. The volumes of different solutions of aqueous copper (II) sulfate were measure
ID: 1040140 • Letter: #
Question
. The volumes of different solutions of aqueous copper (II) sulfate were measured as a function of the amount of CuSO4 added to 100.0 g of water. The results are given below. a) Find an expression for the partial molar volume of CuSO4 in terms of moles of CuSO4 (Hint: first, fit the data to a second order polynomial). b) From the expression found in (a), determine the partial molar volume of CuSO4 for a solution with 0.10 moles of CuSO4 added. Moles CuSO4 0.0300 0.0696 0.1106 0.1566 Solution volume/cm3 100.16 100.37 100.81 101.63
Explanation / Answer
'mole fraction of CuSO4= moles of CuSO4/ total moles
moles of CuSO4 data need to be converted to mole fraction of CuSO4.
moles of water= mass of water/18= 100/18= 5.55
total moles = moles of water+ moles of CuSO4
The data on moles of CuSO4 need to be converted to mole fraction of CuSO4.
from the plot, V= 2542x2-16,93x+0.001, dV/dx= 2*2452x-16.93
V1- = partial molar volume of CuSO4= V+x2*dV/dx1, where x2= mole fraction of water
given mole of CuSO4= 0.1, mole fraction of CuSO4=0.1/(0.1+5.55)= 0.01768, x2=1-x1=1-0.01768= 0.98232
dV/dx= 2*2542*0.01768-16.93=72.96
hence at x=0.01766, V=2542*(0.01766)2-16.93*0.01766+0.001=100.595
V1- = 100.595+0.98232*72.96=172.3 cm3.
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