Chemistry Board Sample Paper 2023-2024 Science (English Medium) Class 12 Question Paper Solution

Which of the following solutions will have the highest conductivity at 298 K? 

0.01 M HCl solution

0.1 M HCl solution

0.01 M CH₃COOH solution

0.1 M CH₃COOH solution

Identify A and B:

A = 1-phenylethanal , B = acetophenone

A = Benzophenone B = formaldehyde

A = Benzaldehyde , B = Acetophenone

A = Benzophenone, B = Acetophenone

The vitamins which can be stored in our body are ______.

Vitamin A, B, D and E

Vitamin A, C, D and K

Vitamin A, B, C and D

Vitamin A, D, E and K

What is IUPAC name of the ketone A, which undergoes iodo form reaction to give \[\ce{CH3CH = C(CH3)COONa}\] and yellow precipitate of \[\ce{CH3}\]?

3-Methylpent-3-en-2one

3-Methylbut-2-en- one

2, 3-Dimethylethanone

3-Methylpent-4-one

Which of the following is not correct?

In haloarenes, the electron pairs on halogen atom are in conjugation with π-electrons of the ring.

The carbon-magnesium bond is covalent and non-polar in nature. 

During `"S"_("N"^1)` reaction, the carbocation formed in the slow step being sp² hybridised is planar.

Out of \[\ce{CH2= CH-Cl and C6H5CH2Cl, C6H5CH2Cl}\] is more reactive towards `"S"_("N"^1)` reaction.

Match the properties with the elements of 3d series:

(i) (r), (ii) (q), (iii) (p)

(i) (r), (ii) (s), (iii) (p)

(i) (p), (ii) (q), (iii) (r)

(i) (s), (ii) (r), (iii) (p)

Which of the following statement is true?

Molecularity of reaction can be zero or a fraction.

Molecularity has no meaning for complex reactions.

Molecularity of a reaction is an experimental quantity.

Reactions with the molecularity three are very rare but are fast.

In which of the following solvents, the \[\ce{C4H8NH3+X–}\] is soluble?

ether

acetone

water

bromine water

Which of the following observation is shown by 2-phenyl ethanol with Lucas Reagent?

Turbidity will be observed within five minutes.

No turbidity will be observed.

Turbidity will be observed immediately.

Turbidity will be observed at room temperature but will disappear after five minutes.

If the initial concentration of substance A is 1.5 M and after 120 seconds the concentration of substance A is 0.75 M, the rate constant for the reaction if it follows zero-order kinetics is ______.

0.00625 molL^-1s^-1

0.00625 s^-1

0.00578 molL^-1s^-1

0.00578 s^-1

Anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron (III) bromide catalyst.

Due to the activation of benzene ring by the methoxy group.

Due to the de-activation of benzene ring by the methoxy group. 

Due to the increase in electron density at ortho and para positions.

Due to the formation of stable carbocation.

The trend of which property is represented by the following graph?

ionization enthalpy

atomic radii

enthalpy of atomization

melting point

Assertion (A): Alcohols react both as nucleophiles and electrophiles.

Reason (R): The bond between C–O is broken when alcohols react as nucleophiles.

Select the most appropriate answer from the options given below:

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Assertion (A): Strong oxidising agents oxidise toluene and its derivatives to benzoic acids.

Reason (R): It is possible to stop the oxidation of toluene at the aldehyde stage with suitable reagents.

Select the most appropriate answer from the options given below:

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false. 

A is false but R is true.

Assertion: Enzymes are very specific for a particular reaction and for a particular substrate.

Reason: Enzymes are biocatalysts.

Select the most appropriate answer from the options given below:

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false. 

A is false but R is true.

Assertion (A): During electrolysis of aqueous copper sulphate solution using copper electrodes hydrogen gas is released at the cathode.

Reason (R): The electrode potential of Cu²⁺/Cu is greater than that of H⁺/H₂.

Select the most appropriate answer from the options given below:

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Radioactive decay follows first-order kinetics. The initial amount of two radioactive elements X and Y is 1 gm each. What will be the ratio of X and Y after two days if their half-lives are 12 hours and 16 hours respectively?

The hypothetical reaction \[\ce{P + Q -> R}\] is half order w.r.t ‘P’ and zero order w.r.t ‘Q’. What is the unit of rate constant for this reaction?

A 5% solution of \[\ce{Na2SO4.10H2O}\] (MW = 3 22) is isotonic with 2% solution of non- electrolytic, non volatile substance X. Find out the molecular weight of X.

Arrange the isomeric dichlorobenzene in the increasing order of their boiling point and melting points.

Explain why the electrophilic substitution reactions in haloarenes occur slowly and require more drastic conditions as compared to those in benzene.

Out of p-tolualdehyde and p-nitrobenzaldehyde, which one is more reactive towards nucleophilic addition reactions, why?

Write the structure of the product formed when acetone reacts with 2, 4 DNP reagent.

Convert the following:

Benzene to m-nitrobenzaldehyde

Convert the following: 

Bromobenzene to benzoic acid

DNA fingerprinting is used to determine paternity of an individual. Which property of DNA helps in the procedure?

What structural change will occur when a native protein is subjected to change in pH?

Write the formula for the following coordination compound.

Bis (ethane-1,2-diamine) dihydroxidochromium (III) chloride

Does ionization isomer for the following compound exist? Justify your answer.

\[\ce{Hg[Co(SCN)4]}\]

Is the central metal atom in coordination complexes a Lewis acid or a Lewis base? Explain.

Can we construct an electrochemical cell with two half-cells composed of ZnSO₄ solution and zinc electrodes? Explain your answer.

Calculate the λ⁰m for Cl- ion from the data given below:

∧⁰m MgCl₂ = 258.6 Scm² mol^-1 and λ⁰m Mg²⁺ = 106 Scm² mol^-1

The cell constant of a conductivity cell is 0.146 cm^-1. What is the conductivity of 0.01 M solution of an electrolyte at 298 K, if the resistance of the cell is 1000 ohm?

Write the name of the reaction, structure and IUPAC name of the product formed when:

Phenol reacts with CHCl₃ in the presence of NaOH followed by hydrolysis.

Write the name of the reaction, structure and IUPAC name of the product formed when:

\[\ce{CH3CH2CH(CH3)CH(CH3) ONa}\] reacts with \[\ce{C2H5Br}\]

Write the name of the reaction, structure and IUPAC name of the product formed when:

CH₃CH₂CN reacts with stannous chloride in the presence of hydrochloric acid, followed by hydrolysis.

You are given four organic compounds “A”, “B” , “C” and “D”. The compounds “A”, “B” and “C” form an orange-red precipitate with 2, 4 DNP reagent. Compounds “A” and “B” reduce Tollen’s reagent while compounds “C” and “D” do not. Both “B” and “C” give a yellow precipitate when heated with iodine in the presence of NaOH. Compound “D” gives brisk effervescence with sodium bicarbonate solution. Identify “A”, “B”, “C” and “D” given the number of carbon atoms in three of these carbon compounds is three while one has two carbon atoms. Give an explanation for our answer.

When sucrose is hydrolysed the optical rotation values are measured using a polarimeter and are given in the following table:

1. Account for the two specific rotation values.
2. What is the specific name given to sucrose based on the above observation?
3. One of the products formed during the hydrolysis of sucrose is a glucose, that reacts with hydroxylamine to give compound A. Identify compound A.

An organic compound A with the molecular formula (+) C₄H₉Br undergoes hydrolysis to form (+) C₄H₉OH. Give the structure of A and write the mechanism of the reaction.

The rate constants of a reaction at 200 K and 500 K are 0.02 s^–1 and 0.20 s^–1 respectively. Calculate the value of Ea (Given 2.303 R = 19.15 JK^-1 mol^-1).

Read the passage carefully and answer the questions that follow.

Answer the following questions:

_(a) Out of ligands "A", "B", "C" and "D", which ligand causes maximum crystal field splitting? Why?

OR

Which of the two, “A” or “D” will be a weak field ligand? Why?

(b) Which of the complexes will be violet in colour? [CrA₆]^3- or [CrB₆]³⁺ and why?
(Given: If 560 - 570 nm of light is absorbed, the colour of the complex observed is violet.)

(c) If the ligands attached to Cr³⁺ ion in the complexes given in the table above are water, cyanide ion, chloride ion, and ammonia (not in this order).

Identify the ligand, write the formula and IUPAC name of the following:

1. [CrA₆]^3-
2. [CrC₆]³⁺

Read the passage carefully and answer the questions that follow.

Answer the following questions:

1. How many coulombs have been transferred from anode to cathode in order to consume one mole of sulphuric acid during the discharging of lead storage cell?
2. How much work can be extracted by using lead storage cell if each cell delivers about 2.0 V of voltage? (1 F = 96500 C)
3. Do you agree with the statement – “Hydrogen is a green fuel.” Give your comments for and against this statement and justify your views.

OR

Imagine you are a member of an agency funding scientific research. Which of the following projects will you fund and why?

1. safe recycling of lead batteries
2. extraction of hydrogen

Which of the following ions will have a magnetic moment value of 1.73 BM.

\[\ce{Sc^3+, Ti^3+, Ti^2+, Cu^2+, Zn^2+}\]

In order to protect iron from corrosion, which one will you prefer as a sacrificial electrode, Ni or Zn? Why? (Given standard electrode potentials of Ni, Fe and Zn are -0.25 V, -0.44 V and -0.76 V respectively.)

The second ionization enthalpies of chromium and manganese are 1592 and 1509 kJ/mol respectively. Explain the lower value of Mn.

Give two similarities in the properties of Sc and Zn.

What is actinoid contraction?

What causes actinoid contraction?

What is the oxidation state of chromium in chromate ion and dichromate ion?

Write the ionic equation for reaction of KI with acidified KMnO₄.

What is the effect of temperature on the solubility of glucose in water?

Ibrahim collected 10 mL each of fresh water and ocean water. He observed that one sample labeled “P” froze at 0° C while the other “Q” at -1.3° C. Ibrahim forgot which of the two, “P” or “Q” was ocean water. Help him identify which container contains ocean water, giving rationalization for your answer.

Calculate Van't Hoff factor for an aqueous solution of K₃ [Fe(CN)₆] if the degree of dissociation (α) is 0.852. What will be boiling point of this solution if its concentration is 1 molal? (Kb = 0.52 K kg/mol)

What type of deviation from Roult’s Law is expected when phenol and aniline are mixed with each other? What change in the net volume of the mixture is expected? Graphically represent the deviation.

The vapour pressure of pure water at a certain temperature is 23.80 mm Hg. If 1 mole of a non-volatile non-electrolytic solute is dissolved in 100g water, Calculate the resultant vapour pressure of the solution.

An organic compound with molecular formula \[\ce{C7H7NO2}\] exists in three isomeric forms, the isomer ‘A’ has the highest melting point of the three. ‘A’ on reduction gives compound ‘B’ with molecular formula \[\ce{C7H9N}\]. ‘B’ on treatment with \[\ce{NaNO2/HCl}\] at 0-5° C to form compound ‘C’. On treating C with \[\ce{H3PO2}\], it gets converted to D with formula \[\ce{C7H8}\], which on further reaction with \[\ce{CrO2Cl2}\] followed by hydrolysis forms ‘E’ \[\ce{C7H6O}\]. Write the structure of compounds A to E. Write the chemical equations involved.

Account for the following:

N-ethylbenzene sulphonyl amide is soluble in alkali.

Account for the following:

Reduction of nitrobenzene using Fe and HCl is preferred over Sn and HCl.

Arrange the decreasing order of pKb values.

\[\ce{C6H5NH2, C6H5NHCH3, C6H5CH2NH2, CH3NH2, NH3}\]

Arrange the increasing order of solubility in water.

\[\ce{C2H5Cl, C2H5NH2, C2H5OH}\]

Arrange the decreasing boiling point.

\[\ce{CH3COOH, C2H5OH, CH3NH2, CH3OCH3}\]