A quantity of 80.0 g of a salt (XY) of strong acid and weak base is dissolved in water to form 2.0 L aqueous solution. At 298 K, pH of the solution is found to be 5.0. If XY forms CsCl type crystal an

Question

A quantity of 80.0 g of a salt (XY) of strong acid and weak base is dissolved in water to form 2.0 L aqueous solution. At 298 K, pH of the solution is found to be 5.0. If XY forms CsCl type crystal and the radius of X+ and Y- ions are 160 pm and 186.4 pm, respectively, then the correct information is: (Given: Kb of XOH = 4 x 10^-5, Na = 6 x 10^23)

Prashant Kotian · Accepted Answer

Correct answer: A,B,C,D. Molar mass = 100 g/mol => C = 80/100 / 2 = 0.4 M. Kh = Kw/Kb = 10^-14 / 4e-5 = 2.5e-10. h = sqrt(Kh/C) = sqrt(2.5e-10 / 0.4) = 2.5e-5. [H+] = C*h = 1e-5 M => pH = 5.0. For CsCl: r+ + r- = a*sqrt(3)/2 => 160 + 186.4 = 346.4 pm = a*sqrt(3)/2 => a = 400 pm. density = Z*M / (Na*a^3) = (1 * 100) / (6e23 * (4e-8)^3) = 2.6 g/cm3.

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