Model Test Paper മാതൃകാ ചോദ്യപേപ്പർ
A full paper in the Kerala Class 9 Chemistry pattern, covering the whole of “Chemical Kinetics” – the signs of a chemical change, the four types of chemical reactions, balancing and classifying equations, the rate of reaction, collision theory and threshold energy, the five factors that affect the rate, catalysts and enzymes, and reading a volume–time graph. Work on paper with a timer before you look at the solutions.
Standard IX · Chemistry
Chapter 5 · രാസഗതികം · Chemical Kinetics
- The first 15 minutes are cool-off time: read every question and plan your answers; do not write.
- Answer all questions. Marks for each question are shown on the right.
- Balance equations by changing only the coefficients. Name the type of a reaction in full (for example, “double decomposition”).
- When asked to explain, use collision theory: effective collisions and threshold energy.
SECTION AAnswer all · 8 × 1 = 8 marks
1.
Which of the following is a chemical change?
(1)(a) melting of ice(b) dissolving sugar in water(c) milk turning into curd(d) boiling of water
2.
When sodium hydroxide solution is added to blue copper sulphate solution, a blue solid forms and settles at the bottom of the test tube: CuSO4 + 2NaOH → Cu(OH)2↓ + Na2SO4. An insoluble solid formed like this in a reaction is called a .
(1)3.
Find the relation and fill in: C + O2 → CO2 : combination :: 2HgO → 2Hg + O2 :
(1)4.
The reaction Mg + 2HCl → MgCl2 + H2↑ is an example of
(1)(a) combination(b) decomposition(c) displacement(d) double decomposition
5.
The minimum kinetic energy that the reactant particles must have to change into products is called .
(1)6.
Which of these will not make magnesium ribbon react faster with hydrochloric acid?
(1)(a) warming the acid(b) using magnesium powder(c) adding water to the acid(d) using concentrated acid
7.
Which of these reactions is the fastest?
(1)(a) rusting of an iron gate(b) weathering of rocks(c) bursting of a firecracker(d) ripening of a mango
8.
The enzyme in our saliva that speeds up the breakdown of starch into maltose is .
(1)SECTION BAnswer all · 5 × 2 = 10 marks
9.
While whitewashing, water is poured on quicklime (നീറ്റുകക്ക). The mixture hisses and becomes very hot: CaO + H2O → Ca(OH)2. (a) Which type of reaction is this? Give the reason.
(b) Which sign of a chemical change is seen here? What is such a reaction called?
(2)(b) Which sign of a chemical change is seen here? What is such a reaction called?
10.
Barium chloride solution is added to sodium sulphate solution: BaCl2 + Na2SO4 → BaSO4↓ + 2NaCl. (a) Name the type of reaction and the visible sign seen.
(b) Which ions exchange partners in this reaction?
(2)(b) Which ions exchange partners in this reaction?
11.
In a balloon filled with hydrogen and oxygen, the molecules collide with each other millions of times every second, yet nothing happens until a spark is given. (a) According to collision theory, when does a chemical reaction take place?
(b) Why do the gases not react without the spark?
(2)(b) Why do the gases not react without the spark?
12.
At Neendakara harbour, fishermen pack the fish in crushed ice as soon as it is unloaded from the boats. (a) Which factor affecting the rate of reaction is used here?
(b) Explain, using kinetic energy and threshold energy, how this keeps the fish fresh for longer.
(2)(b) Explain, using kinetic energy and threshold energy, how this keeps the fish fresh for longer.
13.
A sugar cube does not catch fire when a burning match is held to it. But when a little ash is rubbed on it, it burns. After burning, the ash is still left behind. (a) What is the role of the ash?
(b) What does the ash left behind tell you about it?
(2)(b) What does the ash left behind tell you about it?
SECTION CAnswer all · 4 × 3 = 12 marks
14.
Study the three reactions and write, for each, (i) the sign that shows a chemical change has taken place and (ii) the type of the reaction.
(3)| What is done and seen | Equation | |
|---|---|---|
| (a) | A zinc strip is dipped in blue copper sulphate solution. The blue colour fades and a reddish-brown layer forms on the zinc. | Zn + CuSO4 → ZnSO4 + Cu |
| (b) | Potassium hydroxide solution is mixed with dilute nitric acid. The test tube becomes warm. | KOH + HNO3 → KNO3 + H2O |
| (c) | Dilute hydrochloric acid is poured on washing soda (sodium carbonate). It fizzes. | Na2CO3 + 2HCl → 2NaCl + H2O + CO2↑ |
15.
Balance the equations and name the type of each reaction. (a) Al + Fe2O3 → Al2O3 + Fe (thermite, used to weld rails)
(b) Fe + Cl2 → FeCl3
(c) NaHCO3 → Na2CO3 + H2O + CO2 (baking soda heated in a cake)
(3)(b) Fe + Cl2 → FeCl3
(c) NaHCO3 → Na2CO3 + H2O + CO2 (baking soda heated in a cake)
16.
Marble chips are added to dilute hydrochloric acid (taken in excess) and the carbon dioxide formed is collected in a gas syringe: CaCO3 + 2HCl → CaCl2 + H2O + CO2↑. The readings are given in the table and the graph.
(a) How much CO2 forms in the 1st minute and in the 4th minute? In which minute is the reaction fastest? Why?
(b) Why does the volume stop changing after 5 minutes?
(c) The experiment is repeated with the same mass of marble powder. How will the graph change? Give the reason.
(3)| Time (minutes) | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|
| Volume of CO2 (mL) | 0 | 36 | 60 | 76 | 86 | 90 | 90 |
(b) Why does the volume stop changing after 5 minutes?
(c) The experiment is repeated with the same mass of marble powder. How will the graph change? Give the reason.
17.
Give the scientific reason, and name the factor that affects the rate in each case. (a) Fireworks contain magnesium powder, not magnesium ribbon.
(b) A glowing incense stick bursts into flame when it is put into a jar of pure oxygen.
(c) Potassium reacts violently with cold water, but water can be stored in a copper vessel for years.
(3)(b) A glowing incense stick bursts into flame when it is put into a jar of pure oxygen.
(c) Potassium reacts violently with cold water, but water can be stored in a copper vessel for years.
SECTION DAnswer all · 2 × 5 = 10 marks
18.
Read the passage and answer the questions.
(b) What is the role of V2O5? What will you find about its amount and its chemical nature at the end?
(c) What does the sign ⇌ tell you about this reaction?
(d) How do the pressure (2 atm) and the temperature (720 K) help the reaction to go faster?
(e) Write the balanced equation for the Haber process and name its catalyst. Where in Kerala is this reaction used on a large scale?
(5)Sulphuric acid is one of the most important industrial chemicals; fertiliser factories need it in large amounts. It is made by the contact process (സമ്പർക്ക പ്രക്രിയ). Its main step is 2SO2(g) + O2(g) V2O5⇌ 2SO3(g) carried out with vanadium pentoxide (V2O5) at a pressure of 2 atm and a temperature of 720 K.
(a) Which type of reaction is this? Give the reason.(b) What is the role of V2O5? What will you find about its amount and its chemical nature at the end?
(c) What does the sign ⇌ tell you about this reaction?
(d) How do the pressure (2 atm) and the temperature (720 K) help the reaction to go faster?
(e) Write the balanced equation for the Haber process and name its catalyst. Where in Kerala is this reaction used on a large scale?
19.
Read the passage and answer the questions.
(b) Name the factor that makes the batter rise faster in April. Where should grandmother keep the batter on a cool July evening so that it is ready by morning?
(c) What are enzymes? Name one enzyme in your body and the change it speeds up.
(d) Why does a split log catch fire faster than a whole log? Explain using collisions.
(e) Why do the flames become bright when air is blown into the fire? Name the factor.
(5)Ammu lives in Thrissur with her grandmother, who still cooks on a firewood hearth. In the evening grandmother grinds soaked rice and urad dal into a batter for the next morning’s idli and dosa. In the hot days of April the batter rises and smells sour by morning; in the cool, rainy days of July it takes much longer; and batter kept in the refrigerator hardly changes at all. The batter rises (ferments) because tiny microbes in it produce enzymes. To light the hearth quickly, grandmother never puts in a whole log – she splits it into thin sticks. When the fire is weak she blows air into it through a metal blowpipe, and the flames at once become bright.
(a) Burning of firewood is a chemical change. Write two observations that show this.(b) Name the factor that makes the batter rise faster in April. Where should grandmother keep the batter on a cool July evening so that it is ready by morning?
(c) What are enzymes? Name one enzyme in your body and the change it speeds up.
(d) Why does a split log catch fire faster than a whole log? Explain using collisions.
(e) Why do the flames become bright when air is blown into the fire? Name the factor.
*** End of the question paper ***