All Free Chemistry MCQs with Answers

• A. Chlorine
• B. Bromine
• C. Fluorine
• D. Iodine

Explanation: Teflon is a synthetic fluoropolymer, meaning it is a polymer made up of repeating units containing fluorine atoms.

• A. Iodine
• B. Bromine
• C. Chlorine
• D. Fluorine

Explanation: Iodine (I) has the largest atomic size among the given halogens. As atomic size increases, the outermost electrons are farther from the…

• A. Salt formers
• B. Rare earth elements
• C. Alkali metals
• D. Noble gases

Explanation: Halogens are known as salt formers because they react with metals to form salts.

• A. MnO2
• B. PbO2
• C. BaO2
• D. None of the above

Explanation: Hydrogen peroxide (H₂O₂) is formed by the reaction of an acid with a peroxide.

• A. 1 : 1
• B. 1 : 2
• C. 2 : 1
• D. 9 : 4

Explanation: The balanced chemical equations are Zn + H₂SO₄ → ZnSO₄ + H₂ and Zn + 2NaOH → Na₂ZnO₂ + H₂.

• A. Number of electrons
• B. Number of neutrons
• C. Number of paired electrons
• D. Number of protons

Explanation: Melting and boiling points generally increase with the number of electrons, because more electrons lead to stronger London dispersion (van…

• A. KI + HCl
• B. O3
• C. PbS
• D. Na2SO3

Explanation: Ozone (O₃) is a much stronger oxidizing agent than hydrogen peroxide (H₂O₂).

• A. HgS
• B. PbS
• C. NiS
• D. CuS

Explanation: Lead(II) sulfide (PbS) is a black solid. Hydrogen peroxide oxidizes it to lead(II) sulfate (PbSO₄), which is a white solid, via the…

• A. NaOH
• B. Mg(OH)2
• C. NH4OH
• D. All are equally strong

Explanation: Sodium hydroxide (NaOH) is the strongest base among the options because it is the hydroxide of a Group 1 alkali metal.

• A. CO + H2
• B. CO + N2
• C. CO + H2 + N2
• D. None of the above

Explanation: Semi-water gas is produced when a mixture of steam and air is passed over hot coke.

• A. NaH
• B. CaH2
• C. SrH2
• D. AsH3

Explanation: Covalent hydrides are formed when hydrogen bonds with nonmetals or metalloids.

• A. B2H6
• B. NH3
• C. H2O
• D. CH4

Explanation: Electron-precise hydrides have just enough electrons to form normal single bonds-no shortage, no extra lone pairs.

• A. Hydrogen can be fused to form helium
• B. Helium can be fused to form hydrogen
• C. Helium dissociate to form hydrogen
• D. None of these

Explanation: Under the extreme conditions of temperature and pressure found in the cores of stars, nuclear fusion occurs.

• A. Copper
• B. Zinc
• C. Iron
• D. Both b and c

Explanation: A metal will displace hydrogen from a dilute acid if it is more reactive than hydrogen (i.e., higher in the electrochemical series).

• A. Addition of ice cold H2SO4 on BaO2
• B. Addition of ice cold H2SO4 on PbO2
• C. Aerial oxidation of 2 ethyl anthraquinol
• D. Electrolysis of (NH4)2SO4 at a high current density

Explanation: Lead dioxide (PbO₂) is not a peroxide but a true oxide of lead in the +4 oxidation state.

• A. Almost pure water
• B. Almost pure hydrogen peroxide
• C. A mixture of water and hydrogen peroxide
• D. None of these

Explanation: Atomic hydrogen reacts with O₂ stepwise (H· → HO₂· → H₂O₂), and this pathway strongly favors hydrogen peroxide formation.

• A. Saturation of water with MgCO3
• B. Saturation of water with CaSO4
• C. Addition of Na2SO4 to water
• D. Saturation of water with CaCO3

Explanation: Hardness in water is caused by the presence of dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions.

• A. CO and H2 are fractionally separated using Copper Chloride solution
• B. CO is removed by absorption in aqueous Cu2Cl2 solution
• C. H2 is removed through occlusion with Pd
• D. CO is oxidized to CO2 with steam in the presence of a catalyst followed by absorption of CO2 in an alkaline solution

Explanation: This describes the water-gas shift reaction. The initial mixture is treated with steam over a catalyst to convert the toxic CO into CO₂…

• A. Its tendency to lose an electron to form a cation
• B. Its tendency to gain a single electron in its valence shell to attain stable electronic configuration
• C. Its electron-gain enthalpy value is low, i.e. only slightly negative
• D. Its small size

Explanation: The most significant similarity between hydrogen and the halogens is their electronic structure.

• A. The ionization enthalpy of hydrogen resembles that of the alkali metals
• B. Its reactivity is similar to halogens
• C. It resembles both alkali metals and halogens
• D. Loss of an electron from a hydrogen atom results in a nucleus of a very small size

Explanation: A hydrogen ion (H⁺) is a bare proton with no electrons. This gives it an incredibly small size and a very high positive charge density.