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Chemistry
UTME / JAMB 2019
Acids, Bases, and Salts
Solution
X is a substance which liberates CO\(_2\) on treatment with concentrated H\(_2\)SO\(_4\). A warm solution of X can decolorize acidified KMnO\(_4\). X is
A
HCOOH
B
NaHCO\(_3\)
C
FeCO\(_3\)
D
H\(_2\)C\(_2\)O\(_4\)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
It should be noted that for X to liberate CO\(_2\), X must be a carbonate or an oxalate. Since X decolorizes KMnO\(_4\), X must be an oxalate.
Therefore, X is H\(_2\)C\(_2\)O\(_4\).
Source: Myschool Past Questions Archive (Record #56011)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
The emission of two successive beta particles from the nucleus \(^{32} _{15} P\) will produce
A
\(^{30} _{14}\)Si
B
\(^{32} _{13}\)Al
C
\(^{32} _{17}\)Cl
D
\(^{32} _{16}\)S
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
\(^{32} _{15}\)P \(\to\) 2\(^{0} _{-1}\)e + \(^{a} _{b}\)X
32 = 2(0) + a
a = 32
15 = 2(-1) + b
b = 15 + 2
b = 17
\(\therefore\) \(^{a} _{b}\)X = \(^{32} _{17}\)Cl
Source: Myschool Past Questions Archive (Record #56013)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
Hydrogen diffused through a porous plug
A
thrice as fast as oxygen
B
at the same speed as oxygen
C
four times as fast as oxygen
D
twice as fast as oxygen
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Using Graham's Law of Diffusion,
\(\frac{R_1}{R_2} = \sqrt{\frac{m_2}{m_1}}\)
\(\frac{R_H}{R_O} = \sqrt{\frac{m_O}{m_H}}\)
\(\frac{R_H}{R_O} = \sqrt{\frac{32}{2}}\)
\(\frac{R_H}{R_O} = \sqrt{16} = 4\)
\(\therefore R_H = 4 \times R_O\)
Therefore, hydrogen diffuses 4 times faster than oxygen.
Source: Myschool Past Questions Archive (Record #56014)
Chemistry
UTME / JAMB 2019
Stoichiometry & Mole Concept
Solution
If the cost of electricity required to discharge 10g of an ion X\(^{3+}\) is N20.00, how much would it cost to discharge 6g of ion Y\(^{2+}\)?
[1 faraday = 96,500C, atomic masses are X = 27, Y = 24]
A
N10.00
B
N6.00
C
N20.00
D
N9.00
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
X\(^{3+}\) + 3e\(^-\) \(\to\) X
3F = 27g
xF = 10g
\(\frac{x}{3} = \frac{10}{27} \implies x = \frac{10}{9} F\)
\(\frac{10}{9}\)F \(\equiv\) N20.00
1F is equivalent to x
\(\frac{1}{\frac{10}{9}} = \frac{x}{20}\)
\(\frac{9}{10} = \frac{x}{20} \implies x = N18.00\)
1F is equivalent to N18.00.
Y\(^{2+}\) + 2e\(^-\) \(\to\) Y
2F = 24g
xF = 6g
x = \(\frac{6 \times 2}{24} = \frac{1}{2} F\)
1F = N18.00
\(\frac{1}{2}\)F = \(\frac{1}{2} \times N18.00\)
= N9.00
Source: Myschool Past Questions Archive (Record #56015)
Chemistry
UTME / JAMB 2019
Acids, Bases, and Salts
Solution
The cost of discharging 6.0g of a divalent metal, X from its salt is ₦12.00. What is the cost of discharging 9.0g of a trivalent metal, Y from its salt under the same condition?
[X = 63, Y = 27, 1F = 96,500C]
A
N12.00
B
N27.00
C
N63.00
D
N95.00
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
For X: X\(^{2+}\) + 2e\(^-\) \(\to\) X
2F = 63g
xF = 6g
x = \(\frac{6 \times 2}{63} = \frac{4}{21} F\)
\(\frac{4}{21}\)F = N12.00
1F = \(\frac{12}{\frac{4}{21}}\)
= N63.00
1F is equivalent to N63.00.
For Y: Y\(^{3+}\) + 3e\(^-\) \(\to\) Y
3F = 27g
xF = 9g
x = \(\frac{3 \times 9}{27}\)
= 1F
1F = N63.00
Source: Myschool Past Questions Archive (Record #56016)
Chemistry
UTME / JAMB 2019
Stoichiometry & Mole Concept
Solution
How many alkoxyalkanes can be obtained from the molecular formula C\(_4\)H\(_{10}\)O?
A
4
B
2
C
1
D
3
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
ethoxlethane
methoxylpropane
propoxylmethane
Source: Myschool Past Questions Archive (Record #56017)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
The reaction \(2H_2 S + SO_2 \to 3S + 2H_2 O\) is
A
not a redox reaction because there is no oxidant in the reaction
B
not a redox reaction because there is no reductant in the reaction
C
a redox reaction in which H\(_2\)S is the oxidant and SO\(_2\) is the reductant
D
a redox reaction in which SO\(_2\) is the oxidant and H\(_2\)S is the reductant
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 #56018)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
A solution X, on mixing with AgNO\(_3\) solution gives a white precipitate soluble in aqueous NH\(_3\), a solution Y, when also added to X, also gives a white precipitate which is soluble when heated solutions X and Y respectively contain
A
Al\(^{3+}\), Cl\(^-\)
B
Hg\(^+\), SO\(_4 ^{2-}\)
C
Pb\(^{2+}\), Cl\(^-\)
D
Ag\(^+\), SO\(_4 ^{2-}\)
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 #56019)
Chemistry
UTME / JAMB 2019
Atomic Structure and Periodic Table
Solution
How many electrons will be found in the nucleus of an atom with mass number 23 and 17 neutrons?
A
none
B
6
C
7
D
8
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Electrons are found in the orbit of the atom. They revolve around the nucleus. There's no electron found in the nucleus of an atom.
Source: Myschool Past Questions Archive (Record #56020)
Chemistry
UTME / JAMB 2019
Stoichiometry & Mole Concept
Solution
An element Z contains 80% of \(^{16} _8\)Z and 20% of \(^{18} _8\)Z. Its relative atomic mass is
A
16.2
B
17.6
C
16.0
D
16.4
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
R.A.M of Z = \(16(\frac{80}{100}) + 18(\frac{20}{100})\)
= \(12.8 + 3.6\)
= 16.4
Source: Myschool Past Questions Archive (Record #56021)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
When the end alkyl groups of ethyl ethanoate are interchanged, the compound formed is
A
propylmethanoate
B
ethylpropanoate
C
methyl ethanoate
D
methyl propanoate
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The structural formula for ethyl ethanoate is
After interchanging, we have
Which is the structural formula for methyl propanoate.
Source: Myschool Past Questions Archive (Record #56022)
Chemistry
UTME / JAMB 2019
Matter & Separation Techniques
Solution
The part of the total energy of a system that accounts for the useful work done in a system is known as
A
Enthalpy change
B
None of the above
C
Gibb's free energy
D
Entropy
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Gibb's free energy is the fraction of the total energy of a system that accounts for how much useful work can be done in a system.
Source: Myschool Past Questions Archive (Record #56023)
Chemistry
UTME / JAMB 2019
Kinetics, Energetics and Equilibrium
Solution
Which of the following factors will speed up the rate of evolution of carbon (iv) oxide in the reaction below?
2HCl + CaCO\(_3\) → CaCl\(_2\) + H\(_2\)O + CO\(_2\)
A
Increasing the concentration of the acid
B
Increasing the surface area of CaCO\(_3\)
C
A and B
D
Reducing the concentration of the acid
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The following factors increase a reaction rate
- Increase in concentration of reactants
- Increase in temperature
- Addition of catalyst
- Increase in the surface area of reactant(s)
Source: Myschool Past Questions Archive (Record #56024)
Chemistry
WAEC / WASSCE 2019
Matter & Separation Techniques
Solution
Which of the following metals reacts slowly with cold water?
A
Iron
B
Silver
C
Calcium
D
Pottassium
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Calcium reacts very slowly with cold water
Source: Myschool Past Questions Archive (Record #57916)
Chemistry
WAEC / WASSCE 2019
Acids, Bases, and Salts
Solution
The bleaching action of chlorine is through the process?
A
Hydration
B
Hydrolysis
C
Reduction
D
Oxidation
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The bleaching action lof chlorinr is due to its ability to react with water to form oxochlorate(i)acid
Source: Myschool Past Questions Archive (Record #57929)