Class 12 Chemistry: 200+ MCQs

• Bharat Panchali welcomes students to a video focusing on 200+ Class 12th Chemistry MCQs.
• The MCQs include previous year questions, assertion-reason questions, and sample paper questions.
• Practicing these MCQs is expected to significantly improve scores, potentially adding 20-25 marks, not just the 16 marks assigned to MCQs.
• Preparing with MCQs provides conceptual clarity, examples, and reasons that can aid in long answer writing, enhancing preparation beyond just MCQs.
• Notes used in the lecture will be available for free on the channel.

Resources Available on Bharat Panchali's Channel:

• 15-minute and 30-minute Revision Videos for quick reviews.
• Confidence Booster One Shots offering comprehensive chapter explanations.
• Mark Boost for previous year's questions.
• NCERT Diamond Question Series for essential NCERT questions.

Solutions Chapter - Important MCQs:

• The value of Henry's constant (K_H) increases with an increase in temperature.
• K_H value is directly proportional to temperature and inversely proportional to solubility.
• When ammonium chloride is dissolved in water at room temperature, the solution feels cool, indicating heat absorption.
• Salt dissolves more when ΔG0 (entropy increases), and temperature is high.
• Low oxygen concentration in blood tissues of people at high altitudes is due to low atmospheric pressure.
• To address the pressure-mole fraction problem for an unknown gas 'X' dissolved in water, use Henry's Law (P=K_H*x) to find the constant and solve for new conditions.
• Raoult's Law for a solution containing non-volatile solute is represented by p_1=p_1^0 x_1, where p_1 is the vapor pressure of the solvent, p_1^0 is the vapor pressure of the pure solvent, and x_1 is the mole fraction of the solvent.
• Ideal solutions are formed with similar intermolecular attractions, such as between n-hexane and n-heptane.
• Mixing acetone and chloroform results in negative deviation because of new hydrogen bond formation.
• With negative deviation both change in volume and change in enthalpy would be negative from raoult's law.
• Azotropic solutions with boiling points lower than either liquid exhibit positive deviation from Raoult's law.
• To calculate the boiling point of a solution, first use ΔT_b=K_b*m, where m is molality to find the boiling point elevation and then use the equation 𝑇_𝑏 = Δ𝑇_𝑏 + 𝑇_0𝑏, where T_0b is the boiling point of the pure solvent.
• In the freezing point depression graph, 'X' indicated the freezing point of solution.
• Isotonic solutions have the same osmotic pressure.
• Osmotic pressure is the preferred colligative property for determining molar masses of polymers and proteins due to room-temperature applicability and use of molarity.
• A raw mango placed in saline solution shrivels due to osmosis, not reverse osmosis.
• Osmotic pressure is a colligative property and is directly proportional to molarity.
• Molarity is temperature-dependent, while molality is not, as volume changes with temperature.
• Only four colligative properties are known: relative lowering in vapor pressure, elevation in boiling point, depression in freezing point, and osmotic pressure.
• Elevation in boiling point is a colligative property and is directly proportional to molality.
• Van't Hoff factor for KCl solution, assuming complete dissociation, approximates to 2.
• The solution showing the largest freezing point depression value is [Al_2(SO_4)_3] because it produces the most ions (highest Van't Hoff factor).
• Gases' solubility in liquid decreases with increasing temperature, because dissolution is an exothermic process based on Le Chatelier's principle.
• Raoult's Law states vapor partial vapor pressure for each solute, and only depends on the mole fraction of the pure solvent.
• Blood cells shrink when placed in a solution containing more than 0.9% NaCl due to osmosis.
• Number of moles can be obtained from mass of solute present divided by the molar mass of the element.
• Water retention or puffiness from high salt intake is due to osmosis.
• For temperature question, volume also doubles.

Electrochemistry:

• A galvanic cell behaves as an electrolytic cell when the external potential exceeds cell potential.
• When external potential is higher than the cell potential, it shows electrical behavior.
• In cell notation, oxidation is on the left, reduction is on the right, separated by a salt bridge.
• A standard electrode potential greater than zero implies the reduced form is more stable.
• For a spontaneous reaction, ΔG is negative, while E°_cell is positive.
• To calculate ECell with half-reactions, use: E°cell = E°reduction - E°oxidation, without multiplying half cell values with integers.
• On dilution, conductivity decreases, whilst molar conductivity increases, because the molar conductivity is inversely proportional to concentrations on dilution.
• Molar conductivity (Λ_m) is calculated as Λ_m=κ×1000/M.
• The unit for molar conductivity is Siemens cm^2 mol^-1.
• With electrolysis of aqueous NaCl, H2 is produced at the cathode (reduction), and Cl2 is produced at the anode (oxidation).
• Inverters commonly use the lead storage battery; Apollo space programs utilized the H_2O_2 fuel cell.
• With a Daniel cell (Zn/Cu), electron flow reverses from the cathode to the anode, when the E(ext) > 1.1 volts, otherwise there would be electrical current flowing from Cu to Zinc.
• Molarity cannot be a colligative property.
• Volume increases with temperature, leading to the statement: "the volume of solution changes with temperature".
• The correct value of the Van't Hoff factor can allow it to fully break down into its basic pieces, then the exact charge of the element can be obtained.
• Solubility decreases with increased temperature.

Chemical Kinetics:

• For reaction rates, ensure coefficients are used to represent rates (+1/2 dB/dt).
• In elementary reactions, doubling the concentration by a factor of 'n,' the rate equation will look like 〖Rate=k[A]^n〗.
• Do not guess orders from reactions, they must be determined experimentally from the law.
• At zero order reaction, the rate of the reaction is independent of the concentrations of reactants.
• Molecularity applies to elementary, but not complex reactions.
• For second-order kinetics, reducing reactant concentration to half decreases the rate to one-fourth (1/4).
• Catalysts alter activation energy.
• Temperature has to do with the fraction of molecules, or e^(-Ea/RT). "Fraction of Molecules."
• Reaction proceed faster with added catalyst as activation energy is lowered.
• To solve for questions involving graphs, create variables that are unknown to the user in order to solve, then plug back in.
• To simplify reactions with several substances, cut the number of substances in half to obtain easier data.
• Molecularity of a reaction can never be fraction.
• On concentration or rate of speed being equal, increasing order increases by X amount. For this example, it was increased by a power of 4.
• Zero order kinetics is: 𝑅_0−𝑅/𝑡. Make sure that 0 order must be in MOL/Time as rate is 1.
• For radioactive isotope questions, bigger rate constant lowers the half life.
• Arhenius equation is e=𝐾=𝐴𝑒^(−𝐸𝑎⁄𝑅𝑇). Know how to do it, as y=mx+b graph. If the line slopes down, the quantity would end up being negative.
• In a Daniel Cell, copper deposits at the copper terminal.
• Concentration reduces conductivity.
• For K_C, do not use large number when calculating the number of moles, cancel out in each case.

d- and f-Block Elements MCQs

• Formula for electrons: (n-1)d^(1 to 10)ns^(1 to 2).
• Mn exhibits the maximum number of oxidation states (+2 to +7) due to the involvement of both 4s and 3d electrons in bonding.
• Interstitial compounds add strength with new hardness.
• Zr and Hf possess similar atomic radii result in small magnitude difference.
• CuO2 is known as good catalyst properties with abilities for multiple oxidation states.
• Copper's most stable form is Cu^(+2), when Copper has a state of d^9 orbitals.
• For the "Concentrated Br(ine)", the following concentrated concentration of Na/OH is needed.
• Conductive properties means highest concentration. Check out the concentrations.
• Most common is +3 oxidation state with a lack of valence electrons.
• Actinium's shielding has bad properties by having electrons in the outer shells from the nucleus.
• Effect of an increase is effective nuclear charge.

Coordination Compounds:

• Reactions can yield byproducts: calculate which elements are required to form other molecules.
• EDTA is "Hexadentate Ligand" , with structure "Ethylene Diamine Tetra Acetate".
• Chelating complex is formed as a ring with two bonds within the structure.
• Oxidation state of central metal atom is equal to equal overcharge.
• The negative will indicate the strength of the acidity.
• Coordination number is just by the overall number of atoms in the organic compound.
• No bond is broken in a coordination sphere.
• In the formula, find the # of moles by finding oxidation states.
• If multiple bonds, create "Isomers".
• Nickel: Remember that high oxidation means strong.
• Crystal Field Splitting is 4/9 for tetrahedral.
• Number of charged moles can be obtained by breaking the molecule to its charges and ions, or by the negative charge from a negative atom in the end, like SO4.

Haloalkanes and Haloarenes:

• sP2 has a double bond and SP has a triple bond.
• Carbon is most stable, with halogens bound. SP2.
• Halogen Exchange: 〖RX+NaI→RI+NaX〗.
• Best synthesis : 〖RX+AgF→RF〗.
• For mono-substitution, find three different constitutional structures.
• Atack will take place in the "electrophilic substitution".
• Reactivity:
  • Mass increase on boil, but lower is better for substitutions.
  • Find SN1 reactions are tertiary carbon.
  • SN1 is two steps and racimization. Sn2 is one step with inversion.
• Check carbons with each unique molecule. Look for H, Br, CH3, CN, CL, then "yes".
• SN2; "1>2>3 for SN2"
• Enatiomer: 2-3 different properties.
• SN2 = substitution, and then look for least "substitutions."
• Strong nucleophilies will look for the highest concentration that favors the most stable version of the bond.
• Remember that when dealing with benzene (C6H6) or Phenol (benezine structure with other compounds in the end).
• Knoevenagel Condensation is where there is a basic and CN in the end.
• To determine the best way, try to solve what is the by-product and solve by the method.
• Look for ortho, meta, and para with different molecular and geometric patterns.
• Ether + HX - > AlkylHalides - > Alcohol. Carbocation -> 3
• 3 Carbon.

Alcohols, Phenols, and Ethers MCQs

• Naming is based on the order of priority: Alcohol > Ether > Alkyl.
• COH bond is less than "109.28"
• Phenols are more acidic.
• "Alkene is from 443 k" and "Ether is from 413-k"
• Strong bases will always win.
• CH ^"3 - CH -" "CH - CH - OH - " + H20
• Find a good acid.
• 2,3 vs other numbers: Use the rule.
• Hydrocation will result is 3-2-1 of best compounds, and is directly on oxidation rate.
• OH has - 471 to carbon, as bond order will allow high- strength, but low oxidation.
• Sn2, OH attack , look for "Williamson- Synthesis."
• Phenol : H+, then - 900+ and 500-.

Amines

• Reactions will be 2OH + N + Br.
• In the presence of "4 alkyl", it "runs" through the molecules.

Enhance your Class 12 Chemistry score with 200+ multiple-choice questions, including previous year, assertion-reason, and sample paper questions. These MCQs are designed to significantly improve understanding and boost scores by 20-25 marks. Free lecture notes are available for download.