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Physics
UTME / JAMB 2021
Magnetism, Electromagnetism & AC Circuits
Solution
A 2H inductor has negligible resistance and is connected to a \(\frac{50}{\pi}\) Hz A.C supply. The reactance of the inductor is?
A
200\(\Omega\)
B
50\(\Omega\)
C
\(\frac{100}{\pi}\)
D
\(\frac{25}{\pi \Omega}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Given;
L = 2H
F = \(\frac{50}{\pi}\) \(H_2\)
\(X_L\) = ?
\(X_L\) = 2\(\pi\)fL = 2\(\pi\) x \(\frac{50}{\lambda}\) x 2
= 200\(\Omega\)
Source: Official Exam / Past Question Archive
Physics
WAEC / WASSCE 2021
Current Electricity & Electric Circuits
Solution
(a) You are provided with a battery, an ammeter, a voltmeter, a resistance box, a key and connection wires.
(i) Set up circuit as shown in the diagram above.
(ii) With the key opened, measure and record the e.m.f. E\(_o\) of the battery
(iii) With the key closed, select the resistance R=1 on the resistance box. Read and record the current, 1Ω.
(iv) Evaluate I\(^{-1}\).
(v) Repeat the procedure for five other values of R=2Ω,3Ω, 4Ω, 5Ω, and 6Ω.
In each case, record I and evaluate I\(^{-1}\) results.
(vii) Plot a graph with R on the vertical axis and I\(^{-1}\) on the horizontal axis.
(Viii) Determine the slope, s, of the graph.
(ix) Determine the intercept C, On the vertical axis.
(x) State two precautions taken to ensure accurate results.
(b)(i) Define potential difference in an electric field.
(ii) A piece of resistance wire of diameter 0.2 mm and length 25 cm has a resistance of 7Ω. Calculate the resistivity of the wire of the battery. [ \pi = 22\7]
A
Isaac Newton
B
Ernest Rutherford
C
Louis de Broglie
D
J.J. Thompson
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
SEE GRAPH ABOVE
(vii) Slope = \(\frac{\Deltad}{\DeltaI^{-1}}\) = \(\frac{d_2 - d_1}{I_2 - I^{-1}\)
→ \(\frac{80 - 30}{3.333 - 15}\} = \(\frac{50}{1.833}\)
Slope = 27.2cm / A
Precaution:
We should avoid parallax error by placing both eyes at the measured level.
We should always switch the fan off to ensure no external environment interferes with the result.
Diameter d = 0.6cm = 0.006m
: r = \(\frac{0.006}{2}\) = 0.003m
Resistivity = 1.0 x 10\(^{-6}\)
R = 4Ω
R = \(\frac{ρL}{A}|) → L = \(\frac{RA}{ρ}\)
L = \(\frac{ 4 x 22 x 0.0000009}{7 x 1.0 x 10^{-6}}\)
L = 6.289 x 2 x 9 x 10\(^{-6}\) x 10\(^{-6}\)
L = 113.14 x 10\(^{-6 + 6}\)
L = 113.14
Source: Official Exam / Past Question Archive
Chemistry
UTME / JAMB 2021
Particulate Nature of Matter, Laws & Formulae
Solution
The scientist who stated that matter can be converted into energy is?
A
Boyle
B
Lavoiser
C
Avogadro
D
Einstein
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The principle described by the physicist Albert Einstein's famous formula: E = mc^2, involves mass–energy equivalence.
I.e. the relationship between mass and energy.
Source: Myschool Past Questions Archive (Record #60412)
Chemistry
UTME / JAMB 2021
Oxidation, Reduction & Redox Reactions
Solution
A 'breath test' used by traffic police to check drunken driving uses?
A
Tumeric on filter paper
B
Silica gel coated with saliva nitrate
C
Potassium permanganate-sulphuric acid
D
Potassium dichromatic-sulphuric acid
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The earliest developed breathalyzer was based on reaction of alcohol if present in the exhaled air with a cocktail of chemicals containing sulfuric acid, potassium dichromate, silver nitrate, and water. Silver nitrate catalyzes the reaction between alcohol and potassium dichromate in acidic medium.
Source: Myschool Past Questions Archive (Record #60422)
Chemistry
UTME / JAMB 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following are chemical changes?
I. cooking of food
II. digestion of food
III. freezing of water
IV. water is heated up
A
I and II
B
I, II, and III
C
III and IV
D
all of the above
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #60462)
Chemistry
UTME / JAMB 2021
Atomic Structure, Orbitals & Nuclear Chemistry
Solution
Neutrons were discovered by?
A
James Chadwick
B
Ernest Rutherford
C
J.J Thompson
D
John Dalton
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
- Sir James Chadwick, was a British physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932.
- Ernest Rutherford postulated the nuclear structure of the atom, discovered alpha and beta rays, and proposed the laws of radioactive decay.
- Sir Joseph John Thomson was a British physicist and Nobel Laureate in Physics, credited with the discovery of the electron, the first subatomic particle to be discovered.
- John Dalton was an English chemist, physicist and meteorologist. He is best known for introducing the atomic theory into chemistry
Source: Myschool Past Questions Archive (Record #60470)
Chemistry
UTME / JAMB 2021
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
The inherited traits of an organism are controlled by?
A
RNA molecules
B
Nucleotides
C
DNA molecules
D
Enzymes
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
DNA now has three distinct functions—genetics, immunological, and structural—that are widely disparate and variously dependent on the sugar phosphate backbone and the bases.
Source: Myschool Past Questions Archive (Record #60502)
Chemistry
UTME / JAMB 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
The heat required to raise the temperature of the body by 1k is called?
A
Specific heat
B
Thermal capacity
C
Water equivalent
D
None of the above
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Heat capacity or thermal capacity: The amount of heat to be supplied to an object to produce a unit change in its temperature(1k).
Source: Myschool Past Questions Archive (Record #60506)
Chemistry
WAEC / WASSCE 2021
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
The hydrolysis of proteins by diluting mineral acids produces
A
sucrose
B
glucose
C
amino acids
D
fatty acids
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #61871)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
The ratio of carbon atoms of hydrogen atoms in a hydrocarbon is 1:2. If its molecular mass is 56, what is its molecular formula?
A
\(C_3\)\(H_6\)
B
\(C_4\)\(H_8\)
C
\(C_2\)\(H_4\)
D
C\(H_2\)
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #61879)
Chemistry
WAEC / WASSCE 2021
Particulate Nature of Matter, Laws & Formulae
Solution
What is the relative molecular mass of the compound below?
[H = 1.0; C = 12.0; O = 16.0]
A
137
B
136
C
64
D
59
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The molecular formula of the compound in question is \(C_6H_5COOCH_3\)
Then its relative molecular mass = 8C + 8H + 2O = 8 X 12 + 8 x 1 + 2 X 16 = 136
Source: Myschool Past Questions Archive (Record #61883)
Chemistry
WAEC / WASSCE 2021
Electrolysis & Electrochemical Cells
Cathodic protection of metals is based on
A
standard electrode potential of hydrogen
B
its electrical conductivity
C
nature of oxides formed
D
relative tendencies of oxidation
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #61887)
Chemistry
WAEC / WASSCE 2021
Oxidation, Reduction & Redox Reactions
Solution
If humid air is polluted by chlorine discharged, the air can be restored by sprinkling
A
solid Mn\(O_2\)
B
acidified KMn\(O_4\)
C
acidified FeS\(O_4\)
D
saturated NaCl(aq)
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Chlorine is a toxic gas and when it pollutes the air, it can be neutralized by using acidified KMnO4. The reaction between chlorine and acidified KMnO4 results in the formation of chloride ions, manganese(II) ions, and water, which are harmless. This is why acidified KMnO4 is used to restore air polluted by chlorine discharge.
Source: Myschool Past Questions Archive (Record #61888)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?
A
NaCl and KN\(O_3\)
B
KCL and NaN\(O_3\)
C
\(K_2\)S\(O_4\) and BaC\(l_2\)
D
N\(H_4\)N\(O_3\) and C\(O_3\)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
when potassium sulfate is mixed with barium chloride a white precipitate of barium sulfate will be form. barium sulfate is slightly soluble in water, so it will precipitate out as a solid
BaCl2 + K2SO4 → BaSO4 + 2KCl
note; all substances are aqueous except BaSO4 which is solid
Source: Myschool Past Questions Archive (Record #61891)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following illustrates the variation of the rate of evolution of gas from a given length of magnesium ribbon (y-axis) with an increase in the concentration of the added (x-axis)?
A
I
B
II
C
III
D
IV
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #61893)