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Chemistry
UTME / JAMB 1989
Periodic Table & Periodicity
The atomic radius of Li, Na and K are 1: 33A, 1. 54A and 1. 96A res pectively. Which of the following explaqins this gradation in atomic radius?
A
electropositivity decreases from Li to Na to K
B
electronegativity decreases from Li to Na to K
C
the number of the electron shells increases from Li to Na to K
D
the elements are in the same period
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 #27561)
Chemistry
UTME / JAMB 1989
Atomic Structure, Orbitals & Nuclear Chemistry
Solution
Elements X and Y have electronic configurations 1s\(^2\)2s\(^2\)2p\(^4\) and 1s\(^2\)2s\(^2\)2p\(^6\)3s\(^2\)3p\(^1\) respectively. When they combine, the formula of the compound formed is?
A
XY
B
YX
C
X2Y3
D
Y2X3
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
\(\frac{\text{Element X}}{1s^22s^21p^4}\)
Valency of X is 2
\(\frac{\text{Element Y}}{1s^22s^22p^63s^23P^1}\)
valency of Y is 3
There is an exchange of valency when a compound is being formed. Hence, we have Y\(_2\)X\(_3\)
Source: Myschool Past Questions Archive (Record #27562)
Chemistry
UTME / JAMB 1989
Atomic Structure, Orbitals & Nuclear Chemistry
The atomic number of caesium is 55 and its atomic mass is 133. The nucleus of caesium atom therefore contains
A
78 protons and 55 elections
B
55 protons and 78 neutrons
C
55 neutrons 78 electrons
D
78 protons and 55 neutrons
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 #27563)
Chemistry
UTME / JAMB 1989
Periodic Table & Periodicity
Four elements P,Q, R and S have atomic numbers of 4, 10, 12 and 14 respectively . Which of these electrons is a noble gas?
A
P
B
Q
C
R
D
S
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 #27564)
Chemistry
UTME / JAMB 1989
Atomic Structure, Orbitals & Nuclear Chemistry
Solution
How many valence electrons are contained in the element represented \(^{31}\) \(_{15}\)P?
A
3
B
5
C
15
D
31
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The element is Phosphorus in group 5 with valencies of 3 and 5.
The electronic configuration of phosphorus is 2,8,5. Hence it has two valencies of +5 and -3. Since we do have 3 and 5 in the options provided, the valency of 5 is a better option since it has positive while 3 has a negative value.
The electron configuration of phosphorus (atomic number 15) is 1s² 2s² 2p⁶ 3s² 3p³. Valence electrons are those in the outermost shell, which in phosphorus's case are the 3s² and 3p³ electrons, totaling 5.
Source: Myschool Past Questions Archive (Record #27565)
Chemistry
UTME / JAMB 1989
Metals, Transition Elements & Extraction
The gaseous pollutant sulphur (IV)oxide is most likely to be detected in fairly reasonable quantities in the area around a plant for the
A
extraction of aluminium from bauxite
B
production of margarine
C
smelting of copper
D
production of chlorine from brine
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 #27566)
Chemistry
UTME / JAMB 1989
Water, Solutions & Solubility
Solution
Calcium hydroxide is added in the treatment of town water supply to
A
kill bacteria in the water
B
facilitate coagulation of organic particles
C
facilitate sedimentation
D
improve the taste of the water
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Calcium hydroxide, also known as slaked lime, is added to water supply systems primarily to adjust the pH and provide hydroxide ions. This adjustment is crucial for optimizing the process of coagulation. When used alongside coagulants like alum (aluminum sulfate), it helps destabilize and clump together small suspended organic particles and impurities into larger masses called "flocs". These larger flocs are then much easier to remove during subsequent treatment stages like sedimentation and filtration.
Source: Myschool Past Questions Archive (Record #27567)
Chemistry
UTME / JAMB 1989
Nature of Matter & Separation Techniques
Solution
A hydrated salt of formula MSO4.xH2 O CONTAINS 45.3% by mass of water of crystalisation. Calculate the value of x [M = 56, S = 32, O = 16, H = 1 ]
A
3
B
5
C
7
D
10
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The formula is %age by mas of water of crystallization = [(Number of molecules of water x Molar mass of water) / Molar mass of hydrated salt] x100
i.e % by mass of water of crystallization = \(\frac{18x}{molar mass of MSO4.XH\(_2\)O} \times 100\)
Number of molecules of H\(_2\)O X Molar mass of H\(_2\)O = 18X
Molar mass of hydrated salt, MSO4.XH\(_2\)O = 56 + 32 + (16 X 4) + 18X = 152 + 18X
% by mass of H\(_2\)O of crystallization = 45.3%
% by mass of H\(_2\)O of crystallization = \(\frac{18x}{152 + 18x}\times 100\)
45.3% = \(\frac{18x}{152 + 18x}\times 100\)
\(\frac{45.3}{100}\) = \(\frac{18x}{152 + 18x}\)
100 x 18X = 45.3(152+18X)
1800X = 6885.6 + 815.4X
1800X - 815.4X = 6885.6
984.6X = 6885.6
X = \(\frac{6885.6}{984.6}\)
X = 6.993
X = 7.
Source: Myschool Past Questions Archive (Record #27568)
Chemistry
UTME / JAMB 1989
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Using 50 cm\(^3\) of 1 M potassium hydroxide and 100 cm\(^3\) of 1 M tetraoxosulphate (VI) acid, calculate the respective volumes in cm\(^3\) of base and acid that would be required to produce the maximum amount of potassium tetraoxosulphate (IV) [K = 39, S = 32, O = 16, H = 1]
A
50, 50
B
25, 50
C
50, 25
D
25, 25
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
First, let's write a balanced equation for the chemical reaction:
2KOH + H\(_2\)SO\(_4\) → K\(_2\)SO\(_4\) + 2H\(_2\)O
Reacting ratio: 2moles : 1 mole 1 mole
Reacting Volume: 50cm\(^3\) : 100cm\(^3\)
Actual volume that reacted: 50cm\(^3\) : 25cm\(^3\)
Residual : 0cm\(^3\) : 75cm\(^3\)
Volume of base (KOH) = 50 cm\(^3\)
Volume of acid (H\(_2\)SO\(_4\)) = 25 cm\(^3\)
Source: Myschool Past Questions Archive (Record #27569)
Chemistry
UTME / JAMB 1989
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
A solution of calcium bromide contains 20 g dm\(^3\). What is the molarity of the solution with respect to calcium bromide and bromide ions? [Ca = 40, Br = 80]
A
0. 1, 0 . 1
B
0. 1, 0. 2
C
0. 1, 0. 05
D
0.05, 0.1
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Given:
Concentration of CaBr\(_2\) = 20 gdm\(^{-3}\)
CaBr\(_2\) ⇌ Ca\(^{2+}\) + 2 Br\(^-\)
1mole 2moles
(a) Molarity (Molar concentration) of CaBr\(_2\) = \(\frac{Mass concentration}{Molar mass}\)
Molar mass of CaBr\(_2\) = 40 + (80 x 2) = 200g/mol
Molarity of CaBr\(_2\) = \(\frac{20}{200}\)
= 0.100M
(b) Since 1mole of CaBr\(_2\) produces 2moles of Br\(^-\)
Molarity of 2Br\(^-\) = 2 x 0.100
= 0.200M
The molarity of the solution with respect to calcium bromide and bromide ions are 0.10 and 0.20 respectively.
Source: Myschool Past Questions Archive (Record #27570)
Chemistry
UTME / JAMB 1989
Acids, Bases, pH & Salts
The substance ZnO dissolves in sodium hydroxide solution and mineral acid solution to give soluble products in each case. ZnO is therefore referred to as
A
an allotropic oxide
B
an amphoteric oxide
C
a peroxide
D
a dioxide
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 #27571)
Chemistry
UTME / JAMB 1989
Acids, Bases, pH & Salts
An acid and its conjugate base
A
can neutralise each other to form a salt
B
differ only by a proton
C
differ only by the opposite charges they carry
D
are always neutral substances
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 #27572)
Chemistry
UTME / JAMB 1989
Electrolysis & Electrochemical Cells
Solution
The same current is passed for the same time through solutions of AgNO3 and CuSO4 connected in series. How much silver will be deposited if 1.0 g of copper is produced?
[Cu = 63.5, S = 32, O = 16, Ag = 108, N = 14]
A
1.7 g
B
3.4 g
C
6. 8 g
D
13. 6 g
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
From Faraday;s second law of electrolysis
\(\frac{\text{Mass of silver deposited}}{\text{Mass of copper deposited}}\) = \(\frac{\text{Equivalent mass of silver}}{\text{Equivalent mass of copper}}\)
\(\frac{\text{Mass of silver deposited}}{1.0g}\) = \(\frac{108}{63.5}\)
= 31.75g
Copper is devalent = Cu2+
Mass of silver deposited = \(\frac{108g}{31.75g}\)
= 3.30g
Source: Myschool Past Questions Archive (Record #27573)
Chemistry
UTME / JAMB 1989
Electrolysis & Electrochemical Cells
Solution
What is discharged at the cathode during the electrolysis of copper (ll) tetraoxosulphate (VI) solution?
A
Cu 2+ only
B
H + only
C
Cu 2+ and H
D
Cu 2+ and SO 2-
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
During the electrolysis of copper(II) tetraoxosulfate (VI) solution (also known as copper sulfate solution), copper ions (Cu²⁺) are discharged at the cathode. This process results in the deposition of metallic copper on the cathode.
Source: Myschool Past Questions Archive (Record #27574)
Chemistry
UTME / JAMB 1989
Oxidation, Reduction & Redox Reactions
An element, Z froms an anion whose formula is [Z(CN)6]y. If Z has an oxidation number of +2, what is the value of y?
A
- 2
B
- 3
C
- 4
D
- 5
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 #27575)