Maharashtra Board 12th Chemistry Exam 2025 : Most Important Question Answers for Last-Minute Revision

Maharashtra Class 12 exams have already begun and you have very little time left for the Chemistry exam. So, we are providing the most important answer type questions in this article. You can read them thoroughly and score good marks in your exams.

So this article is to help you with those most important MCQs and short question answers with quick and effective last-minute revision.

MCQs (Multiple Choice Questions) are an important part of your Chemistry exam to score good marks. Mastering them can boost your confidence and score significant marks.

These questions cover various topics from the syllabus of Chemistry. Remember, it is important to understand the logic behind each answer to score good marks.

Maharashtra Board Chemistry Most Important Question Answers

Multiple Choice Questions

1. n-type semiconductor is formed when trace amount of impurity is added to silicon. The number of valence electrons in the impurity atom must be.

(a) 3

(b) 5

(c) 1

(d) 2

Ans. (b) 5

2. The number of ions produced by the complex [Co(NH3)4CI2]CI is

(a) 1

(b) 2

(c) 3

(d) 4

Ans. (b) 2

3. The coordination number of atoms in body-centred cubic structure (bec) is

(a) 4

(b) 6

(c) 8

(d) 12

Ans. (c) 8

4. The substances which can be permanently magnetised are

(a) diamagnetic

(b) paramagnetic

(c) ferromagnetic

(d) nonmagnetic

Ans. (c) ferromagnetic

Maharashtra Board Class 12 Study Material

Maharashtra Board Class 12 Study Material
Syllabus	Maharashtra Board New Books
Model Paper	Revision Notes
Maharashtra Board Previous Year Paper

5. In calculating osmotic pressure, the concentration of solute is expressed in

(a) molarity

(b) molality

(c) mole fraction

(d) percentage mass

Ans. (a) molarity

6. The addition of the nonvolatile solute into the pure solvent

(a) increases the vapour pressure of solvent

(b) decreases the boiling point of solvent

(c) decreases the freezing point of solvent

(d) increases the freezing point of solvent

Ans. (c) decreases the freezing point of solvent

7. 10 ml of 0.1 M H₂SO₄, is mixed with 20 ml of 0.1 M KOH, the pH of resulting solution will be

(a) 0

(b) 7

(c) 2

(d) 9

Ans. (b) 7

8. If the hydrogen ion concentration changes by a factor of 1000, the value of its pH will

(a) decrease by 2 units

(b) decrease by 3 units

(c) increase by 1000 units

(d) increase by 2 units

Ans. (b) decrease by 3 units

9. Which of the following pairs is an intensive property ?

(a) Density, viscosity

(b) Surface tension, mass

(c) Viscosity, internal energy

(d) Heat capacity, volume

Ans. (a) Density, viscosity

10. The enthalpy of formation for all elements in their standard states is

(a) unity

(b) zero

(c) less than zero

(d) different elements

Ans. (b) zero

11. Two solutions have the ratio of their concentrations 0.4 and ratio of their conductivities 0.216. The ratio of their molar conductivities will be

(a) 0.54

(b) 11.574

(c) 0.0864

(d) 1.852

Ans. (a) 0.54

12. During the discharging of a lead storage battery,

(a) H₂SO₄, is consumed

(b) PbSO₄ is consumed

(c) Pb²⁺ ions are formed

(d) Pb is formed

Ans. (a) H₂SO₄, is consumed

13. The units of rate of a reaction and rate constant are same for a reaction of order

(a) zero

(b) one

(c) two

(d) fractional

Ans. (a) zero

14. The half-life of a first order reaction is 30 min and the initial concentration of the reactant is 0.1 M. If the initial concentration of reactant is doubled, then the half-life of the reaction will be

(a) 1800 s

(b) 60 min

(c) 15 min

(d) 900 s

Ans. (a) 1800 s

15. Among the known interhalogen compounds, the maximum number of atoms present is

(a) 3

(b) 6

(c) 7

(d) 8

Ans. (d) 8

16. The oxidation number of Xe in XeOF₂ is

(a) 0

(b) +2

(c) +4

(d) +3

Ans. (c) +4

17. Which one of the following elements belong to actinoid series?

(a) Cerium

(b) Lutetium

(c) Thorium

(d) Lanthanum

Ans. (c) Thorium

18. The total number of elements in each of f-series is

(a) 10

(b) 12

(c) 14

(d) 15

Ans. (c) 14

19. Magnetic moment of a metal complex is 5.9 B.M. Number of unpaired electrons in the complex is

(a) 2

(b) 3

(c) 4

(d) 5

Ans. (d) 5

20. Highest magnetic moment is shown by the ion

(a) V³⁺

(b) Co³⁺

(c) Fe³⁺

(d) Cr³⁺

Ans. (c) Fe³⁺ 

21. The number of unpaired electrons in a low spin octahedral complex ion of d' is

(a) 0

(b) 1

(c) 2

(d) 3

Ans. (b) 1

22. Ligand used in the estimation of hardness of water is

(a) EDTA

(b) DBG

(c) chloride

(d) bromo

Ans. (a) EDTA

23. Precipitation of protein is referred to as

(a) destruction of proteins

(b) separation of proteins

(c) denaturation of proteins

(d) fragmentation of proteins

Ans. (c) denaturation of proteins

24. Terylene is

(a) polyamide fibre

(b) polyester fibre

(c) vegetable fibre

(d) protein fibre

Ans. (b) polyester fibre

25. The constituents of carbon nanotubes are

(a) nanosized graphite sheets

(b) nanosized carbon black

(c) nanosized coal black

(d) None of the above

Ans. (a) nanosized graphite sheets

Very Short Answer Questions

Q1. What is valence band ?

Ans. Valence bond is a partially or completely filled band produced by bonding MOS, from which electrons can be promoted to conduction band.

Q2. What are ferromagnetic substances ?

Ans. The substances containing large number of unpaired electrons are strongly attracted by magnetic fields. These substances are called ferromagnetic substances.

Q3. What are hypotonic solutions?

Ans. Hypotonic solutions: When two solutions have differen osmotic pressures, then the solution having lower osmotic pressure is said to be a hypotonic solution with respect to the other solution.

Q4. Give an example of an ideal solution.

Ans. A liquid mixture of benzene and toluene which have nearly identical physical properties and intermolecular forces forms an ideal solution.

Q5. What is meant by conjugate acid-base pair ?

Ans. A pair of an acid and a base differing by a proton is called conjugate acid-base pair. For example, HCl and Cl-.

Q6. What is common ion effect ?

Ans. The ionization of a weak electrolyte is suppressed in presence of a strong electrolyte containing an ion common to the weak electrolyte.

Q7. What is thermodynamic equilibrium ?

Ans. A system is said to be in thermodynamic equilibrium when its state functions do not vary with time.

Q8. What is an intensive property ? Give an example.

Ans. Intensive property : It is a property of a system whose magnitude is independent of the amount of matter present in the system. For example, viscosity.

Q9. What are the functions of salt bridge ?

Ans. The functions of a salt bridge are :

(1) It maintains the electrical contact between the two electrod solutions of the half cells.

(2) It prevents the mixing of electrode solutions.

(3) It maintains the electrical neutrality in both the solutions of two half cells by a flow of ions.

(4) It eliminates the liquid junction potential.

Q10. What is conductivity ?

Ans. The reciprocal of resistivity is called conductivity. It is the conductance of a conductor of unit length and unit cross section area. OR It is the conductance of unit cube of material.

Q11. What is the rate constant of a reaction ?

Ans. Rate constant of the reaction is its rate when concentrations or partial pressures of all the reactants is unity.

Q12. What is the rate determining step of a chemical reaction ?

Ans. It is the slowest step in the mechanism of a complex reaction that occurs in more than one step.

Q13. What is the reaction intermediate in a complex reaction ?

Ans. The reaction intermediate is a species other than reactants or products produced in one step of the mechanism of a complex reaction and consumed in the subsequent step.

Q14. What are pseudo first order reactions ?

Ans. The reactions that have higher order true rate law but follow first order kinetics are called pseudo first order reactions.

Short Answer Type Question

1. Coordination number.

Ans. The number of the closest neighbouring constituent particles like atoms, ions or molecules which are in contact with a particular particle or an atom in the crystal lattice is called coordination number of that particle.

2. Osmosis.

Ans. It is defined as a spontaneous net flow of the solvent molecules from a pure solvent to a solution or from a more dilute solution to the more concentrated solution through a semipermeable membrane.

3. Buffer solution.

Ans. It is defined as a solution which resists the change in pH even after the addition of a small amount of a strong acid or a strong base or on addition of water.

4. Closed system.

Ans. It is defined as a system which can exchange only energy but not the matter with its surroundings.

5. Standard electrode potential.

Ans. It is defined as the difference of electrical potential between metal electrode and the solution around it at equilibrium when all the substances involved in the electrode reaction are in their standard states of unit activity or concentration at constant temperature.

6. Energy of activation.

Ans. It is the minimum kinetic energy possessed by the colliding reactant molecules leading to the formation of the products of the reaction

7. Coordination compound.

Ans. It is a compound in which central metal ion or atom is bound to surrounding atoms, molecules or anions called ligands by coordinate bonds.

8. Coordination sphere.

Ans. A coordination entity consisting of a central metal atom or ion and the ligands enclosed inside a square bracket is called coordination sphere.

9. Ligands.

Ans. The neutral molecules or negatively charged ions (or rarely positive ions) which are bonded by coordinate bonds to the central metal atom or metal ion in a coordination compound are called ligands.

10. Plane polarized light.

Ans. A light having oscillations only in one plane perpendicular to the direction of propagation of light is known as plane polarized light.

Short Answer Questions

Q1. What are Bravais lattices ?

Ans. (1) There are seven crystal systems according to the edges (a, b, c) and angles (α, β, γ).

(2) The constituents of the crystal may be present at corners, face centres, body centres, edge centres and voids.

(3) By mathematical analysis, it has been proved that only fourteen different kinds of space lattices are possible.

(4) Hence there are fourteen different ways of arrangement of the lattice basis.

(5) These fourteen lattices of seven crystal systems are called Bravais lattices.

Q2. What are the types of unit cells ?

Ans. Basically unit cells are of two types as follows :

(1) Primitive unit cell : The unit cell in which the constituent particles like atoms, ions or molecules are present only at the corners of the unit cell is called primitive unit cell or simple unit cell.

(2) Body-centred unit cell : A unit cell in which the constituent particles are present at the corners as well as at its body-centre is called body-centred unit cell.

(3) Face-centred unit cell : A unit cell in which the constituent particles are present at the corners as well as at the centre of each face is called face-centred unit cell or cubic close packed (CCP) unit cell.

(4) Base-centred unit cell : A unit cell in which the constituent particles are present at the corners as well as at the centres of two opposite faces is called end-centred or base centred unit cell.

Q3. What are semiconductors ? Explain intrinsic and extrinsic semiconductors.

Ans. Semiconductors : The substances like silicon, germanium which have poor electrical conductance at low temperature but the conductance increases with the increase in temperature are called semiconductors. Their conductivity lies between metallic conductors and insulators.

(a) Intrinsic semiconductor :

(i) A pure semiconductor material like pure Si, Ge which have a very low but finite electrical conductivity is called intrinsic semiconductor.

(b) Extrinsic semiconductor :

(i) Semiconductor doped with different element is called extrinsic semiconductor.

(ii) By doping with elements like Ga or P, the electrical conductivity is increased.

Q4. Explain the terms :

(1) Isotonic solutions

(2) (i) Hypotonic solutions (ii) Hypertonic solutions.

Ans.

(1) Isotonic solutions : The solutions having the same osmotic pressure at a given temperature are called isotonic solutions.

Explanation :

(i) For example, 0.1M urea solution and 0.1M sucrose solution are isotonic because they have the same osmotic pressure.

(ii) Isotonic solutions have the same molar concentration.

(iii) If isotonic solutions are separated by a semipermeable membrane, there is no flow of solvent in either direction.

(2) (i) Hypotonic solutions: When two solutions have different osmotic pressures, then the solution having lower osmotic pressure is said to be a hypotonic solution with respect to the other solution.

(ii) Hypertonic solutions: When two solutions have different osmotic pressures, then the solution having higher osmotic pressure is said to be a hypertonic solution with respect to the other solution. For example, if the osmotic pressure of sucrose solution is higher than that of urea solution then

(i) urea solution is hypotonic to the sucrose solution and

(ii) sucrose solution is hypertonic to urea solution.

Q5. Define buffer solution. What is buffer solution ? What are the types of buffer solution ?

Ans. Buffer solution : It is defined as a solution which resists the change in pH even after the addition of a small amount of a strong acid or a strong base or on dilution or on addition of water.

These are two types of buffer solution :

(A) Acidic buffer solution : It is a solution containing a weak acid (e.g. CH₃COOH) and its salt of a strong base. (e.g. CH₃COONa).

(B) Basic buffer solution : It is a solution containing a weak base (e.g. NH₄OH) and its salt of strong acid (e.g. NH₄CI).