Kg solvent Delta G = Delta H - T Delta S E = hv h = 6.626 times 10^-34 J lambda
ID: 527215 • Letter: K
Question
Kg solvent Delta G = Delta H - T Delta S E = hv h = 6.626 times 10^-34 J lambda = cv c = 2.998 times 10 m/s R_H = 2.18 times 10^-18 J Delta E = R_H(1/n^2_1 - 1/n^2_1) [H^+][OH^-] = 1.0 times 10^-24 PH = -log[H^+] [H^+] = 10^-PH PH = pk_a + log ([conj. base]/[conj. Acid]) The freezing point depression of an aqueous solution of an ionic solute is 2.77 degree C in 8 165 g of water. The solution was made by dissolving 0.747 g of a compound with a formula weight of 126 96 g/mol. What is the van't Hoff factor, , of the substance in the solution? The freezing point depression constant, K_f, for water is 1.86 degree C/m. A. 173 B. 0.484 C 3.71 D. 2.07 When a certain amount of NH_4NO_3 is dissolved in water at 25 degree C, the temperature of the solution was 12 degree C. from this information, we know the following: A. Delta W is positive; Delta S is negative. B. Delta H is negative; Delta S is negative. C. Delta H is positive; Delta S cannot be determined. D. Delta H is positive; Delta S is positive. The equilibrium constant, K_c of the following reaction is measured: Fe^3+(aq) + SCN^-(aq) [Fe(NCS)]^2 + (aq) The initial concentration of Fe^3+ is 4.00 times 10^-4 M. The initial concentration of SCN is 1.00 times 10^-3 M. Use equilibrium concentration of Fe[NCS]^2+ was determined by calorimetry to be 7.35 times 10^-5 M. What is the equilibrium constant? A. 5.44 times 10^-1 B. 184 C. 2.09 times 10^-4 D. 243 In the equilibrium in question 3, the reactants are colorless or neatly so, but the product is a deep red. What can be done to cause the red color to be deeper (greater concentration of product)? A. Increase the concentration of SCN^-. B. Add Ag^+, which forms a precipitate with SCN^-. C. Dilute the equilibrium mixture. D. Add PO_4^3-, which forms a precipitate with Fe^3+. The pK_a of NH_4^+ is 9.26. If 20.0 mL of a 0.100 M solution of NH_4Cl is mixed with 25.0 mL of a 0. 0400 M solution of NaOH, what will be the pH of the resulting mixture? A. 3.05 B. 9.26 C. 5.31 D. 4.74Explanation / Answer
Ans 1. D . 2.07
Delta Tf = i. kf. m
where i is the vant hoff's factor
m is the molality of the solution , which is given as ( w2 / M2) / ( w1 x 1000)
where w2 and M2 is the mass of solute and molar of solute respectively
w1 is the mass of solvent
putting all the terms in the formula above
2.77 = (i x 1.86 x 0.747 x 1000 ) / 126.96 x 8.165
i = 2.07
So the vant hoff's factor is 2.07.
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