Annual Examination – Set 3 വാർഷിക പരീക്ഷ
A full annual-examination paper covering all eight chapters (Part 1 and Part 2). Print it on A4 paper and give it to the student with a timer; the answer key is printed separately.
ANNUAL EXAMINATION · MODEL PAPER · SET 3
Standard IX · CHEMISTRY രസതന്ത്രം
Name:Roll No.:Division:
- The first 15 minutes is cool-off time. Use it to read the questions and plan your answers; do not write during this time.
- Answer all the questions. The score for each question is shown in brackets on the right.
- Read each question carefully before you answer. Answer in keeping with the score and the time.
- Write balanced chemical equations and correct formulae. Show the steps for calculations (mass, mass percentage, oxidation number).
- Draw neat, labelled diagrams wherever needed. Use the data (atomic numbers, masses, electronegativities) given in the questions.
Section AAnswer all questions · 10 × 1 = 10 marks
1.
The mass of an electron is about
[1](a) 1837 times the mass of a proton(b) 1/1837 of the mass of a proton(c) equal to the mass of a proton(d) equal to the mass of a neutron
2.
Find the relation and fill in: iodine-131 : study and treatment of the thyroid gland :: iron-59 :
[1]3.
Lanthanum (Z = 57) and the 14 elements that come after it are placed in a separate row below the periodic table. They are called
[1](a) actinoids(b) transition elements(c) lanthanoids(d) noble gases
4.
The basicity of phosphoric acid, H3PO4, is
[1](a) 1(b) 2(c) 3(d) 4
5.
Pick the odd one out and give the reason: NaOH, KOH, HNO3, Ca(OH)2
[1]6.
Raising the temperature increases the rate of a reaction mainly because
[1](a) the threshold energy becomes lower(b) more particles get kinetic energy equal to or greater than the threshold energy(c) the number of reactant particles increases(d) the surface area of the reactants increases
7.
State whether true or false. If false, correct it: “A catalyst is used up in the reaction that it speeds up.”
[1]8.
A torch beam is passed through four glasses in a dark room. In which glass will the path of the light be seen?
[1](a) salt solution(b) sugar solution(c) kanji vellam (rice water)(d) copper sulphate solution
9.
The main component of natural gas, used as CNG in autorickshaws and buses, is
[1](a) butane(b) methane(c) propane(d) ethene
10.
Find the relation and fill in: kerosene : C10–C16 :: diesel :
[1]Section BAnswer all questions · 8 × 2 = 16 marks
11.
J. J. Thomson found the charge-to-mass ratio (e/m) of the electron to be 1.76 × 1011 C/kg. Robert Millikan’s oil-drop experiment gave the charge of the electron as 1.6 × 10−19 C.
(a) Find the mass of an electron.
(b) About how many electrons, taken together, have the same mass as one proton? Why is the mass of the electrons not counted in the mass number?
[2](a) Find the mass of an electron.
(b) About how many electrons, taken together, have the same mass as one proton? Why is the mass of the electrons not counted in the mass number?
12.
Look at this list of compounds: ferrous sulphate crystals (FeSO4·7H2O), sodium chloride (NaCl), potassium dichromate (K2Cr2O7), magnesium chloride (MgCl2), cobalt nitrate (Co(NO3)2), calcium carbonate (CaCO3).
(a) Which of them would you expect to be coloured? Give the reason.
(b) In which groups are the transition elements placed, and from which period do they begin?
[2](a) Which of them would you expect to be coloured? Give the reason.
(b) In which groups are the transition elements placed, and from which period do they begin?
13.
Milk of magnesia contains magnesium hydroxide, Mg(OH)2. It neutralises the hydrochloric acid in the stomach.
(a) Write the ions given by magnesium hydroxide and by hydrochloric acid.
(b) Write the formula of the salt formed, showing the criss-cross steps, and write the balanced equation for the reaction.
[2](a) Write the ions given by magnesium hydroxide and by hydrochloric acid.
(b) Write the formula of the salt formed, showing the criss-cross steps, and write the balanced equation for the reaction.
14.
Find the oxidation number of (a) chlorine in potassium chlorate, KClO3 (b) nitrogen in sodium nitrite, NaNO2. Show the working.
[2]15.
In a teacher demonstration, a little solid zinc sulphate is mixed with solid barium nitrate in a dry test tube. Nothing seems to happen. When solutions of the two are mixed, a white precipitate forms at once.
(a) Name the factor that affects the rate here. Why do the solutions react at once but the solids do not?
(b) Complete and balance: ZnSO4 + Ba(NO3)2 → ______ + ______ . Name the type of the reaction.
[2](a) Name the factor that affects the rate here. Why do the solutions react at once but the solids do not?
(b) Complete and balance: ZnSO4 + Ba(NO3)2 → ______ + ______ . Name the type of the reaction.
16.
Write why each of these is added to food or drinks: (a) sodium benzoate (b) allyl hexanoate (c) indigo carmine (d) vanillin
[2]17.
Two bottles P and Q contain white powders: one is potassium chloride and the other potassium carbonate. Solutions of both are made.
(a) When barium chloride solution is added, Q gives a white precipitate but P does not. Dilute hydrochloric acid is then added to the precipitate. What will you see, and what is Q?
(b) How will you confirm that P is a chloride? Write the equation.
[2](a) When barium chloride solution is added, Q gives a white precipitate but P does not. Dilute hydrochloric acid is then added to the precipitate. What will you see, and what is Q?
(b) How will you confirm that P is a chloride? Write the equation.
18.
Petrol (C5–C10) is a mixture of hydrocarbons. Its calorific value in Fig 7.2 is given as that of octane, the alkane with 8 carbon atoms.
(a) Using the general formula, find the number of hydrogen atoms in a molecule of octane. Write its molecular formula.
(b) Find the number of hydrogen atoms in decene, the 10-carbon alkene. Write its molecular formula.
[2](a) Using the general formula, find the number of hydrogen atoms in a molecule of octane. Write its molecular formula.
(b) Find the number of hydrogen atoms in decene, the 10-carbon alkene. Write its molecular formula.
Section CAnswer all questions · 6 × 3 = 18 marks
19.
The figure shows the orbit diagrams of three atoms X, Y and W. Only the number of neutrons is written in each nucleus.
(a) Find the atomic number and the mass number of each atom.
(b) Which two are isotopes and which two are isobars? Give the reasons.
(c) One of the isotopes is radioactive and is used to find the age of fossils; the other is used to study life processes in plants and animals. Name both.
[3](a) Find the atomic number and the mass number of each atom.
(b) Which two are isotopes and which two are isobars? Give the reasons.
(c) One of the isotopes is radioactive and is used to find the age of fossils; the other is used to study life processes in plants and animals. Name both.
20.
Nitrogen (Z = 7) combines with hydrogen (Z = 1) to form ammonia, NH3.
(a) Draw the electron dot diagram of a molecule of ammonia.
(b) What is the valency of nitrogen in ammonia? Explain using the diagram.
(c) Using this valency of nitrogen, write the formula of calcium nitride, the compound of calcium (Z = 20) and nitrogen. Show the steps.
[3](a) Draw the electron dot diagram of a molecule of ammonia.
(b) What is the valency of nitrogen in ammonia? Explain using the diagram.
(c) Using this valency of nitrogen, write the formula of calcium nitride, the compound of calcium (Z = 20) and nitrogen. Show the steps.
21.
Write the oxidation number of every atom above its symbol and find out whether each is a redox reaction.
(a) 2KI + Cl2 → 2KCl + I2
(b) BaCl2 + Na2SO4 → BaSO4 + 2NaCl
(c) For the redox reaction, name the element oxidised, the element reduced, the oxidising agent and the reducing agent.
[3](a) 2KI + Cl2 → 2KCl + I2
(b) BaCl2 + Na2SO4 → BaSO4 + 2NaCl
(c) For the redox reaction, name the element oxidised, the element reduced, the oxidising agent and the reducing agent.
22.
In a teacher demonstration, equal lengths (equal masses) of magnesium ribbon are dropped into two flasks of hydrochloric acid – one concentrated and one dilute. The acid is in excess both times. The hydrogen formed is collected and its volume is measured every minute: Mg + 2HCl → MgCl2 + H2↑. The graph shows the results.
(a) Which curve, A or B, is for the concentrated acid? Explain using collisions.
(b) From the graph, find the volume of hydrogen formed in the first minute in A and in B.
(c) In which part of each curve is the reaction fastest? Why do both curves finally become flat at the same volume?
[3](a) Which curve, A or B, is for the concentrated acid? Explain using collisions.
(b) From the graph, find the volume of hydrogen formed in the first minute in A and in B.
(c) In which part of each curve is the reaction fastest? Why do both curves finally become flat at the same volume?
23.
In a teacher demonstration in a fume cupboard, two gas jars A and B are filled with dry chlorine. A dry coloured cloth is hung in A and a moist coloured cloth of the same colour in B.
(a) In which jar does the cloth lose its colour? Why does the other cloth keep its colour?
(b) Write the equations that explain the bleaching.
(c) Is the coloured substance in the cloth oxidised or reduced? Give one use of chlorine that depends on this property.
[3](a) In which jar does the cloth lose its colour? Why does the other cloth keep its colour?
(b) Write the equations that explain the bleaching.
(c) Is the coloured substance in the cloth oxidised or reduced? Give one use of chlorine that depends on this property.
24.
The petrol fraction of petroleum contains the alkane with 5 carbon atoms.
(a) Write its molecular formula and IUPAC name.
(b) Draw its structural formula.
(c) Balance the equation for its complete burning: C5H12 + O2 → CO2 + H2O. How does burning more and more petrol add to global warming?
[3](a) Write its molecular formula and IUPAC name.
(b) Draw its structural formula.
(c) Balance the equation for its complete burning: C5H12 + O2 → CO2 + H2O. How does burning more and more petrol add to global warming?
Section DAnswer all questions · 4 × 4 = 16 marks
25.
For the school science fair, Anu’s group made a bar chart of the approximate atomic radii of the elements of period 3 (argon, a noble gas, is left out).
(a) How does the size of the atoms change from sodium to chlorine? Explain the reason.
(b) Classify these seven elements as metals, metalloid and non-metals. Where are the metals and the non-metals placed in the periodic table?
(c) Potassium (2, 8, 8, 1) is just below sodium in group 1. Is a potassium atom larger or smaller than a sodium atom? Why?
(d) Which is larger: a potassium atom or a calcium atom (2, 8, 8, 2)? Where in the periodic table are the largest atoms found?
[4](a) How does the size of the atoms change from sodium to chlorine? Explain the reason.
(b) Classify these seven elements as metals, metalloid and non-metals. Where are the metals and the non-metals placed in the periodic table?
(c) Potassium (2, 8, 8, 1) is just below sodium in group 1. Is a potassium atom larger or smaller than a sodium atom? Why?
(d) Which is larger: a potassium atom or a calcium atom (2, 8, 8, 2)? Where in the periodic table are the largest atoms found?
26.
Coconut and arecanut farmers in Kerala spray Bordeaux mixture (copper sulphate + lime) on their palms. To check whether enough lime has been added, the farmer dips a clean iron knife into the mixture. If a reddish-brown coating forms on the knife, more lime is needed. The coating forms by this reaction:
Fe + CuSO4 → FeSO4 + Cu (CuSO4 contains Cu2+ and SO42− ions; FeSO4 contains Fe2+ and SO42− ions.)
(a) Using the atomic masses Fe = 56, Cu = 64, S = 32, O = 16, find the total mass of the reactants and of the products (in u). Which law does this show?
(b) Find the oxidation number of sulphur in CuSO4 and in FeSO4.
(c) Write the oxidation numbers of iron and copper before and after the reaction. Which is oxidised and which is reduced?
(d) Name the oxidising agent and the reducing agent. Is this a redox reaction? Why?
[4]Fe + CuSO4 → FeSO4 + Cu (CuSO4 contains Cu2+ and SO42− ions; FeSO4 contains Fe2+ and SO42− ions.)
(a) Using the atomic masses Fe = 56, Cu = 64, S = 32, O = 16, find the total mass of the reactants and of the products (in u). Which law does this show?
(b) Find the oxidation number of sulphur in CuSO4 and in FeSO4.
(c) Write the oxidation numbers of iron and copper before and after the reaction. Which is oxidised and which is reduced?
(d) Name the oxidising agent and the reducing agent. Is this a redox reaction? Why?
27.
After the floods, a relief camp was set up in a school in Aluva.
• The water drawn from a nearby well was muddy. When it was left to stand, the mud settled; when it was filtered, mud was left on the filter paper.
• The filtered water looked clear, but when a torch beam was passed through a glass of it in a dark room, the path of the light could still be seen faintly.
• ORS solution made from packets was clear, and the path of the torch beam could not be seen in it.
• Kanji vellam (rice water) was served to the children.
(a) Is the muddy well water a true solution, a colloid or a suspension? Give two reasons.
(b) What does the faint path of light in the filtered water show? Name this effect and give the particle size of such particles.
(c) Is ORS solution a true solution, a colloid or a suspension? Write two properties of its particles.
(d) Kanji vellam is a colloid. Name its type, its dispersed phase and its dispersion medium.
[4]• The water drawn from a nearby well was muddy. When it was left to stand, the mud settled; when it was filtered, mud was left on the filter paper.
• The filtered water looked clear, but when a torch beam was passed through a glass of it in a dark room, the path of the light could still be seen faintly.
• ORS solution made from packets was clear, and the path of the torch beam could not be seen in it.
• Kanji vellam (rice water) was served to the children.
(a) Is the muddy well water a true solution, a colloid or a suspension? Give two reasons.
(b) What does the faint path of light in the filtered water show? Name this effect and give the particle size of such particles.
(c) Is ORS solution a true solution, a colloid or a suspension? Write two properties of its particles.
(d) Kanji vellam is a colloid. Name its type, its dispersed phase and its dispersion medium.
28.
Rockets designed at the Vikram Sarabhai Space Centre (VSSC), Thumba, Thiruvananthapuram, have a cryogenic stage that burns liquid hydrogen with liquid oxygen carried in the rocket.
(a) Write the balanced equation for the burning of hydrogen. Using H = 1 and O = 16, find the mass of oxygen needed to burn 2 kg of hydrogen.
(b) The calorific value of hydrogen is 143 kJ/g. How much heat is released when 2 kg of hydrogen burns completely?
(c) Oxygen itself does not burn. Why must the rocket still carry oxygen?
(d) On its way up, the rocket passes through the ozone layer in the stratosphere. How is ozone formed from oxygen there, and why is the ozone layer important?
[4](a) Write the balanced equation for the burning of hydrogen. Using H = 1 and O = 16, find the mass of oxygen needed to burn 2 kg of hydrogen.
(b) The calorific value of hydrogen is 143 kJ/g. How much heat is released when 2 kg of hydrogen burns completely?
(c) Oxygen itself does not burn. Why must the rocket still carry oxygen?
(d) On its way up, the rocket passes through the ozone layer in the stratosphere. How is ozone formed from oxygen there, and why is the ozone layer important?
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