JAMB Chemistry Previous Year Questions: 2021 | Chemistry for JAMB PDF Download

Q1: What is the common name for the following compound (CH₃)₂ CH CH₂ -Br
(a) Isobutyl bromide
(b) Methyl bromide
(c) propyl bromide
(d) Butyl bromide
Ans: (a)
The common name: Isobutyl bromide
The IUPAC name: 1-Bromo-2-methylpropane
Formula: C₄H₉Br

Q2: The enzyme that converts glucose to ethyl alcohol is?
(a) maltase
(b) zymase
(c) Diatase
(d) Invertase
Ans: (b)
Zymase is an enzyme complex that catalyzes the fermentation of sugar into ethanol and carbon dioxide. It occurs naturally in yeasts.

Q3: The scientist who stated that matter can be converted into energy is?
(a) Boyle
(b) Lavoiser
(c) Avogadro
(d) Einstein
Ans: (d)
Albert Einstein's theory of special relativity defines the relationship between mass and energy, E = mc² 

Q4: What is the IUPAC name for the following compound? HC ≡ CCH₃ 
(a) Acetylene
(b) Methylacetylene
(c) Butanol
(d) Decanoic acid
Ans: (b)
Propyne (methylacetylene), an alkyne with the chemical formula HC ≡ CCH₃ 

Q5: What is the chemical name for the compound CuCO₃?
(a) Copper (iii) carbonate
(b) Copper (ii) carbonate
(c) Copper (i) carbonate
(d) Copper
Ans: (b)
Copper(II) carbonate or cupric carbonate. Chemical compound formula CuCO₃ 

Q6: 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
Ans: (d)
A breathalyzer or breathalyser is a device used for estimating blood alcohol content (BAC), or to detect viruses or diseases from a breath sample.

Q7: Which one of the following is not a mixture?
(a) Air
(b) Mercury
(c) Milk
(d) Cement
Ans: (b)
A  mixture is a material made up of two or more different chemical substances which are not chemically combined.
Mercury with the chemical symbol Hg and the atomic number 80 is an element that has not reacted with another substance. When mercury reacts with another substance, it forms a compound, such as inorganic mercury salts.

Q8: Which of the following is a non-metal that remains liquid at room temperature?
(a) Chlorine
(b) Phosphorus
(c) Bromine
(d) Helium
Ans: (c)
Bromine, with the symbol Br and atomic number 35, is the third-lightest halogen. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour.

Q9: 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
Ans: (a)

Q10: The atomic weight of nitrogen is?
(a) 10
(b) 12
(c) 14
(d) 16
Ans: (c)
Atomic weight or Relative Atomic Mass is the ratio of the average mass of a chemical element's atoms to some standard, defined as the weighted average of the masses of the isotopes of an element compared to 1/12 of the mass of the carbon-12 atom. The formula for relative atomic mass is ?isotope mass x isotope abundance / 100.

Q11: Which gas causes global warming?
(a) O₂
(b) CO₂
(c) N₂
(d) He
Ans: (b)
Carbon dioxide (CO₂) is the primary greenhouse gas emitted through human activities
CO₂ is a colourless gas having a faint sharp odour and a sour taste.
Global warming is the long-term heating of the Earth's surface observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere.

Q12: Oxygen is absent in?
(a) Kerosene
(b) Soil
(c) Glass
(d) Cement
Ans: (a)
There is no oxygen in the Kerosene. Kerosene gets oxygen from the air.

Q13: A sample of any of the following substances disappears after some time when exposed to air like camphor, naphthalene, or dry ice. This phenomenon is called?
(a) Sublimation
(b) Evaporation
(c) Diffusion
(d) Radiation
Ans: (a)
Sublimation is the transition of a substance directly from the solid phase to the gas phase without passing through the intermediate liquid phase.
Substances that sublime readily include iodine, dry ice, menthol, and camphor.

Q14: The maximum electron in N shell is?
(a) 2
(b) 8
(c) 18
(d) 32
Ans: (d)
The N shell is the fourth orbit with 32 maximum number of electrons using 2n²

Q15: Neutrons were discovered by?
(a) James Chadwick
(b) Ernest Rutherford
(c) J.J Thompson
(d) John Dalton
Ans: (a)
James Chadwick, a British physicist, in May 1932.

Q16: Which of the following is a form of calcium carbonate?
I. limestone
II. marble
III. chalk
Iv. egg-shells
(a) I only
(b) I, II and IV
(c) I and II only
(d) I, II, III, and IV
Ans: (d)
Calcium trioxocarbonate (IV) occurs abundantly in the earth's crust as limestone, chalk and marble. Eggshell is mainly made up of calcium carbonate (CaCO₃) crystals.

Q17: Soaps clean surfaces on the principle based on?
(a) viscosity
(b) floatation
(c) elasticity
(d) surface tension
Ans: (d)
The surface tension forces become smaller as the distance between water molecules increases, the intervening soap molecules decrease the surface tension.

Q18: The reactivity of fluorine is due to what?
(a) its high electro negativity
(b) small size of fluorine atom
(c) availability of D-orbitals
(d) strong f-f bond
Ans: (a)
Fluorine (F) is the most reactive chemical element and the lightest member of the halogen elements.
The great reactivity of fluorine largely stems from the relatively low dissociation energy, a standard measure for bond energies, of the F?F bond (37.7 kilocalories per mole) and its ability to form stable strong bonds with essentially all the other elements.

Q19: The mass number of a nucleus is?
(a) Always less than its atomic number
(b) The sum of the number of protons and neutrons present in the nucleus
(c) Always more than the atomic weight
(d) A fraction
Ans: (b)
The mass number is the sum of the number of protons and neutrons present in the nucleus of an atom.

Q20: The mass of one Avogadro number of helium atoms is?
(a) 1.00gram
(b) 4.00gram
(c) 8.00gram
(d) 6.00gram
Ans: (b)
Avogadro's number is an absolute number: there are 6.022 × 10²3 elementary entities in 1 mole.
Helium has a molar mass of 4.0 grams per mole. So one mole of Helium has a mass of 4.0 grams.

Q21: 220g of carbon dioxide contains ----- moles
(a) 5
(b) 6
(c) 3
(d) 4
Ans: (a)
One mole of carbon dioxide molecules has a mass 44.01g.
220/44.01 = 4.9989
Hence, 5 mole of carbon dioxide molecules.

Q22: The inherited traits of an organism are controlled by?
(a) RNA molecules
(b) Nucleotides
(c) DNA molecules
(d) Enzymes
Ans: (c)
DNA is the hereditary material in humans and almost all other organisms. DNA codes genetic information for the transmission of inherited traits.

Q23: The most abundant rare gas in the atmosphere is?
(a) He
(b) Ne
(c) Ar
(d) Xe
Ans: (c)
Nitrogen (N₂) is the most abundant naturally occurring gas is Nitrogen (N₂), making up about 78% of air.
Oxygen (O₂), on the other hand, is the second most abundant gas making up about 21%.

Q24: 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
Ans: (b)
Heat capacity, also known as thermal capacity, is a physical property of matter defined as the amount of heat needed to cause a unit change in temperature in a given mass of material.

Q25: The nucleus of a hydrogen atom consists of a?
(a) 1 proton only
(b) 1 proton, 2 neutron
(c) 1 neutron only
(d) 1 electron only
Ans: (a)
The hydrogen atom is the simplest of all atoms, consisting of a single proton and a single electron.

Q26: The metal used to recover copper from a solution of copper sulphate is?
(a) Na
(b) Ag
(c) Hg
(d) Fe
Ans: (d)
The ideal metals are metals that are stronger reducing agents than copper but not reactive enough to react with the water that the solution consists of.
Examples of such metals:

• Zinc
• Aluminium
• Iron

Q27: The nucleus of an atom consists of?
(a) Electrons and neutrons
(b) Electrons and protons
(c) Protons and neutrons
(d) None of the above
Ans: (c)
The nucleus of an atom consists of protons and neutrons.
The electron is a negatively charged subatomic particle that orbits the nucleus of an atom.

Q28: A solution contains 20g of solute in 180g of solvent. If the solvent is water, what is the concentration of the solution in terms of mass by mass percentage?
(a) 11.%
(b) 22.2%
(c) 10%
(d) 20%
Ans: (c)
Mass of solution = Mass of solute + Mass of solvent ? 20g + 180g
Hence, Mass of solution = 200g


Q29: The only metal that is anti-bacterial is?
(a) Iron
(b) Sodium
(c) Aluminium
(d) Copper
Ans: (d)
Copper is antibacterial

Q30: An element having the atomic number 17 will resemble which of the following elements having an atomic number as given below?
(a) 33
(b) 35
(c) 18
(d) 19
Ans: (b)
The Group 7 elements are called "halogens". They appear in the vertical column, second from the right, in the periodic table.
Bromine(35) is among the elements in the Group.

Q31: A chemical process in which there is a gain of electrons is known as___?
(a) Sublimation
(b) Reduction
(c) Oxidation
(d) Distillation
Ans: (b)
Redox is a type of chemical reaction in which the oxidation states of the substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, likewise, reduction is the gain of electrons or a decrease in the oxidation state.

Q32: The reactions involving simultaneous oxidation and reduction?
(a) Automatic reactions
(b) Alternate reactions
(c) Reduction agency
(d) Redox reactions
Ans: (d)
Redox is a type of chemical reaction in which the oxidation states of the substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, likewise, reduction is the gain of electrons or a decrease in the oxidation state.

Q33: A binary compound of oxygen with another element is referred to as?
(a) Oxide
(b) Element
(c) Carbon
(d) Nitrogen
Ans: (a)
An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula.

Q34: The process or act of extracting a metal from its ore and refining it is called?
(a) Extraction
(b) Metal mining
(c) Mettallurgy
(d) Prospecting
Ans: (c)
Metallurgy is the art and science of extracting metals from their ores and modifying the metals for use. It is also defined as a domain of materials science and engineering that studies the physical and chemical behaviour of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.

Q35: The compounds made up of only carbon and hydrogen are called?
(a) Carbon compounds
(b) Hydrocarbons
(c) Atoms
(d) Carbon hydrolysis
Ans: (b)
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odours are usually weak or exemplified by the odours of gasoline and lighter fluid.
Natural sources of hydrocarbon are coal, natural gas and petroleum.

Q36: Which of the following is not a physical property of monosaccharides?
(a) Monosaccharides get charred when heated
(b) Monosaccharides are water-soluble, sweet substances
(c) They are highly vital to the exploration of metals
(d) They can be reduced to sugar alcohols
Ans: (c)

• Monosaccharides Form a black residue of carbon when dehydrated
• they have a sweet taste
• they are reducing sugars.
• pure monosaccharides are water-soluble, white, crystalline solids

Q37: In the troposphere, the two types of pollutants are?
(a) Gaseous and particulate pollutants
(b) Carbon and metallic pollutants
(c) Natural and man-made pollutants
(d) Sulphuric and nitrogenous pollutants
Ans: (a)
The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur.
The gaseous and particulate pollutants in the troposphere include:

• Gaseous Pollutants: The oxides of nitrogen and sulphur, ozone, hydrocarbons, and several other oxidants in this category.
• Particulate Matter: viable particulates such as microorganisms like fungi and bacteria, non-viable particulate matter such as smoke.

Q38: The molar enthalpy change accompanying the removal of an electron from a gas phase atom or ion in its ground state is called?
(a) Electron gain enthalpy
(b) Ionization enthalpy
(c) Enthalpy change
(d) Enthalpic gas removal
Ans: (b)
The ionization enthalpy of an element is the amount of energy required to remove an electron from an isolated gaseous atom in its gaseous state.

Q39: The fourteen elements (atomic numbers 90-103) after actinium are called?
(a) Actinoids
(b) Nucleotides
(c) Pre-actinum elements
(d) Atomic elements
Ans: (a)
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium.

Q40: The process by which salt and water reacted in a limited way to form an acid or a base is?
(a) Neutral process
(b) Basic acidic process
(c) Hydrolysis
(d) Sublimation
Ans: (c)
Salt hydrolysis is a reaction in which one of the ions from a salt reacts with water, forming either an acidic or basic solution.