Chemistry (Theory) 2015-2016 ISC (Commerce) Class 12 Question Paper Solution

Fill in the blanks by choosing the appropriate word/words from those given in the brackets: 

Ideal solutions obey ………. law and they …………. form azeotropic mixtures.

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm^-1, two, four, ohm^-1, cm², Cannizzaro, ohm^-1 cm^-1, zero, decreases, presence)

Fill in the blanks by choosing the appropriate word/words from those given in the brackets: 

Benzaldehyde undergoes ……….. reaction due to ………… of an α-hydrogen atom.

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm^-1, two, four, ohm^-1, cm², Cannizzaro, ohm^-1 cm^-1, zero, decreases, presence)

Fill in the blanks by choosing the appropriate word/words from those given in the brackets: 

The solubility of silver chloride ……… in the presence of sodium chloride because of ………..

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm^-1, two, four, ohm^-1, cm², Cannizzaro, ohm^-1 cm^-1, zero, decreases, presence)

Fill in the blanks by choosing the appropriate word/words from those given in the brackets: 

The unit of conductance is ………. and that of specific conductance is ………..

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm^-1, two, four, ohm^-1, cm², Cannizzaro, ohm^-1 cm^-1, zero, decreases, presence)

Fill in the blanks by choosing the appropriate word/words from those given in the brackets: 

When the concentration of a reactant of the first-order reaction is doubled, the rate becomes ……… times, but for ……….. order reaction, the rate remains the same.

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm^-1, two, four, ohm^-1, cm², Cannizzaro, ohm^-1 cm^-1, zero, decreases, presence)

The electrochemical equivalent is the amount of substance which gets deposited from its solution on passing electrical charge equal to:

 96,500 Coulombs

1 Coulomb

60 Coulombs

965 Coulombs

The complexion [Ni(CN)₄]^2- is:

 Square planar and diamagnetic

 Tetrahedral and Paramagnetic

Square planar and paramagnetic

Tetrahedral and Diamagnetic

Wohler’s synthesis is used for the preparation of:

Glycine

Amino acids

Urea

Proteins

When SO₂ gas is passed through the acidified K₂Cr₂O₇ solution, the colour of the solution changes to:

Red

Black

Orange

Green

In the equation \[\ce{CH3COOH + Cl2 ->[Red P][-HCl]A , the compound A is :}\]

CH₃CH₂Cl

ClCH₂COOH

 CH₃Cl

CH₃COCl

What is the order of reaction whose rate constant has the same unit as the rate of reaction?

What is the pH value of a solution whose hydroxyl ion concentration is 1 × 10^-2 M?

Calculate the number of coulombs required to deposit 5.4 g of Al when the electrode reaction
is: Al₃ + 3e^– + Al [Atomic Weight of Al 27 g/mol].

Write the reaction to prepare acetaldehyde from hydrogen gas and acid chloride.

The edge length of the unit cell of a body-centred cubic (bcc) crystal is 352 pm. Calculate the radius of the atom.

Match the following: 

A10% aqueous solution of cane sugar (mol. wt. 342) is isotonic with 1.754% aqueous solution of urea. Find the molecular mass of urea. 

The molecular weight of an organic compound is 58 g mol^-1. What will be the boiling point of a solution containing 48 grams of the solute in 1200 grams of water? 
[K_b for water = 0.513°C kg mole^-1; Boiling point of water = 100°C]

What will be the value of Van’t Hoff factor (i) of benzoic acid if it dimerises in aqueous solution? How will the experimental molecular weight vary as compared to the normal molecular weight? 

Determine the pH value of 0.001 M acetic acid solution if it is 2% ionised at this concentration. How can the degree of dissociation of this acetic acid solution be increased?

The solubility product of PbCl₂ at 298K is 1.7 × 10^-5. Calculate the solubility of PbCl₂ in g/lit. at 298K. 
Atomic Weights: [Pb = 207 and Cl = 35.5]

Graphite is anisotropic with respect to the conduction of electric current. Explain.

In a body centred and face centred arrangement of atoms of an element, what will be the number of atoms present in respective unit cells? Justify your answer with a calculation.

A compound AB has a simple cubic structure and has molecular mass 99. its density is 3.4 g cm^-3. What will be the edge length of the unit cell?

For the reaction :

\[\ce{2NO_{(g)} ⇌ N2_{(g)} + O2_{(g)}}\];

ΔH = -heat

K_c = 2.5 × 10² at 298K

What will happen to the concentration of N₂ if :

(1) Temperature is decreased to 273 K.

(2) The pressure is reduced

In a first-order reaction, 10% of the reactant is consumed in 25 minutes. Calculate:

(1) The half-life period of the reaction.

(2) The time required for completing 87.5% of the reaction.

Water acts as Bronsted acid as well as a Bronsted base. Give one example each to illustrate this statement.

i)

Consider the following cell reaction at 298 K: [3]
2Ag⁺ + Cd → 2Ag + Cd²⁺
The standard reduction potentials (E°) for Ag⁺/Ag and Cd^2-/Cd are 0.80 V and -0.40 V respectively:
(1) Write the cell representation.
(2) What will be the emf of the cell if the concentration of Cd²⁺ is 0.1M and that of Ag⁺ is 0.2 M?
(3) Will the cell work spontaneously for the condition given in (2) above?

(ii)

What is a buffer solution? How is it prepared? Explain the buffer action of a basic buffer with a suitable example.

Explain the following:

(i) When NaCl is added to the AgNO₃ solution, a white precipitate is formed.
(ii) An aqueous solution of ammonium chloride is acidic in nature.

A 0.05 M NH₄OH solution offers the resistance of 50 ohms to a conductivity cell at 298 K. If the cell constant is 0.50 cm-¹ and molar conductance of NH₄OH at infinite dilution is 471.4 ohm^-1 cm² mol^-1, calculate:
(i) Specific conductance
(ii) Molar conductance
(iii) Degree of dissociation

Write the IUPAC names of the following:

(i) [CO(NH₃)₄SO₄]NO₃

(ii) K[Pt(NH₃)Cl₃]

What type of isomerism is exhibited by the following pairs of compounds: 
(i)  [PtCl₂(NH₃)₄]Br₂ and [PtBr₂(NH₃)₄]Cl₂
(ii) [Cr(SCN)(H₂O)₅]²⁺ and [Cr(NCS)(H₂O)₅]²⁺

How does K₂[PtCl₄] get ionised when dissolved in water? Will it form a precipitate when AgNO₃ solution is added to it? Give a reason for your answer.

Give balanced equations for the following reactions: 

(i) Silver nitrate is added to the dilute solution of sodium thiosulphate.
(ii) Potassium dichromate is treated with acidified ferrous sulphate solution.
(iii) Phosphorus reacts with cone, sulphuric acid.

How will you obtain pure potassium permanganate (KMnO₄) crystals from its ore, pyrolusite? Give the steps involved and the reactions. 

(i)

Sulphur dioxide acts as an oxidizing agent as well as a reducing agent. Give one reaction each to show its oxidizing nature and its reducing nature.
(ii)

Explain why an aqueous solution of potassium hexacyanoferrate (II) does not give the test for ferrous ion.

What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements. 

How can the following conversions be brought about:

Acetaldehyde to acetaldehyde phenyl hydrazone.

How can the following conversions be brought about:

Benzoic acid to aniline.

How can the following conversions be brought about:

Methyl chloride to acetone.

How can the following conversions be brought about:

Benzene to benzene diazonium chloride.

Glycerol (propane 1,2,3 triol) is more viscous than ethylene glycol (ethane 1,2, diol). Explain

How can urea be detected by the Biuret test?

Identify the compound A,B and C:

\[\ce{C2H5OH->[PCl5]A->[KCN]B->[H3O+]C2H5COOH->[NH3][\Delta]C}\]

Identify the compound A,B and C:

\[\ce{C6H5COOH->[SOCl2]A->[NH3]B->[Br2/KOH]C}\]

Give a balanced equation for the following name reaction :

Benzoin condensation

Give a balanced equation for the following name reaction :

Wurtz-fitting reaction

Give a balanced equation for the following name reaction:

Carbylamine reaction

Give the chemical test to distinguish:

Formaldehyde and acetaldehyde

Give the chemical test to distinguish:

Dimethyl ether and ethyl alcohol.

Write the structure of three ethers with molecular formula C₄H₁₀O.

Starting with Grignard’s reagent, how will you prepare propanoic acid?

An organic compound A has the molecular formula C₇H₆O. When A is treated with NaOH followed by acid hydrolysis, it gives two products B and C. When B is oxidized, it gives A when A and C are each treated separately with PCl₅, they give two different products D and E.

(i) Identify A, B, C, D, and E.
(ii) Give the chemical reaction when A is treated with NaOH and name the reaction.

What do you observe when glucose solution is heated with Tollen’s reagent?

Name the monomers and the type of polymerisation in each of the following polymers:
(1) Terylene
(2) Polyvinylchloride

Give a balanced equation for the following reaction:

Ethylamine with nitrous acid.

Give a balanced equation for the following reaction:

Diethyl ether with phosphorus pentachloride.

Give the balanced equation for the following reaction:

Aniline with acetyl chloride