Class 12 ISC Chemistry Specimen 2023

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

[two, Williamson’s synthesis, three, anisole, toluene, Friedel-Crafts alkylation, iodoform, sec^-1 , mol^-1L sec^-1 , Lewis base, acetone, Lewis acid, chloroform, formaldehyde]

(i) Sodium phenoxide reacts with methyl chloride to give _______. The reaction is known as ________.

Solution

Anisole, Williamson’s synthesis

(ii) When the concentration of a reactant of first order reaction is tripled, the rate of reaction becomes ________ times. The unit of rate constant (k) for the first order reaction is ________.

Solution

3times,second^-1

(iii) In coordination complexes, the central metal atom or ion behaves as ________ and the ligands behave as ________.

Solution

Lewis acid/Lewis bases

(iv) Calcium acetate on dry distillation gives ________ which gives _______ on heating with iodine and alkali.

Solution

Acetone/Iodoform

Select and write the correct alternative from the choices given below:

(i) An alkyl isocyanide on complete reduction gives :

1. Primary amine.
2. Secondary amine.
3. Tertiary amine.
4. Carboxylic acid.

Solution

(b) Secondary amine

(ii) For a spontaneous reaction E° cell and ∆G° will be respectively

1. -ve and -ve
2. -ve and +ve
3. +ve and -ve
4. +ve and +ve

Solution

(b)-ve and +ve

(iii) Which of the following pairs of transition elements have exceptional electronic configuration?

1. Sc and Cu
2. Fe and Ni
3. Cr and Cu
4. Mn and Zn

Solution

(c)Cr and Cu

(C)

Solution

(D)(i) Assertion: Specific conductance of all electrolytes decreases on dilution.
Reason: On dilution, number of ions per unit volume decreases.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation for assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

Solution

(D)(ii) Assertion: Nitration of chlorobenzene leads to the formation of m-nitro chlorobenzene
Reason: : Nitro (-NO₂) group is a m-directing group
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation for assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

Solution

Q2 The osmotic pressure of 20g haemoglobin in 500ml of solution is 0·016atm at 25°C. Calculate the molecular mass of haemoglobin.

Solution

Q3 Give reason for the following:

(i) Transition metals form large number of complex compounds.
(ii) Transition elements show variable oxidation states.

Solution

Q4 Identify compounds [A] and [B] in the following reactions.

Solution

Q5 State reasons for the following:

(i) Ethylamine is soluble in water whereas aniline is not soluble in water.
(ii) Aliphatic amines are stronger bases than aromatic amines.

Solution

Q6 Calculate the standard free energy change (∆G° ) for the following chemical reaction:

Solution

Q7 Complete and balance the following chemical equations

Solution

Q8 (i) How will the following be obtained? (Give chemical equation)

(a) Picric acid from phenol
(b) Ethanol from formaldehyde.

Solution

Q8(ii) Write the chemical equations for the dehydration of ethanol with conc. H2SO4 at 140°C and 170°C

Solution

Q9 A solution of urea in water has boiling point 100·128°C. Calculate the freezing point of the same solution. Molal constants for water are K_b = 0·512 K kg mol^-1 and Kf = 1·86 K kg mol^-1 respectively.

Solution

Q10 Give one chemical test for each to distinguish between the following pair of compounds.

(i) Formaldehyde and acetic acid
(ii) Acetaldehyde and acetone

Solution

Q11 Why are Zn, Cd and Hg not regarded as transition elements?

Solution

Q12 The rate constant for a first order reaction becomes six times when the temperature is increased from 350 K to 410 K. Calculate activation energy (Ea) for the reaction.

Solution

Q13 An organic compound ‘A’ on treatment with aq.KCN produces compound ‘B’. Compound ‘B’ on reduction with Na/C2H5OH gives compound ‘C’ with molecular formula C2H7N. Compound ‘C’ reacts with NaNO2 and HCl to form compound ‘D’. Compound ‘D’ on treatment with acetic acid in presence of conc. H2SO4 produces a sweet smelling compound ‘E’.
(i) Identify the compounds ‘A’ to ‘E’.
(ii) Name the reaction for the formation of compound ‘E’ from compound ‘D’.

Solution

Q14 (i) Name the four bases present in DNA. Which one of these is not present in RNA?

(ii) Deficiency of which vitamin causes the following diseases.
(a) Scurvy (b) Night blindness

Solution

Q15 An aqueous solution containing 12·48g of barium chloride in 1000g of water boils at 373·0832K. Calculate the degree of dissociation (α) of barium chloride. K_b for H₂O = 0·52K kg mol^-1 , molecular mass of BaCl₂ = 208·34 g mol^-1

Solution

Q16 Write the chemical equation for the following named organic reactions.

(i) Haloform reaction
(ii) Reimer - Tiemann reaction
(iii) Kolbe - Schmidt reaction or Kolbe reaction

Solution

Q17 (i) Identify the compounds A, B and C in the following reactions:


OR

(ii) How will the following be converted? (Give chemical equations)

(a) Benzenediazonium chloride to Benzene
(b) Ethylamine to ethyl alcohol
(c) Methylamine to methyl isocyanide

Solution

Q18 Suppose 50 bacteria are placed in a flask containing nutrients, so that they can multiply. A study at 35° C gave the following results:



Answer the following questions:

(i) This multiplication of bacteria follows:
(a) Zero order reaction
(b) First order reaction
(c) Second order reaction
(d) Third order reaction

(ii) The rate constant for the reaction is:
(a) 0·0462 min^-1
(b) 0·462 min^-1
(c) 4·62 min^-1
(d) 46·2 min^-1

(iii) The half life period (t_1/2) of the reaction is:
(a) 1500 minutes
(b) 150 minutes
(c) 15 minutes
(d) 1·5 minutes

Solution

Q19(i) Starting with methyl magnesium bromide, how will the following compounds be synthesised?
(a) Acetaldehyde
(b) Acetone
(c) Acetic acid

Solution

Q19(ii) Explain the following:
(a) Chloroacetic acid is stronger acid than acetic acid.
(b) Formic acid reduces Tollen’s reagent but acetic acid does not.

Solution

Q20 (i) Name the type of isomerism shown by the following pairs of coordination compounds.


(ii) Consider the complex ion [Co(CN)₆]^3- and answer the following questions:
(atomic number of Co = 27)
(a) Type of hybridisation of central metal atom
(b) Magnetic nature
(c) Geometry of the complex ion
(d) Low spin complex or high spin complex

Solution

Q21 (i) A 0·06 molar CH₃COOH solution offers a resistance of 55 ohms to a conductivity cell at 25°C. If the cell constant is 0·45cm^-1 and the molar conductance of CH₃COOH at infinite dilution is 398·5 ohm^-1 cm²mol^-1 . Calculate:
(a) Specific conductance
(b) Molar conductance
(c) Degree of dissociation

Calculate the number of coulombs of charge required to deposit 24·35g of aluminium from a solution containing Al³⁺ ions.
(Atomic weight of Al = 27)

Q21(ii) (i)Write the Nernst equation for the cell reaction given below and calculate the emf of the cell at 298K.


Calculate the molar conductance at infinite dilution (ꓥ^∞_m) for NH₄OH. Given that ꓥ^∞_m for Ba(OH)₂, BaCl₂ and NH₄Cl are 457 ohm^-1cm²mol^-1,240 ohm^-1cm²mol^-1and 129 ohm^-1cm²mol^-1 respectively.
Solutions