An unlabeled bottle contains an unknown potassium halide salt, KX. A student mus

Question

An unlabeled bottle contains an unknown potassium halide salt, KX. A student must determine the identity of the salt be using freezing point depression data. Because KX is a strong elextrolyte, one mole of KX yields two moles of ions in solution. The student finds that when 1.13 g of the unknown salt is dissolved in 24.65 g of distilled water, the freezing point of the resulting solution is -1.01 degrees celcius. The freezing point of hte distilled water is determined to be +0.02 degrees celcius.

a). calculate the freezing point depression for the solution

b). calculate the molality of the solution

c). calculate the molar mass of the unknown salt

d). given that the salt is a potassium halide, KX, identify X, the halide ion.  

please explain, well! thanks!

Explanation / Answer

a)dT = (0.02-(-1.01) = 1.03

b) dT = i x kf x m

1.03 = 2 x 1.86 x m

m = 0.27688

c) m= 0.27688 = ( 1.13/molar mass) x ( 1000/24.65)

molar mas = 165.56

d) X = 165.56-K = 165.56-39.09 = 126.47 X = iodine

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