CONTEST 22
ROUND 1
1. A mixture of mercurous and mercuric nitrates were added to a food substance. A white precipitate
formed which on gentle heating turned red. Name the food substance that was tested.
ANSWER: Protein
2. A carbohydrate solution was boiled with Fehling’s solution A and B and a brick red precipitate was
formed. Name the type of carbohydrate that was tested.
ANSWER: Reducing sugar (Monosaccharide)
3. Sodium hydroxide solution was added to a food substance. Copper sulphate was then added to
provide positive results. . Name the food substance that was tested.
ANSWER: Protein
4. Find the real depth of an object in a liquid with refractive index when the apparent depth of the object is
ANSWER:
5. A coin lies at the bottom of a vessel containing liquid with refractive index to a depth of . Find the
apparent depth of the coin.
ANSWER:
6. Find the refractive index of a thick glass block if the apparent depth of an object in contact with it is
ANSWER:
7. State the expected observation when an alkanoic acid is tested with NaHCO 3 solution and explain the
chemistry of the test.
ANSWER: Effervescence is observed
Chemistry: The alkanoic acid protonates the HCO3- ion to give H2CO3 which
decomposes to CO2 gas and H2O
8. Give the expected product when butanoic acid is treated with a hot solution of ammonia.
ANSWER: Ammonium butanoate
9. State the expected observation when methyl butanoate is treated with a dilute solution of NaOH and
the mixture heated. Explain the chemistry of the observation.
ANSWER: The sweet smell of methyl butanoate (an ester) disappears when treated
with hot NaOH solution.
Chemistry: Methyl butanoate is an ester and is hydrolyzed by the alkali (to
give butanoate ion and methanol)
PREAMBLE: Find the solution set of the inequality 3x – 3 > 15 given that:
10. x is an integer strictly between 1 and 10.
ANSWER: {7, 8, 9}
[ 3x – 3 > 15, 3x > 18, x > 6, hence {7, 8, 9}
11. x is an integer between 1 and 10 inclusive.
ANSWER: { 7, 8, 9, 10}
[ 3x – 3 > 15, x > 6, hence {7, 8, 9, 10}
12. x is an integer less than 6.
ANSWER: { } the empty set or null set
[ 3x – 3 > 15, x > 6, but x < 6, hence the solution set is empty]
PREAMBLE: Provide the functions of the indicated proteins under one of the following:
Storage, Catalysis, Transport, Signal Transduction, Structure.
13. Haemoglobin
ANSWER: ANSWER: Transport
14. Collagen
ANSWER: Structure
15. Myoglobin
ANSWER: Storage
PREAMBLE: The specific heat capacity of water is .
16. What is the heat capacity of of water?
ANSWER:
17. How much water must be added to of water so that its heat capacity becomes ?
ANSWER:
so must be added.
18. How much water must be taken from of water so that its heat capacity becomes ?
ANSWER:
so must be
removed.
19. Calculate the moles of hydrogen gas that will be discharged in the electrolysis of concentrated NaCl
solution using inert electrodes after passing a charge of 0.3 Faraday.
ANSWER: Cathode: 2H+ + 2e → H2
Therefore, 2F ≡ 1 mol H2
Therefore, 0.3 F = (0.3 F/2F)*1 mol H2
Mole of H2 = 0.15 mol
20. Calculate the volume of oxygen discharged at STP at the anode of an electrolytic cell with inert
electrodes containing dilute CuSO4 solution after passing 0.7 Faraday of charge. Molar volume of a
gas at STP is 22.4 dm3.
Ans: At anode: H2O - 2e → 2 H+ + ½ O2
3
Therefore, 2F ≡ 22.4/2 dm of O2
Therefore, 0.7F = (0.7F/2F )* (22.4/2) dm3 of O2
Volume of O2 = 0.7 * 5.6 = 3.92 dm3
21. Calculate the mass of copper metal discharged at the cathode of an electrolytic cell with inert
electrodes containing dilute CuSO4 solution after passing 0.6 F of charge . Cu =
64.0
Ans: Cathode: Cu2+ + 2e → Cu
Therefore, 2F ≡ 64.0 g of Cu
0.6 F = (0.6 F/2 F) * 64 g Cu = 19.2 g Cu
PREAMBLE: Solve for n given that:
22. 32n + 2 = 81
ANSWER: n =1
[ 2n + 2 = 4, 2n = 2, n = 1]
23. 53n - 2 = 625
ANSWER: n = 2
[ 3n – 2 = 4, 3n = 6, n = 2]
2n – 3
24. 4 = 64
ANSWER: n = 3
[ 2n – 3 = 3, 2n = 6, n = 3]
ROUND 2 - SPEED ROUND
1. In a reaction of copper metal with HNO3 to give Cu(NO3)2, NO and H2O, how many moles of HNO3
react with 1 mole of Cu metal?
ANSWER: 4 moles.
[Cu + 4 HNO3 → Cu(NO3)2 + 2 NO + 2 H2O]
2. When sulphur is oxidized by concentrated H2SO4 to give H2O and SO2 gas what is the ratio of sulphur
to H2SO4 in a balanced equation?
ANSWER: S : H2SO4 ≡ 1 : 2
[S + 2H2SO4 → 3SO2 + 2H2O]
3. When cold water is dropped on solid aluminum sulphide, hydrogen sulphide gas and aluminium
hydroxide formed. How many moles of H2S can be obtained from a mole of aluminum sulphide?
ANSWER: 3 moles of H2S
[Al2S3 + 6 H2O → 2 Al(OH)3 + 3 H2S]
4. The nucleus of a cell contains a fixed number of chromosomes. Before mitosis, each chromosome
replicates to produce how many chromatids?
ANSWER: Two
5. What are the two main causes of heritable variation?
ANSWER: Mutations and recombination’s
6. What are the two primary sources of excessive nitrate and phosphate in rivers and lakes?
ANSWER: From sewage effluents and intensive agriculture.
7. Rank in order of increasing speed of yellow light: air, vacuum, glass, water.
ANSWER: Glass, water, air, vacuum
8. Convert to SI base units.
ANSWER:
9. What is the launch angle for maximum range of a projectile?
ANSWER:
10. Given that tanA = 1/3 and A is acute, evaluate tan 2A.
ANSWER: ¾ [tan2A = 2tanA/(1 – tan2A) = (2/3)/(1 – 1/9) = (2/3)/(8/9) = ¾]
11. Simplify (x + y)2 – (x – y)2
ANSWER: 4xy [(x + y – x + y)(x + y + x – y) = (2y)(2x) = 4xy
12. Find the next term in the sequence 1, 2, 4, 7, 11..
ANSWER: 16
PROBLEM OF THE DAY
Describe a simple experiment to demonstrate the presence of culturable
microorganisms in exhaled air.
SOLUTION
1. Prepare a sterile medium and pour into 2 Petri dishes.
2. below air from the mouth into the medium (at least 2 times)
3. cover the dish immediately and label the dish (eg A)
4. in the other sterile Petri dish do not blow air into it, which will serve as
control experiment and label it (eg B)
5. Place the tow Petri dishes in a warm cupboard or incubator and examine
them daily.
6. It will be observed that clusters of microorganisms (Colonies) will appear
on Petri dish A, and gradually increase in size.
7. There will be no growth of microorganisms in Petri dish B, which indicates
that the growth on Petri dish A, is from the exhaled air.
ROUND 4
TRUE OR FALSE
1. Vertically opposite angles are supplementary.
ANSWER: FALSE
2. Complementary angles are never congruent.
ANSWER: False
3. Any two right angles are congruent.
ANSWER: True
4. The symbol of the element antimony is Sb.
ANSWER: True
5. The symbol Ga stands for the element germanium.
ANSWER: False Ga = Gallium
6. The symbol for tungsten is Tg.
ANSWER: False Tungsten = W
7. The colour code for a resistor is red, red, red.
ANSWER: False
8. Black, red, red is the colour code for a resistor.
ANSWER: False
9. Black, black, red is the colour code for a resistor.
ANSWER: False
10. The mammalian pancreas is involved with the digestion of food only.
ANSWER: False
11. The mammalian pancreas is involved with the digestion and absorption of food.
ANSWER: False
12. The mammalian pancreas is involved with digestion of food, production of hormones and the
regulation of blood.
ANSWER: True
13. A parallelogram with congruent diagonals is a rectangle.
ANSWER: True
14. A rhombus with congruent diagonals is a square.
ANSWER: True
15. A trapezium is a parallelogram.
ANSWER: False
16. A solid in a test tube which on addition of concentrated H2SO4 produces a reddish brown vapour may
be an iodide.
ANSWER: False It is likely to be a bromide
17. A sodium halide whose neutral solution gives a cream precipitate with aqueous AgNO 3, is likely to be
a bromide.
ANSWER: True
18. A sodium halide whose solution gives a yellow precipitate with Pb2+ ions could be a chloride or a
bromide.
ANSWER: False Cannot be a chloride but can be a bromide. PbCl2 is white
19. The speed of a wave whose frequency is and wavelength is is .
ANSWER: True
20. The speed of a wave whose frequency is and wavelength is is .
ANSWER: False
21. The wavelength of a wave whose frequency is and whose speed is is .
ANSWER: True
PREAMBLE: State whether the following statements about the piliferous layer of roots are true or false.
22. It has a very thick cuticle.
ANSWER: False
23. It is the part of the root epidermis that bears root hairs.
ANSWER: True
24. It breaks down as the root ages.
ANSWER: True
ROUND 5
RIDDLES
RIDDLE 1
1. I am a type of mechanical disturbance.
2. That propagates through a material medium
3. I am characterized by compressions and rarefactions.
4. I am longitudinal, just like my cousin who is known to excite auditory response in humans.
5. I have no such effect on humans and I am ultra.
Who am I?
ANSWER: Ultrasound
RIDDLE 2
1. You can find up to three elements in my molecule.
2. I am an inorganic compound with covalent bonds when I am pure.
3. In solution I ionize easily and readily to give three ions.
4. I am manufactured more than any other chemical in the world.
5. My concentrated solution is a viscous liquid and a powerful dehydrating agent.
6. I am used in preparing an ammonium salt which is a well-known fertilizer.
Who am I?
ANSWER: (Concentrared)Sulphuric acid or tetraoxosulphate (IV) acid or H2SO4
RIDDLE 3
1. I am made from part of the neural tube during development.
2. I am located inside the vertebral canal.
3. In humans, I am divided into 31 different segments.
4. I am the main pathway for information connecting the brain and peripheral nervous system.
5. The brain and I together make up the central nervous system.
Who am I?
ANSWER: The spinal cord
RIDDLE 4
1. I am a three digit number.
2. I am an even number.
3. My first digit is the sum of the roots of the equation x2 – 3x + 5 = 0.
4. My second digit is the product of the roots of the same equation.
5. My last digit is the difference of my first two digits.
Who am I?
ANSWER: 352
