MODEL PAPER CBSE 2018 PHYSICAL CHEMISTRY

                                      PHYSICAL CHEMISTRY XII-2018

Q1. In summer, a given sample of milk turns sour at 27°C in 48 hours. In a 2 refrigerator at 2°C, milk can be stored three times longer before it sours. Calculate the activation energy of the souring of milk. R=8.31 JK–1 mol–1 16. Find the Gibbs energy change of the cell at 298K.

3 Cr |Cr³⁺ (0.1M)       ||          Cu2+(0.01M) ⁺ |Cu.

 Given E° Cr³⁺ / Cr = – 0.75V, Cu²⁺/Cu = +0.34V, F = 96500C.

Q2. Differentiate between the following

(a) Multimolecular colloids and macromolecular colloids

(b) Coagulation and peptisation

c) Activity and selectivity of catalyst

Q3.Analysis shows that a metal oxide has the empirical formula M _0.96 O _1.00. Calculate the percentage of M²⁺ and M³⁺ ions in this crystal?

Q4.In an ionic compound the anion (N¯ ) form cubic close type of packing. While the cation (M+ ) ions occupy one third of the tetrahedral voids. Deduce the empirical formula of the compound and the coordination number

Q5.Heptance and octane form an ideal solution at 373 K, The vapour pressures of the pure liquids at this terperature are 105.2 KPa and 46.8 KPa respectively. If the solution contains 25g of heptance and 28.5g of octane, calculate (i) vapour pressure exerted by heptane (ii) vapour pressure exerted by solution (iii) mole fraction of octane in the vapour phase.

 Q6. The following chemical reaction is occurring in an electrochemical cell.

 Mg(s) + 2 Ag⁺ (0.0001 M)---à Mg²⁺ (0.10M) + 2 Ag(s)

The electrode values are    Mg2+ / Mg = – 2. 36 V                      Ag+ / Ag = 0.81 V

 For this cell calculate / write

 (a)      (i) EMF value for the electrode 2Ag+ / 2Ag

            (ii) Standard cell potential EMF cell.

 (b) Cell potential (E)cell

 (c)       (i) Symbolic representation of the above cell.

            (ii) Will the above cell reaction be spontaneous?

 Q7. Consider the adsorption isotherms given below and interpret the variation in the extent of adsorption (x/m) when (7) (a) (i) temperature increases at constant pressure (ii) pressure increases at constant temperature (b) Name the catalyst and the promoter used in Haber’s process for manufacture of ammonia.

Q8. For a certain chemical reaction variation in the concentration in [R] vs. time (s) plot is given below. For this reaction write / draw (i) what is the order of the reactions? (ii) what are the units of rate constant k? (iii) give the relationship between k and t ½ (half life period) (iv) what does the slope of the above line indicate? (v) draw the plot log [R]0 / [R] vs time t(s)

Q9. For a certain chemical reaction

             A        +          2B      -------à2C      +          D

The experimentally obtained information is tabulated below.

Experiment                [A]0                             [B]0                             Initial rate of reaction

1 0.                              0.30                            0.30                                        0.096

2                                  0.60                           0.30                                       0.384

3                                  0.30                            0.60                                        0.192

 4                                 0.60                            0.60                                        0.768

For this reaction (i) derive the order of reaction w.r.t. both the reactants A and B. (ii) write the rate law. (iii) calculate the value of rate constant k (iv) write the expression for the rate of reaction in terms of A and C.

Q10.The radius of a calcium ion is 94 pm and of an oxide ion is 146 pm. Predict the crystal structure of calcium oxide.

Q11.The unit cell of silver iodide (AgI) has 4 iodine atoms in it. How many silver atoms must be there in the unit cell.

Q12.In the close packed cation in an AB type solid have a radius of 75 pm, what would be the maximum and minimum sizes of the anions filling the voids?

Q13.The density of CaO is 3.35 gm/cm³. The oxide crystallises in one of the cubic systems with an edge length of 4.80 Å. How many Ca⁺⁺ ions and O^–2 ions belong to each unit cell, and which type of cubic system is present?

Q14.If NaCl is doped with 10^-3 mole% SrCl₂ what is the concentration of cation vacancies?

Arginine vasopressin is a pituitary hormone. It helps to regulate the amount of water in the body by reducing the flow of urine form kidneys. An aqueous solution containing 21.6 mg of vasopressin in 100 mL of solution had an osmotic pressure of 3.70 mm Hg at 25^oC. What is molecular weight of hormone?

Q15.Calculate osmotic pressure of 5% solution of cane sugar (sucrose) at 15^oC. 

Q16.A solution of 2.5 g of a non-volatile solid in 100 g benzene boiled at 0.42^oC higher than the boiling point of pure benzene. Calculate the molecular mass of the substance. Molal elevation constant of benzene is 2.67 K kg mol⁻¹.

Q17.For a first order reaction when log k was plotted against , a straight 1/T line with a slope of -6000 was obtained. Calculate the activation energy of the reaction 

Q18.For a reaction, the energy of activation is zero. What is the value of rate constant at 300 K if k = 1.6   106 s^–1 at 280 K? (R = 8.31 J K^–1 mol^–1)

Q19.The time required for 10% completion of first order reaction at 298 K is equal to that required for its 25% completion at 308K. If the preexponential factor for the reaction is 3.56 ´ 10⁹ s^–1, calculate the energy of activation

Q20.How much electric charge is required to oxidise (a) 1 mole of H₂O to O₂ and  (b)1 mole of FeO to Fe₂O₃? 

Q21.A 100 watt, 100 volt incandescent lamp is connected in series with an  electrolytic cell containing cadmium sulphate solution. What mass of cadmium will be deposited by the current flowing for 10 hours? 

Q22.A current of 2.68 ampere is passed for one hour through an aqueous solution of copper sulphate using copper electrodes. Calculate the change in mass of cathode and that of the anode. (At. mass of copper = 63.5).