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Physics
UTME / JAMB 2009
Lenses & Optical Instruments
Solution
The ability of the human eye to focus object on the retina is referred to as the power of?
A
interference
B
diffraction
C
accomodation
D
superposition
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Accommodation is the adjustment of the optics of the eye to keep an object in focus on the retina as its distance from the eye varies.
Source: WAEC / JAMB / NECO Classroom Archive (Record #14244)
Chemistry
UTME / JAMB 2009
Nature of Matter & Separation Techniques
Solution
A mixture of sugar and sulphur can be separated by?
A
dissolution in water, evapouration and filtration
B
filtration, evaporation and dissolution in water
C
dissolution in water, filtration and evaporation
D
evaporation, dissolution in water and filtration
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Sulfur is insoluble in water but sugar is soluble.
Hence; dissolution of sugar to have sulfur as the only insoluble solid.
Filtration: The filtrate is the liquid that passes through the filtration filter. Meanwhile, the residue is the solid that remains on the filtration filter.
Evaporation: water as part of the filtrate changes into a gas to leave sugar as residue.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4283)
Chemistry
UTME / JAMB 2009
Nature of Matter & Separation Techniques
Solution
Which of the following is a physical change?
A
Freezing ice cream
B
dissolving calcium in water
C
burning kerosene
D
Exposing white phosphorus to air
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Freezing is a physical change. It involves a liquid changing states to a solid. Thus, freezing a substance will not change its chemical identity, but its state.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4286)
Chemistry
UTME / JAMB 2009
Nature of Matter & Separation Techniques
Solution
The percentage of water of crystallization in ZnSO\(_4\).7H\(_2\)O is?
[Zn = 65, S = 32, O = 16, H = 1]
A
33%
B
44%
C
55%
D
87%
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
molar mass of water [7H\(_2\)O] = 7[ 2 * 1 + 16] → 7 * 18 = 126g/mol
molar mass of ZnSO\(_4\).7H\(_2\)O = [65 * 1] + [32 * 1] + [16 * 4] + 7[ 2 * 1 + 16]
→ 65 + 32 + 64 + 126 = 287g/mol
percentage of water of crystallization = \(\frac{mass of water of crystallization}{mass of hydrated compound} * 100%\)
→ \(\frac{126}{287} * 100\) = 43.9
≈ 44%
Source: WAEC / JAMB / NECO Classroom Archive (Record #4287)
Chemistry
UTME / JAMB 2009
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
0.0075 mole of calcium trioxocarbonate (IV) is added to 0.015 mole of a solution of hydrochloric acid. The volume of gas evolved at s.t.p is?
[Molar volume of a gas at s.t.p = 22.4 dm3]
A
224cm3
B
168cm3
C
112cm3
D
100cm3
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
1mole of gas at STP = 22.4dm\(^3\)
0.0075 mole of CaCO3 = xdm\(^3\)
cross multiply;
where 22.4dm\(^3\) = 22400cm\(^3\)
x * 1 = 0.0075 * 22400 → 168cm\(^3\)
the gas CO2 which evolved was gotten from CaCO3 so we use the number of moles of CaCO3 only
Source: WAEC / JAMB / NECO Classroom Archive (Record #4291)
Chemistry
UTME / JAMB 2009
Periodic Table & Periodicity
Solution
If an atom is represented as \( _{11}^{23}X \), which of the following deduction is correct?
A
it contains 12 protons
B
it forms a covalent chloride
C
its atomic number is 23
D
it is an alkali metal
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Sodium has atomic / proton number of 11 and belongs to Group 1[alkali metals] on the periodic table
Source: WAEC / JAMB / NECO Classroom Archive (Record #4296)
Chemistry
UTME / JAMB 2009
Atomic Structure, Orbitals & Nuclear Chemistry
Solution
Which quantum number divides shells into orbitals?
A
principal
B
Arzimuthal
C
Magnetic
D
Spin
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The principal quantum number, n, describes the energy of an electron and the most probable distance of the electron from the nucleus.
In other words, it refers to the size of the orbital and the energy level an electron is placed in.
The azimuthal quantum number is a quantum number for an atomic orbital that determines its orbital angular momentum and describes the shape of the orbital.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4299)
Chemistry
UTME / JAMB 2009
Chemical Bonding & Intermolecular Forces
Solution
The type of bonding in \({Cu(NH_3)_4}^2\)+ is?
A
coordinate covalent
B
electrovalent
C
metallic
D
covalent
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
\({Cu(NH_3)_4}^2\)+: The bonding in this ion consists of coordinate covalent bonds with all bonding electrons supplied by the nitrogen atom.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4300)
Chemistry
UTME / JAMB 2009
Oxidation, Reduction & Redox Reactions
Solution
The oxidation state of Cr in K\(_2\)Cr\(_2\)O\(_7\) is?
A
+7
B
+6
C
+5
D
4
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Potassium dichromate, K\(_2\)Cr\(_2\)O\(_7\)
→ [1 * 2] + [Cr * 2] + [-2 * 7] = 0
→ 2 + 2Cr - 14 = 0
→ 2Cr = 12
→Cr = \(\frac{12}{2}\) → 6
Source: WAEC / JAMB / NECO Classroom Archive (Record #4317)
Chemistry
UTME / JAMB 2009
Kinetic Theory of Matter & Gas Laws
Solution
A gas exerts pressure on its container because?
A
the molecules of a gas collide with the walls of the container
B
some of the molecules are moving faster than others
C
of the collisions of the molecules with each other
D
of the mass of the molecules of the gas
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Gas pressure is the name given to the force exerted by gas particles colliding with the wall of their container.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4293)
Chemistry
UTME / JAMB 2009
Kinetic Theory of Matter & Gas Laws
Solution
The basic assumption in the kinetic theory of gases that the collisions of the gaseous molecules are perfectly elastic implies that the?
A
forces of attraction and repulsion are in equilibrium
B
gaseous molecules can occupy any available space
C
gaseous molecules will continue their motion indefinitely
D
gases can be compressed
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies remains the same.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4294)
Chemistry
UTME / JAMB 2009
Acids, Bases, pH & Salts
Solution
The salt formed from a reaction between citric acid and sodium hydroxide in solution will be?
A
acidic
B
basic
C
complex
D
neutral
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Citric acid has 3 carboxyl groups, therefore, when reacts with NaOH, there is a simple salification reaction that will produce the trisodium citrate / sodium citrate.
Trisodium citrate is a tribasic salt of citric acid. It is produced by complete neutralization of citric acid with high purity sodium hydroxide or carbonate and subsequent crystallization and dehydration.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4314)
Chemistry
UTME / JAMB 2009
Air & Environmental Chemistry
Solution
The mixture of gases used in a photographer's flash tube is?
A
argon and krypton
B
krypton and xenon
C
helium and argon
D
argon and xenon
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
krypton and xenon for high-speed pictures in a photographer's flash tube
Source: WAEC / JAMB / NECO Classroom Archive (Record #4301)
Chemistry
UTME / JAMB 2009
Air & Environmental Chemistry
Solution
When sodium trioxocarbonate (IV) decahydrate loses its water of crystallization to the atmosphere, the process is?
A
deliquescence
B
efflorescence
C
hygroscopic
D
effervesecence
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
efflorescence, spontaneous loss of water by a hydrated salt, e.g Sodium trioxocarbonate (IV) decahydrate \(Na_2CO_3. 10H_2O)\) also known as washing soda
Source: WAEC / JAMB / NECO Classroom Archive (Record #4303)
Chemistry
UTME / JAMB 2009
Electrolysis & Electrochemical Cells
Solution
The acid used in electrolysis of water is dilute?
A
HNO3
B
CH3COOH
C
H2SO4
D
HCl
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The electrolyte is dilute sulfuric acid (= acidified water) which, during electrolysis is split into hydrogen and oxygen gases.
Source: WAEC / JAMB / NECO Classroom Archive (Record #4311)