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JAMB Chemistry Past Questions 2015

10 questions from the JAMB 2015 Chemistry paper, with answers and explanations. Tap "Show answer" under each one when you are ready.

JAMB 2015Question 1 · Acids, Bases, and Salts
what is the pH of 0.00lmoldm 3 solution of sodium hydroxide
  1. A.14
  2. B.13
  3. C.12
  4. D.11
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Answer: D. 11

[]=0.001= mol/dm3, pOH=3, so pH=14-3=11.

JAMB 2015Question 2 · Atomic Structure and Chemical Bonding
Chlorine consisting of two isotope of mass number 35 and 37 in the ratio 3:1 has an atomic mass of 35.5. Calculate the relative abundance of the isotope of mass number 37
  1. A.20
  2. B.25
  3. C.60
  4. D.75
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Answer: B. 25

With a 3:1 ratio of mass-35 to mass-37 isotopes (4 parts total), the mass-37 isotope makes up = 25% relative abundance (check: 0.75x35+0.25x37=35.5).

JAMB 2015Question 3 · Chemistry of Non-metals and Gases
Atomicity of ozone is
  1. A.1
  2. B.2
  3. C.3
  4. D.4
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Answer: C. 3

Ozone is a triatomic molecule, so its atomicity is 3.

JAMB 2015Question 4 · Electrochemistry and Redox Reactions
The acid in electrolysis of water is dilute
  1. A.
  2. B.
  3. C.
  4. D.HCl
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Answer: C.

Dilute tetraoxosulphate(VI) acid is commonly used as the electrolyte in the electrolysis of water, to improve conductivity.

JAMB 2015Question 5 · Electrochemistry and Redox Reactions
In the electrolysis of brine the anode is
  1. A.platinum
  2. B.copper
  3. C.zinc
  4. D.carbon
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Answer: D. carbon

In the electrolysis of brine, an inert carbon (graphite) electrode is traditionally used as the anode.

JAMB 2015Question 6 · Environmental and Industrial Chemistry
Which of the following results in the fall of acid rain?
  1. A.oxide of lead
  2. B.particulate matter
  3. C.oxides of sulphur
  4. D.gaseous hydrocarbon
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Answer: C. oxides of sulphur

Oxides of sulphur (/) dissolve in atmospheric moisture to form sulphurous/sulphuric acid, causing acid rain.

JAMB 2015Question 7 · Organic Chemistry
Which of the following types of alkanols undergo oxidation to produce alkanoic acids. I. Primary alkanols II. Secondary alkanols III. Tertiary alkanols
  1. A.I, II and III
  2. B.I and II only
  3. C.III only
  4. D.I only
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Answer: D. I only

Only primary alkanols oxidize fully to alkanoic acids; secondary alkanols oxidize to alkanones (ketones), and tertiary alkanols resist oxidation.

JAMB 2015Question 8 · Periodicity and Inorganic Chemistry
Rare gases are stable because they
  1. A.are monoatomic
  2. B.form ions easily
  3. C.have duplet or octet electronic configuration in the outermost shells in their atoms
  4. D.are volatile gases
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Answer: C. have duplet or octet electronic configuration in the outermost shells in their atoms

Noble gases are stable because their atoms have complete duplet or octet electron configurations in their outermost shells.

JAMB 2015Question 9 · Physical Chemistry
When salt loses its water of crystallization to the atmosphere on exposure, the process is said to be
  1. A.efflorescence
  2. B.déliquescence
  3. C.effervescence
  4. D.fluorescence
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Answer: A. efflorescence

Loss of water of crystallization to the atmosphere is called efflorescence.

JAMB 2015Question 10 · Physical Chemistry
According to the kinetic theory an absence in temperature causes the kinetic energy of particles to
  1. A.decrease
  2. B.increase
  3. C.remain constant
  4. D.be zero
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Answer: A. decrease

By kinetic theory, a decrease in temperature reduces the average kinetic energy of particles.

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