EKLAVYA EDUCATION

ELINGHAM     DIAGRAME    AND    ITS    APPLICATIONS;- Ellingham Diagram -Thermodynamics of Metallurgy 1 .Gibbs equation helps us to predict the spontaneity of a reaction on the basis of  enthalpy  and entropy values directly. 2. Ellingham proposed the Ellingham diagram to predict the spontaneity of reduction of various metal oxides. Ellingham diagram was basically a curve which related the Gibbs energy value with the temperature. Gibbs energy is given as:    ΔG = ΔH – TΔS Where ΔH is the change in enthalpy and ΔS is the change in entropy. With respect to a reaction, Gibbs energy can be related to the  equilibrium  constant as: ΔG o = – RTlnK Where K is the equilibrium constant. 3. when the reaction is exothermic, enthalpy of the system is negative, thus making Gibbs free energy negative. Hence, we can say that the reaction will proceed in the forward direction due to a positive value of the equilibrium constant. T

                                     CBSE  SAMPLE QUESTION PAPER                                             CLASS XII CHEMISTRY(043)   Time: 3 hrs                                                                                                    MM: 70 GENERAL INSTRUCTIONS:            1. All the questions are compulsory.            2. Q. No. 1 to 5 are very short answer type, carrying 1mark each.           3. Q. No. 6 to 10 are short answer type, carrying 2 marks each.           4. Q. No. 11 to 22 are short answer type, carrying 3 marks each.           5. Q.No.23 is a value based question carrying 4 marks.           6. Q. No. 24 to 26 are long answer type, carrying 5 marks each.           7. Use of calculators is not allowed, use log tables wherever required. Q1 . Name the non stoichiometric point defect responsible for colour in alkali metal halides. Q2 .What is shape selective catalysis? Q3 .Amongst the isomeric alkanes of molecular formula C5H12,

SOLUTION OF THE PAPER CBSE MODEL                                                                              (In brief) 111 Metal excess or anionic vacancies or F-centres 1 22 Catalysis by zeolites which depends on the shape and size of the reactants and the products as compared to those of the pores and cavitites of zeolites. 1 3 Neopentane or 2,2-Dimethylpropane 1 4 3-Chloropropanamine, CH 3 CH(Cl)CH 2 NH 2 ½, ½ 5 Three ions [Co(NH 3 ) 6 ] 2+ , 2Cl − 1 6 No, the elevation in boiling point is not the same. Elevation in boiling point is a colligative property which depends on the number of particles. NaCl is an ionic compound which dissociates in solution to give more number of particles whereas sugar is made up of molecules and thus does not dissociate. ½ 1½