Chemistry (Class XII) Upload Date: 25-08-2011 Assignment By : Mr.Imendra Yadav

Surface ChemistryQ.1 How does chemical adsorption of a gas on a solid vary with temperature?Q.2 How does addition of alum purifies water?Q.3 How is dialysis carried out? Mention its one application.Q.4 Name two industrial processes in which heterogeneous catalysts are employed.Q.5 Define ultrafilteration?Q.6 Taking two examples of heterogeneously catalytic reactions, explain how a heterogeneous catalyst helps in the reaction?Q.7 What is the difference between a colloidal solution and an emulsion? Give an example of each type. What is the role of emulsifiers in forming emulsion?Q.8 State Hardy-Schulze rule. Give reasons for development of charge on colloidal particles.Q.9 What is the sign of ΔH and ΔS when Bromine gas gets adsorbed on charcoal?Q.10 Give a method of preparation ruby red sol of Au.Q.11 What observed when the electrodes connected to a battery are dipped in to a sol.Q.12 Lyophilic colloid is more stable than lyophobic colloid. Explain.Q.13 Explain the following: 1.) Coagulation takes place when NaCl solution is added to a colloidal sol. ferric hydroxide. 2.) Sky appears blue in colour.Q.14 How does BF3 act as a catalyst in industrial process?Q.15 Give two examples of shape selective catalysis.Q.16 State the principle of electro dialysis.Q.17 What is the adsorption isotherm?Q.18 Distinguish between Freundlich adsorption isotherm and Langmuir adsorption isotherm with the help of appropriate graphs.Q.19 Which one of the following electrolytes is most effective for the coagulation of Fe (OH)3 sol and why? NaCl, Na2SO4, Na3PO4Q.20 What is meant by ‘Shape Selective Catalysis’? How is it used in obtaining gasoline from alcohol? Name the catalyst used in this process.

Chemistry (Class XII) General Principles and Processes of Isolation of Elements

Q.1 What are depressant? How would separate CuS and lead sulphide?Q.2 Why is it advantageous to roast a sulphide ore to oxide before reduction?Q.3 Name a metal which purified by vapour phase refining?Q.4 Why is calcocite roasted and not calcinated in recovery of copper?Q.5 Is it true that under certain condition Mg can reduce Al2O3 and Al can reduce MgO? What are those conditions?Q.6 Explain why reduction of Cu2O is much easier than that of Fe2O3?Q.7 Outline the principles of refining of metals by the following methods: 1.) Zone refining 2.) Electrolytic refining 3.)Vapour Phase refiningQ.8 What is the role of graphite rod in the electrometallurgy of Al?Q.9 What is the role of cryolite in the metallurgy of Al?Q.10 State the role Si in the metallurgy of Cu?Q.11 Give one example of the following for extraction of metal: 1.) Auto-reduction 2.) H2 is used as reducing agentQ.12 How is chemical reduction different from electrolytic reduction? How is Ag obtained from argentite? Give chemical reactions involved.Q.13 Write short notes on the following: 1.) Magnetic separation 2.) Aluminothermic process 3.) LiquationQ.14 The choice of reducing agent in a particular case depends on the thermodynamic factor. How far do you agree with this statement? Support your opinion with two examples.Q.15 Copper can be extracted by hydrometallurgy but not Zinc. Explain.Q.16 Why is the extraction of Cu from pyrite difficult than that from its oxide ore through reduction?Q.17 Discuss some of the factors which need consideration before deciding extraction of metal from its ore?Q.18 Indicate the temperature at which C can be used as reducing agent of FeO?Q.19 What metals are extracted by the electrolytic process? What positions do these metals occupy in the periodic table?Q.20 Carbon monoxide is more effective agent than C below 983K but above this temperature the reverse is true. Explain.

Chemistry (Class XII)

The p-block elementsQ.1 In solid state PCl5 behaves as an ionic species. Give reasons.Q.2 Among the noble gases only Xenon is well known to form chemical compounds.Why?Q.3 Write one chemical equation to show that SO2 acts as a reducing agent.Q.4 Write the chemical equations for the reactions which occur when: Sodium iodate[NaIO3] is reduced with sodium hydrogrn sulphite.Q.5 Draw the structure of XeF4.Q.6 Why is bond dissociation energy of fluorine moleucle less than chlorine molecule?Q.7 Why is hydrogen sulphide, with greater molar mass, a gas, while water a liquid at room temperature?Q.8 Explain the following observation in terms of VB theory: Both SiF62- and SF6 are octahedral structures.Q.9 Why is HF the weakest acid among hydrohalo acids in spite of the fact that fluorine is most electronegative?Q.10 How would account for the following: 1.)Hydrogen fluoride is much less volatile than hydrogen chloride. 2.)Interhalogen compounds arestrong oxidising agents.Q.11 Xenon does not form fluorides such as XeF3 and XeF5.Give reasons.Q.12 Apply VSEPR theory to deduce the structures of XeF4 and XeF6.Q.13 Why are the interhalogen compounds more reactive than the related elemental halogens?Q.14 Account for the following: 1.)Deep sea divers use a mixture of He(80%) and O2(20%) instead of air for breathing. 2.)Sulphur exhibits greater tendency for catination than Se.Q.15 Give reasons for the following:- 1.)Addition of Cl2 to KI sol. gives it a brown colour, but excess of Cl2 turns it colourless. 2.)Phosphinic acid behaves as a monoprotic acid.

The d & f-block ElementsQ.1 In the transition series, with an increase in atomic no. The atomic radius does not change very much. Why?

Chemistry (Class XII) Q.2 State a consequence of lanthanoid contraction shown by transition group elements?Q.3 Which is the most stable oxidation state among lanthanoids?Q.4 State the common characteristics of actinoids and lanthanoids which place them in the f-block of elements?Q.5 Why is that orange sol. Of K2Cr2O7 turns yellow on adding NaOH to it?Q.6 What are the two important oxidation states of group 6 elements of the periodic table?Q.7 Write any two uses of phosphoric alloys?Q.8Why is HCl not used to acidify a permanganate sol. In volumetric estimations of Fe2+ or C2O42- ?Q.9 Why is K2Cr2O7 generally preferred over Na2Cr2O7 in volumetric analysis although both are oxidising agents?Q.10 Why is electronic configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d10 not correct for ground state of Cr(24)?Q.11 Why are complex ions readily formed when water molecules react with cations but not with hydronium ions?Q.12 What is meant by disproportionation reaction?Give an example.Q.13 Explain the following statements- 1.)The transition metals are well known for the formation of interstitial compounds? 2.)Why do actinoids in general,exhibit a greater range of oxidation states than the lanthanoids?Q.14 Write chemical equations for the reactions involved in the manufacture of potassium permanganate from pyrolucite ore.Q.15 What is misch metal? Mention its two important uses.Q.16 Explain the following statements- 1.)It is difficult to separate lanthanoid elements in pure state. 2.)The transition elements form interstitial compounds.Q.17 Give reasons- 1.)Size of trivalent lanthanoid cations decreases with increase in the atomic no. 2.)Chemistry of all lanthanoids is quite similar.Q.18 Transition metal fluorides are ionic in nature, whereas bromides and chlorides are covalent in nature.Explain.Q.19 Write balanced ionic equations for what happens when- 1.)Acidified potassium permanganate sol. Is treated with an oxalate ion in sol. 2.)An iodide ion is treated with an acidified dichromate ion in sol.Q.20 A serious accident occurred in the chemistry laboratory when a student tried to dissolve KMnO4 in conc. H2SO4 instead of dil. H2SO4. Explain why?