Board Paper of Class 12-Science 2007 Chemistry (SET 1) - Solutions

State as a mathematical formula the de Broglie relationship for moving particles. What experimental evidence is available for this concept?

OR

Specify the ranges of values for quantum numbers m_land m_sfor an electron in an atom when the nquantum number value for it is 2. What is the significance of these values for the orbitals?

When can an endothermic process be spontaneous? Give an example of such a process.

Write balanced chemical equations for the following reactions:

(i)

(ii)

Explain any one of the following statements:

(i) The transition metals are well known for the formation of interstitial compounds.

(ii) The largest number of oxidation states are exhibited by manganese in the first series of transition elements.

Draw the three-dimensional representations of (R) - and (S) - butan- 2- ol.

Write chemical reaction equations to illustrate the following reactions:

(i) Williamson synthesis of ethers

(ii) Reimer−Tiemann reaction

Distinguish between addition polymers and condensation polymers and give one example of each class.

Answer the following in the light of MO theory:

(a) Which has a higher bond order, C₂ or ?

(b) Which species is not likely to exist, Li₂ or Be₂?

OR

(a) Compare the structural shapes of the following species:

SF₆ and SF₄

(b) What type of intermolecular forces exists between Cl₂ and CBr₄ present in a mutual solution?

(a) Name an element with which silicon can be doped to give an n-type semiconductor.

(b) Which type of crystals exhibits piezoelectricity?

The vapour pressure of water is 12.3 kPa at 300 K. Calculate the vapour pressure of a one molal solution of a non-volatile non-ionic solute in water.

Using the values of Δ_fH^Θand Δ_rS^Θ, given herein, calculate the standard molar Gibbs energy of formation, (Δ_fG^Θ) for CS₂(l). 

Given:

The rates of most reactions double when their temperature is raised from 298 K to 308 K. Calculate activation energy of such a reaction.

(R = 8.314 J mol⁻¹K⁻¹, log 2 = 0.3010)

State what is observed when

(i) the electrodes connected to a battery are dipped into a sol.

(ii) an electrolyte solution is added to a sol.

(iii) an emulsion is subjected to high-speed centrifugation.

Answer the following questions:

(i) Which element in the first series of transition elements does not exhibit variable oxidation states and why?

(ii) What happens when a solution of copper (II) sulphate is saturated with ammonia?

(iii) Why do actinoids, in general, exhibit a greater range of oxidation states than lanthanoids?

(a) Illustrate the following with an example each.

(i) Linkage isomerism

(ii) Coordination isomerism

(b) Why is paramagnetic? (Ni = 28)

Write the nuclear reactions for the following radioactive changes:

(i) undergoes α-decay

(ii) undergoes β-decay

(iii) undergoes K-decay

(You can put ‘X’ for the symbol which is not correctly known)

Explain the mechanism of nucleophilic addition to a carbonyl group and give one example of such addition reactions.

Write the chemical equations for the following chemical reactions:

(a) 1-Nitropropene is prepared from acetaldehyde

(b) Benzonitrile is converted into acetophenone

(c) A primary amine is prepared from a primary alkyl halide

Mention one important use of each of the following:

(i) Equanil

(ii) Sucralose

(iii) Carbon fibres

(a) Write the formulation for the galvanic cell in which the reaction,

takes place.

Identify the cathode and the anode reactions in it.

(b) Write Nernst equation and calculate the emf of the following cell:

OR

(a) Explain with one example each the terms weak and strong electrolytes.

(b) Write the Nernst equation and calculate the emf of the following cell:

(a) How would you account for any two of the following:

(i) PbO₂ is a stronger oxidising agent than SnO₂

(ii) H₃PO₂ acts as a monobasic acid.

(iii) The pKa value for HOCl is higher than that of HOClO

(b) Draw the structures of the following species:

(i) Peroxodisulphuric acid, H₂S₂O₈

(ii) Xenon tetrafluoride, XeF₄

OR

(a) Assign reasons for any two of the following observations:

(i) The lower oxidation state becomes more stable with increasing atomic number in Group 13.

(ii) Hydrogen iodide is a stronger acid than hydrogen fluoride in aqueous solution.

(iii) The basic character among the hydrides of Group-15 elements decreases with increasing atomic numbers.

(b) Draw the structural formula for XeOF₄.

(a) Name the three major classes of carbohydrates and give the distinctive characteristic of each class.

(b) What are nucleotides? Name two classes of nitrogen-containing bases found amongst nucleotides.

OR

(a) Describe the classification of lipids based on their chemical compositions. Mention the chief chemical characteristic of each class.

(b) Explain the term ‘mutarotation’.