All Free Chemistry MCQs with Answers

• A. BaSO4
• B. SrSO4
• C. CaSO4
• D. MgSO4

Explanation: The solubility of Group 2 sulfates decreases as you move down the group from magnesium to barium.

• A. Fe>Sc>Rb>Br>Te>F>Ca
• B. Ca>Rb>Sc>Fe>Te>F>Br
• C. Rb>Ca>Sc>Fe>Br>Te>F
• D. Rb>Ca>Sc>Fe>Te>Br>F

Explanation: Alkali and alkaline earth metals are most electropositive. Alkali metals are more electropositive than alkaline earth metals.

• A. S2->Cl->K+>Ca2+
• B. Ca2+>K+>Cl->S2-
• C. Cl->S-2>Ca2+>K+
• D. K+>Cl->Ca2+>S2-

Explanation: Size of isoelectronic decreases with increase in atomic number. Therefore, option A is the correct answer.

• A. Alkali metals are at the maxima and noble gases at the minima.
• B. Noble gases are at the maxima and alkali metals at the minima.
• C. Transition element are at the maxima.
• D. Minima and maxima do not show any regular behaviour.

Explanation: In a period, alkali metals have the lowest and noble gases have the maximum ionisation energy.Hence, (b) is correct.

• A. atomic weight.
• B. nuclear weight.
• C. atomic numbers.
• D. neutron-proton ratios.

Explanation: The Modern periodic law states "The chemical and physical properties of elements are a periodic function of their atomic numbers".

• A. Mg(g)→ Mg+ (g) + e-
• B. Mg+(g)→ Mg2+(g) + e-
• C. Na(g) → Na+ (g)+ e-
• D. Na+(g) → Na+2(g) + e-

Explanation: Na+ has stable electronic configuration so removal of electron form Na+ to form Na+2 ion requires maximum energy.

• A. Generally reducing character of elements increases in period.
• B. Generally oxidising character of elements increases in period.
• C. Generally, basic character of oxides decreases in a group.
• D. All are correct.

Explanation: Oxidising character of elements increases in a period. Therefore option B is correct.

• A. It forms an basic oxide.
• B. It belongs to II A group.
• C. It belongs to IV period.
• D. It forms an acidic oxide.

Explanation: The element is calcium and hence its oxide (CaO) is basic in nature. So option D is correct.

• A. d5,d3,d1,d4 increasing magnetic moment.
• B. MO, M2O , MO2, M2O5 - decreasing basic strength.
• C. Sc, V, Cr, Mn - increasing number of oxidation states.
• D. Co2+,Fe3+,Cr3+,Sc3+ - increasing stability.

Explanation: d1 ,d3 ,d4 ,d5 - increasing magnetic moment.

• A. 1s2s22sp63s23p1
• B. 1s22s22p63s2
• C. 1s22s2sp63s1
• D. 1s22s2sp63s23p2

Explanation: Sodium has electronic configuration as 1s2 2s2 2p6 3s1. The last electron or the valence electron is in s orbital.

• A. Ionization enthalpy increases for each successive electron.
• B. The greatest increase in ionization enthalpy is experienced on removal of electron from core of noble gas configuration.
• C. End of valence electrons is marked by a big jump in ionization enthalpy.
• D. Removal of electron from orbitals bearing lower n value is easier than from orbital having higher n value.

Explanation: Removal of Electron from orbital bearing lower n value is difficult than from orbitals having higher n values. Option D is correct.

• A. 3, 11, 19, 37.
• B. 5, 13, 21, 39.
• C. 7, 15, 31, 49.
• D. 5, 13, 37, 49.

Explanation: Option D shows elements of group IIIA (5-Boron,13-Aluminum, 31-Gallium, 49-Indium. Hence option D is correct.

• A. IA.
• B. III A.
• C. III B.
• D. Zero Group.

Explanation: Group III B includes lanthanides and actinides and the total number of elements in this group = 32. Hence correct option is C.

• A. Small size
• B. High electronegativity
• C. Low ionization energy
• D. Large atomic radius

Explanation: Lithium and beryllium's small size and high charge density cause strong polarizing effects, leading to covalent bond formation and their…

• A. The properties of elements are periodic functions of their atomic numbers.
• B. Non-metallic elements are fewer in number than metallic elements.
• C. For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.
• D. The first ionisation enthalpies of elements generally increase with an increase in atomic number as we move along a period.

Explanation: Option C is the correct answer because it incorrectly states the order of filling for transition elements.

• A. Increases
• B. Decreases
• C. Constant
• D. None

Explanation: Across a period, added electrons enter the same principal shell, so the inner-shell electrons causing most shielding remain almost…

• A. Catenation is the main reason for large number of organic compounds
• B. The higher is the octane number, the better is quality of the petrol
• C. Reforming is done to increase the production of petrol
• D. Anthracite is the hardest form of coal

Explanation: Reforming is a process used in petroleum refining to convert low-octane hydrocarbons into high-octane hydrocarbons.

• A. Al2O3, SiO2, Fe2O3
• B. SiO2, K2O, Cr2O3
• C. Al2O3, SiO2, Cr2O3
• D. None of these

Explanation: The conversion of n-heptane to benzene is a process called aromatization. This involves the cyclic dehydrogenation of alkanes.

• A. 2
• B. -3
• C. 3
• D. 4

Explanation: The Dewar structure is an isomer of benzene where the six-membered ring is not planar and has a fused cyclobutene ring.

• A. CnH2n
• B. CnH2n-2
• C. CnH2n+2
• D. C2H2n-4

Explanation: The general formula CnH2n+2 is characteristic of saturated, open-chain hydrocarbons (alkanes).