ROUND 1

1. How many millimoles of NaOH are present in 250cm3 of 0.30 moldm-3 solution?
ANSWER: 75mmoles.
2. How many millimoles of NaOH are present in 8g of solid? (Na=23, O=16, H=1)
ANSWER: Moles of NaOH = 8/40 = 0.2
mmoles of NaOH = 20 mmoles.
3. How many mmole of H+ are present in 200cm3 of 0.15moldm-3solution of H2SO4.
ANSWER: mmole of H+ = 2(0.15*200) = 60.
= 60mmol.
. Preamble: Indicate the probable food substance in the following food tests.
4. Osmic acid was boiled with a sample of food substance and a black
precipitate appeared.
ANSWER: Fats and oil/lipid present

5. Millon’s reagent was boiled with a sample of food substance and a red
precipitate appeared
ANSWER: Protein present

6. A few drops of iodine solution was added to a sample of food substance a

blue-black colouration was formed
ANSWER: Starch
Preamble: An incompressible fluid with a density of 900 kg/m3 is located in a region
where the acceleration due to gravity is approximately 10 m/s2.

7. What is the gauge pressure at a depth of 20 m below the surface of the fluid?
ANSWER: 180 000 Pa
P = ρgh = 900 kg/m3 × 10 m/s2 × 20 m =180 000 Pa = 180 kPa
8. At what depth below the surface of the fluid is the gauge pressure 9000 Pa?
ANSWER: 1 m
9. What is the gauge pressure at a depth of 5 m below the surface of the fluid?
ANSWER: 45 kPa

1
Preamble: Find the remainder
10. f(x) = 3x2 – 7x + 6 divided by (x + 2)
ANSWER: R = 32 [f(-2) = 3(4) – 7(-2) + 6 = 32]
11. f(x) = 2x3 + 3x – 8 divided by (x - 1)
ANSWER: R = -3 [ f(1) = 2 + 3 – 8 = -3]
12. f(x) = 3x3 – 2x2 – 5 divided by (x - 2)
ANSWER: R = 11 [f(2) = 3(8) – 2(4) – 5 = 24 - 13 = 11]
13. In electrolysis what is the name given to the electrode connected to the negative pole
of the battery.
ANSWER: Cathode.
14. What reaction takes place at the cathode during electrolysis?
ANSWER: Cations or molecules are reduced.
15. What reaction takes place at the anode during electrolysis?
ANSWER: Oxidation or Anions migrate to the anode and discharge their
electrons.
16. What is the main function of the endosperm of seeds?
ANSWER. Storage of food
17. What is the pericarp?
ANSWER. The wall of a fruit
18. . Which parts of the flower forms the stalk of a fruit after fertilization?
ANSWER. Receptacle
19. Under what condition will a particle acted upon by two forces be in equilibrium?
ANSWER: When the forces have equal magnitude but opposite direction
20. What can be said about the net torque on an object in rotational equilibrium?
ANSWER: The net torque is zero
21. What is the state of equilibrium of a particle moving with constant velocity?
ANSWER: Dynamic equilibrium
x
22. If 3x – y = x + 3y, find the ratio
y
x 4
ANSWER: 2 [2 x=4 y , = =2]
y 2

2
 y
23. If 5x + 2y = 2x – y, find the ratio
x
y
ANSWER: -1 [3 x=−3 y , =− 1]
x
x
24. If 6x – 4y = x + 6y, find the ratio
y
x 10
ANSWER: 2 [5x = 10y, = =2 ]
y 5
25. What is wire gauze used for in the laboratory?
ANSWER: Normally placed on the tripod when heating a flask and its content
with a Bunsen burner;
(a) To prevent direct contact of the flame with the flask.
(b) To avoid overheating.
26. What is the main difference between a 25 cm3 pipette and a 25cm3 burette?
ANSWER: The burette has a tap and it is graduated. The pipette has no tap and
generally not graduated.
27. What is a test tube rack?
ANSWER: A piece of wood work or box with holes that allows the test tubes to
stand upright in them.
28. In which part of the heart is the bicuspid valve located?
ANSWER: Between the left auricle and the left ventricle.
29. Name the sheet of muscle that separates the thoracic cavity from the abdominal
cavity of mammals
ANSWER: Diaphragm
30. Name the component of the blood that has a high affinity for oxygen
ANSWER: Erythrocytes / Red blood cells
31. What is the acceleration of an object?
ANSWER: Rate of change of velocity
32. What is the acceleration of a uniformly moving object?
ANSWER: Zero
33. What is the effect of the component of acceleration perpendicular to the velocity of an object
on the motion of the object?
ANSWER: It changes the direction of motion
3
 Preamble: Express the given decimal number in the given base

34. 73 in base 8
ANSWER: 1118 [7 = 1(64) + 1(8) + 1 = 1118]
35. 57 in base 6
ANSWER: 1336 [57 = 1(36) + 3(6) +3(1) = 1336]
36. 87 in base 5
ANSWER: 3225 [87 = 3(25) + 2(5) +2(1) = 3225]

PROBLEM OF THE DAY

The mass of a particle is 9 ×10 −31 kg . It is moving at a speed of 20 m s −1. The speed of light in
vacuum is 3 ×10 8 m s −1.

a. How much energy will be released if all the mass of the particle were converted into

energy?

b. Determine the kinetic energy of the particle.

c. Determine the fraction of the rest mass energy that makes up its kinetic energy.

SOLUTION
2
a. E=m c2=9× 10−31 kg × ( 3× 108 m s− 1) =8.1 ×10− 14 J
1 1 −1 2
b. T = m v = × 9× 10 kg × ( 20 m s ) =1.8 × 10 J .
2 −31 −28
2 2

c. T / E=1.8× 10−28 J ÷ 8.1 ×10 −14 J =2.2 ×10− 15 .

4
 ROUND 3

TRUE OR FALSE

1. In sodium hydride the oxidation state of hydrogen is +1.

ANSWER: False it is -1.
2. Lithium hydride is expected to be partly covalent and partly ionic because of the
small size of Li+ ion.
ANSWER: False It is predominantly ionic because H- is not polarisable
3. Beryllium hydride is partly covalent and partly ionic.
ANSWER: True
4. Viruses neither feed nor respire.
ANSWER: True
5. Viruses have nucleus containing DNA
ANSWER: False
6. Viruses possess cell wall and cytoplasm
ANSWER: False
7. The mean can be estimated from a histogram.
ANSWER: False
8. The median can be estimated from a histogram.
ANSWER: True
9. The mode can be estimated from a histogram.
ANSWER: True

10. The interactions between the molecules of a solid are weaker than the interactions
between the molecules of a gas.
ANSWER: False
11. The interactions between the molecules of a liquid are stronger than the
interactions between the molecules of a gas.
ANSWER: True
12. The interactions between the molecules of a solid are stronger than the
interactions between the molecules of a liquid.
ANSWER: True

5
13. The hybridization of carbon in ethene is sp2.
ANSWER: True.
14. The hybridization of carbon of the carbonyl group is sp2.
ANSWER: True.
15. The hybridization of oxygen in methanol is sp2.
ANSWER: False sp3.
16. Producers contribute to the biomass of an ecosystem
ANSWER: True.
17. Consumers contribute to the biomass of an ecosystem
ANSWER: True.
18. Microorganisms contribute to the biomass of an ecosystem
ANSWER: True.
19. A relation can only be many to many or many to one.
ANSWER: False

20. A function can only be many to one or one to one.

ANSWER: True

21. A function that is many to one does not have an inverse

ANSWER: True [since it is not one-to-one]

22. The efficiency of a machine is the ratio of work input to work output.
ANSWER: False
23. The velocity ratio of a machine is the ratio of the distance moved by the load to
the distance moved by the effort.
ANSWER: False
24. The mechanical advantage of a machine is the ratio of load to effort.
ANSWER: True

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 ROUND 4

RIDDLES

RIDDLE # 1

1. I am a vector quantity.
2. I am a property of a moving object.
3. My rate of change tells the force on a moving object.
4. I am the product of mass and velocity.
Who am I?
ANSWER: Linear momentum

RIDDLE # 2

1. When I am dissolved in water, my heptatomic molecules disintegrate into three units

2. Two of the units are friends of Arrhenius
3. My molecules are derived from three different elements
4. Without me transportation in Accra would completely come to a halt
Who am I?
ANSWER: H2SO4

RIDDLE 3

1. I am an odd 4 digit number.

2. All my digits are identical and each is a square.
3. I am the last of my kind.
4. The difference of any two of my digits is zero.
Who am I?
ANSWER: 9999

7
RIDDLE # 4

1. I am a catabolic process
2. My process is completely absent in plants
3. I am often divided into two processes, mechanical and chemical.
4. I am the main process by which food is broken down into simple absorbable form
WHO AM I?
ANSWER: Digestion