CONTEST10

ROUND 1

State the functions of the following structures found in animal cells

1. Plasma membrane

ANSWER: Selective passage of molecules in and out of cells

2. Golgi apparatus

ANSWER: It processes, packages, and distributes molecules

3. Vacuoles

ANSWER: Storage of substances

4. How does the electrical conductivity of a metal vary when temperature is increased?

ANSWER: It decreases

5. How does the electrical conductivity of a semiconductor such as silicon vary when
temperature is increased?

ANSWER: It increases

6. How does the electrical conductivity of an insulator vary when temperature is increased?

ANSWER: It increases

7. Give the systematic name for a derivative of cyclobutane with the formula C6H12.

ANSWER: Ethylcyclobutane; cis or trans-1,2-dimethylcyclobutane, cis or

trans-1,3-dimethylcyclobutane

8. Name all the possible hexenes that be represented by the formula C6H12

ANSWER: 1- or 2- or 3-hexene//hex-1-ene etc

9. What is the difference in the chemical properties of an OH bonded to a saturated

carbon and an OH bonded to an aromatic carbon/nucleus?

ANSWER: OH bonded to a saturated carbon is neutral/an alkanol but one

bonded to an aromatic carbon is acidic/phenolic

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 10. Name the phase of meiosis where homologous chromosomes separate.

ANSWER: Anaphase I

11. Name the Phase of meiosis where bivalents are aligned at the equator of the spindle.

ANSWER: Metaphase I

12. Name the stage of meiosis where crossing over occurs.

ANSWER: Prophase I

13. Which of the following is not a vector quantity: energy, angular momentum, displacement,
and force?

ANSWER: Energy

14. Which of the following is not a scalar quantity: energy, angular momentum, distance, and
speed?

ANSWER: Angular momentum

15. Which of the following is not a signed quantity: speed, electric charge, atomic number, and
potential difference?

ANSWER: Atomic number and speed

Find the equation of the line passing through the given points

16. A(-2, 1) and B(-2 , 5)

ANSWER, x = -2 [x-coordinate same for both points]

17. C(-3, 5) and D(-10, 5)

ANSWER: y = 5 [y-coordinate same for both points]

18. E(-2, -2) and F(5, 5)

ANSWER: y = x [gradient m = 1, y + 2 = x + 2, and y = x]

19. When the concentration of a reactant A of a reaction is doubled, all others remaining
constant, the rate of the reaction increases by a factor of 8. What is the order of the
reaction with respect to reactant A?

ANSWER: 3rd order

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 20. When the concentration of a reactant B of a reaction is trebled, all others remaining
constant, the rate of the reaction increases by a factor of 9. What is the order of the
reaction with respect to reactant B?

ANSWER: 2nd order

21. When the concentration of a reactant C of a reaction is quadrupled, all others

remaining constant, the rate of the reaction does not change. What is the order of the
reaction with respect to reactant C?

ANSWER: Zero order

22. Which plant cell type are the most abundant of all cell types?

ANSWER: Parenchyma cells

23. What name is given to parenchyma cells with extensive connected air spaces?

ANSWER: Aerenchyma

24. Parenchyma cells containing numerous chloroplasts are collectively referred to as….

ANSWER: Chlorenchyma

25. What is the acceleration of a 5 kg mass acted on by a horizontal 2 N force directed to the left
and a horizontal 6 N force directed to the right?

ANSWER: to the right

Net force is to the right so acceleration is
.

26. What is the acceleration of a 2 kg mass attached by a horizontal inextensible string to a 5 kg

mass which is being pulled to the right by a horizontal 14 N force?

ANSWER: to the right

The two masses have the same acceleration
.

27. A 2 kg mass is attached by a horizontal inextensible string to a 5 kg mass which is being

pulled to the right by a 14 N horizontal force. What is the tension in the string?

ANSWER:
Acceleration of the 2 kg mass is and the force on it is
, which equals the tension in the string.

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If log5 = a and log 3 = b, find in terms of a and b

28. log 75

ANSWER: 2a + b [log75 = log25 + log3 = 2log5 + log3 = 2a + b]

29. log (9/125)

ANSWER: 2b – 3a [log9 – log125 = log32 – log53 = 2log3 – 3log5 = 2b – 3a ]

30. log(125/81)

ANSWER: 3a – 4b [log125 – log81 = log53 – log34 = 3log5 – 4log3 = 3a – 4b]

31. An element has a valence shell whose configuration is 4s23d6. What will be its
common valency or valencies?
ANSWER: Common valencies are +2 and +3

32. An element shows the following in its compounds: -1, +1, +2, +3, +4, +5, +6 and +7.
What is likely to be the electronic valencies configuration of its valence shell?

ANSWER: ns2np5

33. Why is the valency shell of chromium written as 4s13d5 and not 4s23d4?

ANSWER: In the former the sub-shells are both half-filled but not in the latter.
Half filled sub-shells are stable

34. What name is given to the pairs of chromosomes that associate together in prophase I
of meiosis?

ANSWER: Homologous chromosomes

35. What name is given to homologous chromosomes with sister chromatids joined by
nucleoprotein?

ANSWER: Bivalent/tetrad

36. The exchange of segments between non-sister chromatids of a bivalent during

meiosis is known as …………..

ANSWER: Crossing over

37. A body is acted upon by a 4 N force towards the east and a 3 N force towards the north.
What is the magnitude of the resultant force on the body?

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ANSWER:

38. A body of mass 5 kg is acted upon by a 10 N force towards the east and a 10 N force towards
the south. What is the magnitude of the acceleration the body?

ANSWER:

39. A2 N force towards the west and a 6 N force towards the east act on an object. What is the
work done when the object moves 2 m under the action of the forces?

ANSWER:

Differentiate the given function with respect to x

40. y = 5x4 – 6x2 – 10

ANSWER: dy/dx = 20x3 – 12x

41. y = 3x -3 + 5x2 -7x + 8

ANSWER: dy/dx = -9x-4 + 10x – 7

42. y = 5x3 – 6/x3

ANSWER: dy/dx = 15x2 + 18x-4

43. The electrode potentials of two half cells M+/M and Q+/Q (where M and Q are
metals), are -0.65 and -0.92volts, respectively. Calculate the initial emf of a cell that -
can be formed from the half cells. Indicate the anode of the cell.

ANSWER: Emf = oxidation potential + reduction potential (oxd pot = -red pot
of same ½ cell)

This sum must be positive for a spontaneous reaction

Hence Emf = +0.92 + -0.65 = 0.27 v

Anode (oxidation) hence Q metal

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44. Two half cells, X+/X and Y+/Y (where X and Y are metals) with electrode potentials
+0.45 and -0.76volts respectively are used to construct an electrochemical cell. What
will be the initial emf and which metal will be the cathode?

ANSWER: Emf = +0.76 + +0.45 = 1.21 v

Cathode (reduction) hence X metal

45. Two half cells, A+/A and B+/B (where A and B are metals) with electrode potentials
+0.32 and +0.80volts respectively are used to construct an electrochemical cell. What
will be the initial emf and in which direction will the current flow in the external
circuit?

ANSWER: Emf = -0.32 + +0.80 = 0.48 v

Current flows from oxidation/anode to the reduction/cathode

Hence, current flows from metal A to metal B in the external circuit.

Find the set of values of x for which

46. 4 + 5x > 20 – 11x

ANSWER: {x : x > 1} [4 + 5x > 20 – 11x, hence 16x > 16, and x > 1]

47. 17 – 5x < 9x + 45

ANSWER: {x : x > -2} [ 17 – 5x < 9x + 45, -14x < 28, 14x > - 28, x > - 2 ]

48. 9x – 17 + 6x – 8 > 20

ANSWER: {x : x < 3} [ 9x – 17 + 6x – 8 < 20, 15x < 45, x < 3]

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 PROBLEM OF THE DAY

The roots of the quadratic equation x 2  bx  c 0 are  and  .

a) Evaluate i)  2   2 , ii) (   )2
b) Find the quadratic equation whose roots are (  2   2 ) and (   )2

SOLUTION
a)     b ,  c (2 Marks)
i)  2   2 (   ) 2  2 b 2  2c (2 Marks)

ii) (   ) 2  2   2  2 b 2  2c  2c b 2  4c (2 Marks)

b) sum of roots = ( 2   2 )  (   ) 2 b 2  2c  b 2  4c 2b 2  6c (1 Mark)

product of roots = ( 2   2 )(   ) 2 (b 2  2c)(b 2  4c) (1 Mark)

Equation of the quadratic equation:
x 2  (2b 2  6c) x  (b 2  2c)(b 2  4c) 0 (2 Marks)
Total: 10 Marks

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ROUND 3 – True or False

1. Sin 2A = 2sinA
ANSWER: FALSE
2. Cos 2A = 1 – 2sin2A
ANSWER: TRUE
3. Cos(A – B) = cosAcosB + sinAsinB
ANSWER: TRUE
4. The curved surface area of a sphere is given by A = 4 r 2 where r is the radius.
ANSWER: TRUE
5. The volume of a pyramid is given by V = a half base area times height
ANSWER: FALSE [V = a third base area times height]
1
6. Area of a circle is A =  D 2 where D is the diameter
2
1
ANSWER: FALSE [A =  D2 ]
4
7. For a given amount of gas at a constant temperature a plot of V vs1/P will give a
straight line.

ANSWER: TRUE [PV = nRT for a given amount, R and T are constant]

8. A reaction is likely to be spontaneous if ΔHreaction is negative.

ANSWER: TRUE

9. In the Haber Process the catalyst does not alter the yield of ammonia.

ANSWER: TRUE [Catalysts hasten the attainment of equilibrium, they do not

change the equilibrium constant.]

10. Kerosene and aviation fuel are usually obtained from different fractions in the
distillation of crude oil.

ANSWER: FALSE

11. Reforming a distillate of crude oil involves transforming saturated hydrocarbons to

unsaturated hydrocarbons.

ANSWER: FALSE

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12. Branched chain hydrocarbons burn more smoothly than straight chain hydrocarbons
of the same molar mass.

ANSWER: TRUE

13. Lightning is an atmospheric electrical discharge event.

ANSWER: TRUE
14. Lightning can strike from ground to sky.
ANSWER: TRUE
15. Charge on a hollow conductor resides on the outside of the conductor.
ANSWER: TRUE
16. A Wheatstone bridge is used for comparing the masses of wires.
ANSWER: FALSE
17. A battery delivers maximum power when the load applied to it equals its internal resistance.
ANSWER: TRUE
18. A semiconductor becomes a perfect conductor at 0 K.
ANSWER: FALSE
19. The pigment in the eyes of insects absorbs shorter wavelengths of light than retina of
humans
ANSWER: TRUE
20. Bees are blind to ultraviolet light
ANSWER: FALSE (They can see)
21. Bees are blind to red light
ANSWER: TRUE
22. Vascular cambium and cork cambium are absent in monocotyledonous plants
ANSWER: TRUE
23. In dicotyledonous plants, vascular bundles of stem are scattered
ANSWER: FALSE
24. In monocotyledonous plants, flower parts occur in fours and multiples of four
ANSWER: FALSE

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ROUND 4 – Riddles
Riddle #1
1. You may refer to US as a twin organ, since we occur in pairs.
2. We are located on either side of the vertebral column, just below the diaphragm
where we enjoy partial protection by the lower rib cage.
3. We are shaped like beans and appear reddish brown in humans.
4. We are responsible for the production of urine in mammals.

WHO ARE WE?

ANSWER: KIDNEY

Riddle #2
1. I am a special geometric figure.
2. I am formed by two rays with a common endpoint.
3. That makes me an angle.
4. My measure is always greater than that of an acute angle but less than that of an
obtuse angle.
5. In a straight angle, there are two of me.
6. In the right type of triangle I am opposite the hypothenuse

WHO AM I?
ANSWER: A RIGHT ANGLE

Riddle #3
1. I am a binary compound.
2. I am very soluble in water.
3. I am normally gaseous at room temperature.
4. I am produced in an industrial process whose chemistry is often used to illustrate Le
Chaterlier’s Principle.
5. I or my aqueous solution turns red litmus blue.
6. My geometry is described as trigonal pyramid

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 WHO AM I?
ANSWER: AMMONIA/NH3

Riddle #4

1. I am a vector quantity.
2. I am derived from another vector quantity.
3. I am just the rate of change with time of that other vector.
4. .My magnitude can be constant while I am changing.
5. When that happens I describe uniform motion on a circle.
6. My magnitude is called speed.

WHO AM I?
ANSWER: VELOCITY

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