Board Paper of Class 12-Science 2004 Chemistry (SET 1) - Solutions

Explain Brownian movement.

Distinguish between reaction rate and reaction rate constant (specific reaction rate) of a reaction.

Write the cell reactions which occur in lead storage battery (i) when the battery is in use and (ii) when the battery is on charging.

Give chemical reaction in support of each of the following statements:

(i) The +1 oxidation state gets stabilised progressively from Ga to Ti in Group 13.

(ii) All the bonds in PCl₅ molecule are not equivalent.

Expand DDT. Write its structure.

Write the names of reagents and equations in the conversion of

(i) phenol to salicyl aldehyde

(ii) anisole to p-methoxyacetophenone

Write the modes of free-radical polymerisation of an alkene.

OR

Differentiate between addition and condensation polymers based on the mode of polymerisation. Give one example of each type.

Differentiate between Lanthanides and Actinides series.

Calculate the density of silver which crystallises in the face-centred cubic structure. The distance between the nearest silver atoms in this structure is 287 pm.

Two elements A and B form compounds having formula AB₂ and AB₄. When dissolved in 20 g of benzene (C₆H₆), 1 g of AB₂ lowers the freezing point by 2.3 Kwhereas 1.0 g of AB₄ lowers it by 1.3 K. The molar depression constant for benzene is 5.1 Kkg mol⁻¹. Calculate atomic masses of A and B.

Explain the Froth Floatation Method.

Conductivity of 0.00241 M acetic acid is 7.896 × 10⁻⁵ S cm⁻¹. Calculate its molar conductivity and if for acetic acid is 390.5 S cm² mol⁻¹, what is its dissociation constant?

A reaction is first order in A and second order in B.

(i) Write differential rate equation.

(ii) How is the rate affected if the concentration of B is tripled?

(iii) How is the rate affected when the concentrations of both A and B are doubled?

What is the significance of rate constant in the rate expression?

How are the colloids classified on the basis of the nature of interaction between dispersed phase and dispersion medium? Describe an important characteristic of each class. Which of these sols need stabilising agents for preservation?

Or

What are detergents? Give their scheme of classification. Why are the detergents preferred over soaps?

Draw a figure to show splitting of degenerate d orbitals in an octahedral crystal field. How does the magnitude of Δ₀ decide the actual configuration of d orbitals in a complex entity?

Explain the following terms with suitable examples:

(i) Frenkel defect

(ii) Interstitials

Draw the structures of monomers for the following polymers. Also draw the structures of the polymers and uses of:

(i) Teflon

(ii) PMMA

(iii) Buna-S

(a) Identify A and B in the following:

(i)

(ii)

Write the IUPAC names of the following:

(i)

(ii)

(iii)

(a) Assign appropriate reason for each of the following observations:

(i) Anhydrous AlCl₃ is used as a catalyst.

(ii) Phosphinic acid behaves as a monoprotic acid.

(iii) SF₆ is not easily hydrolysed whereas SF₄ is readily hydrolysed.

(iv) No form of elemental silicon is comparable to graphite.

(b) Draw the structure of XeOF₄ or BrF_3.

Or

Account for the following:

(i) Ammonia is a stronger base than phosphine

(ii) The tendency to exhibit +2 oxidation state increases with increasing atomic number in group 14.

(iii) HF is a weaker acid than HI.

(a) How would you account for the following:

(i) The transition elements exhibit high enthalpies of atomisation.

(ii) The 4d and 5d series of the transition metals have more frequent metal−metal bonding in their compounds than do the 3d metals.

(iii) There is a greater range of oxidation states among the actinoids than among the lanthanoids.

(b) Write the complete chemical equation for each of the following:

(i) An alkaline solution of KMnO₄ reacts with an iodide.

(ii) An excess of SnCl₂ solution is added to a solution of mercury (II)

Or

An aqueous solution freezes at 272.4 K, while pure water freezes at 273.0 K. Determine

(i) the molality of the solution

(ii) the boiling point of the solution

(iii) the lowering of vapour pressure of water at 298 K

[Given K_f = 1.86 K kg mol⁻¹, K_b= 0.512 K kg mol⁻¹ and vapour pressure of water at 298 K = 23.756 mm Hg]

Name the products obtained on complete hydrolysis of DNA. Enumerate the structural differences between DNA and RNA. In what way is a nucleotide different from a nucleoside? Illustrate with examples.

Or

Define and classify vitamins. Name the diseases caused due to lack of any three of them.