has a higher concentration, so burning is faster.
(ii)
Why is the rate of a reaction often very fast at the beginning of the reaction?
Because the concentration of reactants is highest at the start, giving the maximum number of collisions per second.
(iii)
Magnesium does not react with air at room temperature but reacts very fast at high temperature giving intense white light. Explain.
At room temperature the particles do not have energy equal to Ea, so collisions are not effective. On heating they gain enough energy and burn rapidly: 2Mg + O2 2MgO, giving heat and intense white light.
(iv)
Give any two features of the catalytic action of an enzyme.
- Highly specific: the active site fits only a particular substrate.
- Works at an optimum temperature and pH, and is not used up.
(v)
In what different ways you can increase the successful collisions between the particles of the reactants?
By increasing the temperature, the concentration (or pressure for gases) and the surface area of solids, and by adding a suitable catalyst.
(vi)
From where do molecules get energy to attain higher energy state?
From the surroundings: by absorbing heat and from collisions with other fast-moving molecules; light can also supply energy.
(vii)
How does the presence of V2O5 catalyst lower the activation energy of the following reaction?
2 SO2(g) +O2(g) 2 SO3(g)
V2O5 provides an alternative pathway: SO2 is oxidised on its surface to SO3 and the catalyst is then regenerated. This path needs less energy, so the activation energy is lowered and more molecules react.
(viii)
Part – II
Explain the catalytic action of an enzyme.
The substrate fits into the enzyme’s active site (lock-and-key) forming an enzyme-substrate complex, which lowers the activation energy; the products are released and the enzyme is free to act again.
NOTE:- Attempt any two questions.[9×2=18]
5.
(a) Discuss the change in temperature of a chemical reaction.
- Rate increases with temperature; for many reactions it roughly doubles for each 10°C rise.
- Particles move faster, collide more often and with greater energy.
- More particles have energy ≥ Ea, so more effective collisions occur.
- Exothermic reactions release heat (temperature rises) and endothermic reactions absorb heat (temperature falls).
(b) Explain effect of concentration on the rate of reaction.
- Higher concentration means more particles per unit volume.
- Collision frequency increases, so effective collisions per second increase.
- Rate increases; example: coal burns faster in pure oxygen than in air, limestone reacts faster with concentrated HCl.
6.
(a) Explain effect of surface area of solid on rate of chemical reaction.
- Only surface particles of a solid can collide with the other reactant.
- Powdering the solid greatly increases surface area, exposing more particles.
- More collisions per second, so the reaction is faster. Example: powdered marble reacts with HCl faster than a marble chip.
(b) Explain effect of temperature on rate of chemical reaction.
- Higher temperature raises the kinetic energy and speed of particles.
- Collisions are more frequent and more of them have energy ≥ Ea.
- Rate roughly doubles for every 10°C rise; example: food spoils faster in warm weather.
7.
(a) Explain the effect of catalyst on the rate of reaction.
- A catalyst changes the rate without being used up.
- It provides an alternative path with lower activation energy, so more particles can react.
- It does not change the products or ΔH. Example: V2O5 in making SO3; Pt in hydrogenation.
(b) Write briefly about the role enzymes play in our body as biological catalysts.
- Enzymes are protein catalysts made by living cells.
- They speed up digestion, respiration and other body reactions by lowering activation energy.
- Each is specific (lock-and-key), works at body temperature and optimum pH, and is not used up.
- Examples: amylase digests starch; pepsin digests proteins.
