Dear Student, ∆Tf= iKf mSo, m=∆TfiKf∆Tf=Tf°-Tf=0-(-0 62)=0 62°CFor rock salt type crystal, i= 1+α=1+0 60=1 6So, m=0 621 6×1 86=0 2Effective molality of solution = 0 2Now Density=MassVolumeSo, Mass of water=Density×Volume=1 g/cm3×1000 cm3=1000 gHence, number of moles of ionic solid in given cube =Molality×Mass of water1000=0 2×10001000=0 2So, number of formula units in a given cube =0 2×6×1023Number of unit cells=14×0 2×6×1023=3×1022Number of units cells along one edge of cube =3×10223=3×107Edge length of unit cell, a=15×10-33×107=5×10-10 m=500×10-12m =500 pmHence, correct answer is (D)

solve 4 question
solve 4 question 1 rus of arrangement is not possible with the given radius ratio. A solid cubic crystal of edge length 15 mm of an ionic compound which has the rock salt type lattice, is added to 1 L of water (density 1 g cc) The freezing point of the solution found to be — 0.620C and degree of ionization of ionic compound is 60%(Given Kr of H20 = 1.86 kg/mol, 6 x 1023) 3. The correct figure given below, shows the location of anion ( type lattice BO in crystallographic face-diagonal plane corresponding the above unit cell is: 4. (C) Edge length of unit cell is (A) 300 pm (C) 600 pm (B) (B) 540 pm (D) 500 prn

Dear Student,

∆ T_{f} = {iK}_{f} . m So, m = \frac{∆ T_{f}}{{iK}_{f}} ∆ T_{f} = T_{f} ° - T_{f} = 0 - (- 0.62) = 0.62 ° C For rock salt type crystal, i = 1 + α = 1 + 0.60 = 1.6 So, m = \frac{0.62}{1.6 \times 1.86} = 0.2 Effective molality of solution = 0.2 Now . Density = \frac{Mass}{Volume} So, Mass of water = Density \times Volume = 1 g / {cm}^{3} \times 1000 {cm}^{3} = 1000 g Hence, number of moles of ionic solid in given cube = \frac{Molality \times Mass of water}{1000} = \frac{0.2 \times 1000}{1000} = 0.2 So, number of formula units in a given cube = 0.2 \times 6 \times 10^{23} Number of unit cells = \frac{1}{4} \times 0.2 \times 6 \times 10^{23} = 3 \times 10^{22} Number of units cells along one edge of cube = \sqrt[3]{3 \times 10^{22}} = 3 \times 10^{7} Edge length of unit cell, a = \frac{15 \times 10^{- 3}}{3 \times 10^{7}} = 5 \times 10^{- 10} m = 500 \times 10^{- 12} m = 500 pm Hence, correct answer is (D)

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