The solubility for PbCl2 is determined experimentally at different temperatures

Question

The solubility for PbCl2 is determined experimentally at different temperatures for through a titration of the aqueous chloride ion and the data is used to calculate Ksp Temperature of saturated of PbCl2 350.2 K 337.8 K 323.1 K 298.0 Ksp for PbCl2 5.16 x 10-3 3.33 x 10-3 1.81 x 10-3 6.31 x 1 Set the following two equations equal to each other and rearrange. What can be plotted as y versus x to provide a linear relationship? AGO AHO-TAS RT ln K a. Ksp versus T b. 1/Ksp versus ln T c. In Ksp versus T ln Ksp versus 1/T Using the graph paper supplied at the end of the exam, determine the value of the AH n from the data given above problem #31 Choose the closest answer! a. 36.4 kJ b. 125 kJ c. 2.07 kJ d. 0.055 kJ

Explanation / Answer

For a linear plot

we require

dG = dH - T*dS

AND

dG = -RT*ln(K)

If we want to relate how T increases with respect to Ksp, there is clearly an inverse relationship:

ln(K) vs 1/T

this will give us a slope of a striaght line

Q2

find dHRxn

ln(K) = -dH/(RT) + dS/R

clearly, the slope is -dH/R

so from previous data:

ln(K2) - ln(k1) / (1/T2 -1/T2) = m = -dH/R

(ln(1.81*10^-3) - ln(5.16*10^-3)) /(1/(323.1) - 1/(350.2)) = -4,374.04

dH = -8.314*-4374.04 = 36,365.768 J = 36.3 kJ is the answer

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