Chemistry – Free Online JAMB CBT Practice quiz 2025

Propyne (methylacetylene) is an alkyne with the chemical formula HC≡CCH3

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.

A  mixture is a material made up of two or more different chemical substances which are not chemically combined. 

Mercury is a chemical element with the symbol Hg and atomic number 80.

Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest halogen and is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour.

Atomic weight, also called relative atomic mass, ratio of the average mass of a chemical element's atoms to some standard.

Carbon dioxide, a colorless gas having a faint sharp odor and a sour taste. It is a greenhouse gas.

Global warming occurs when carbon dioxide (CO2) and other air pollutants collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth’s surface. Normally this radiation would escape into space, but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. These heat-trapping pollutants—specifically carbon dioxide, methane, nitrous oxide, water vapor, and synthetic fluorinated gases—are known as greenhouse gases, and their impact is called GREENHOUSE EFFECT

Kerosene contains hydrocarbon with twelve to eighteen carbon atoms per molecule.

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state.

Familiar substances that sublime readily include iodine, dry ice, menthol, and

The N shell is the fourth orbit with 32 max number of electrons using 2n².

- 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.

- Calcium trioxocarbonate (IV) occurs abundantly in earth's crust as limestone, chalk and marble

- Eggshell is made almost entirely of calcium carbonate (CaCO3) crystals.

Since the surface tension forces become smaller as the distance between water molecules increases, the intervening soap molecules decrease the surface tension.

fluorine (F), most reactive chemical element and the lightest member of the halogen elements.

 As the most electronegative element, it is extremely reactive.

mass number, is the sum of the numbers of protons and neutrons present in the nucleus of an atom.

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.

One mole of carbon dioxide molecules has a mass of 44.01 g, 

: 5  mole of carbon dioxide molecules has a mass of 220g

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.

Heat capacity or thermal capacity: The amount of heat to be supplied to an object to produce a unit change in its temperature(1k).

The most abundant naturally occurring gas is Nitrogen (N2), which makes up about 78% of air. Oxygen (O2) is the second most abundant gas at about 21%. The inert gas Argon (Ar) is the third most abundant gas. 

Argon is the most abundant rare gas in the atmosphere. It is represented by the symbol Ar. The atomic number of Ar is 18.

The hydrogen atom is the simplest of all atoms: it consists of a single proton and a single electron.

The ideal metals to use for the task of recovering copper from an aqueous solution of copper sulphate are metals that are stronger reducing agents than copper but not reactive enough to react with the water that the solution consists of.

 Zinc, Aluminium, Iron are relatively inexpensive and being unreactive on exposure to water.

An atom nucleus is made up of protons and neutrons.

An electron is a negatively charged subatomic particle that orbits the nucleus of an atom

The Group 7 elements are called the halogens. They are placed in the vertical column, second from the right, in the periodic table . 

Chlorine (17), bromine(35) and iodine(53) are the first three of the Group 7 elements.

Reduction, any of a class of chemical reactions in which the number of electrons associated with an atom or a group of atoms is increased.

Redox (reduction/oxidation) describes all chemical reactions in which atoms have an increase or decrease in oxidation number (oxidation state).

An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula.

metallurgy, art and science of extracting metals from their ores and modifying the metals for use. 

A hydrocarbon is any of a class of organic chemicals made up of only the elements carbon (C) and hydrogen (H).

Classes are Aliphatic and Aromatic Hydrocarbons.

Natural sources are coal, natural gas and petroleum.

 Monosaccharides are reducing sugars.

- Pure monosaccharides are water-soluble, white, crystaline solids.

- They taste sweet

- Form a black residue of carbon when dehydrated

The troposphere is the first and lowest layer of the atmosphere of the Earth.

- Gases mix at this layer.

- Weather occurs here

- Region where plants and animals breathe and live

- Tropospheric pollution is caused due to the presence of unwanted gaseous or solid components in the air.

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.

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.

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.

Fractional distillation is used to separate mixtures into its component parts or fractions with the difference in boiling points between successive fractions must be more than 10°C. An example is the liquid nitrogen and oxygen are then separated by fractional distillation.

Duralumin is an alloy made up of 90% aluminum, 4% copper, 0.51% magnesium, and less than 1% manganese.

Polysaccharides are long chains of monosaccharides linked by glycosidic bonds. Three important polysaccharides, starch, glycogen, and cellulose, are composed of glucose.

Sulfuric acid is flushed with a mild, soapy solution if the burns are not severe. Sulfuric acid feels hot when water is added to the acid, but it is better to flush the area and not leave the acid on the skin.

Don't try to neutralize the burn with acid or alkali. This could cause a chemical reaction that worsens the burn.

The element with atomic number 17 is Chlorine with a valency of -1, that is it needs to receive an electron or possibly lose seven electrons to obey the octet rule.

Sulfuric acid is flushed with a mild, soapy solution if the burns are not severe. Sulfuric acid feels hot when water is added to the acid, but it is better to flush the area and not leave the acid on the skin.

Don't try to neutralize the burn with acid or alkali. This could cause a chemical reaction that worsens the burn.

Destructive distillation of a tonne of coal can produce 700 kg of coke, 100 liters of liquor ammonia, 50 liters of coal tar and 400 M3 of coal gas.

A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a 

strong alkali which is highly soluble in water producing caustic basic solutions / an alkaline solution that is used to make soaps. "Lye" most commonly refers to sodium hydroxide (NaOH), but historically has been used for potassium hydroxide (KOH).

A Mixture contains two or more constituents which can be easily separated by physical methods. Examples include Air, Soil, Palm oil, Sea water, Blood, Crude oil, etc

The reaction of calcium carbide with water, 

producing acetylene and calcium hydroxide, was discovered by Friedrich Wöhler in 1862. This reaction was the basis of the industrial manufacture of acetylene, and is the major industrial use of calcium carbide.

They are the most stable due to having the maximum number of valence electrons their outer shell can hold. Therefore, they rarely react with other elements since they are already stable.

NH4NO3 Ammonium Trioxonitrate(V) , unlike all other metallic trioxonitrates(v), decomposes on heating to give nitrogen(i)oxide N2O and water

Nitrogen(I)Oxide rekindles a brightly glowing splinter but extinguishes a feebly glowing one which is not hot enough to decompose the gas to liberate oxygen.

The ammonia molecule has a trigonal pyramidal shape with the three hydrogen atoms and an unshared pair of electrons attached to the nitrogen atom.

The addition of conc HCL makes the solution more acidic and the solution falls below the original value

Deliquescence, the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution. Deliquescence occurs when the vapour pressure of the solution that is formed is less than the partial pressure of water vapour in the air. A particular example of hygroscopic behavior is deliquescence which is exhibited by many water-soluble solids, including inorganic salts (e.g., calcium chloride).

Helium floats because it is buoyant; its molecules are lighter than the nitrogen and oxygen molecules of our atmosphere and so they rise above it

One of the several uses of sulfur is for the vulcanization of rubber.

Tetrachloromethane ( carbon tetrachloride) is an effective solvent within the chemical industry and is used to clean 

machinery and electrical equipment. 

I.e as a solvent for oils, fats, lacquers, varnishes, rubber waxes, and resins, and as a grain fumigant.