…no writing! heat capacities are for 298. 15K. 9. A liquid mixture consists of 3
ID: 3307455 • Letter: #
Question
…no writing!
heat capacities are for 298. 15K. 9. A liquid mixture consists of 33 gof component A and 99 of component B. Answer the following questions, using the accompanying figure. (a) At what temperature would the mixture begin to boil? (b) What is thecomposition of thevapor when,bilingfirstoccur (e) If the distillation is continued until the boiling point is raised by 2 °C, what would be tion of the liquid left in the still? YA (d) If fractional distillation is used in the experiment and the efficieney of the fractionating column is 100%, under the conditions in (c), whatare the composition and mass of the two components collected over the initial 2 °C interval? (20%) 90 O 70 50 30 wt %BExplanation / Answer
Before I provide the answer I wish reader to go through a small note from which the problem evolves.
Gibb's phase rule :
The number of degrees of freedom in a closed physical system at equilibrium is equal to the number of chemical components minus the number of phases plus the constant 2. Mathematically denoted by the equality,
F = C - P + 2
where F is the degrees of freedom, C is the number of components and P is the number of phases that are in thermodynamic equilibrium with each other.
9. Answer :
(a) Weight percentage is along X axis and amount of heat / ° C is along Y axis.
Wt % of B = {99 /(33+99)} x 100 = 75%
From the curve it is seen that the the first vapour appears at 60°C .
(b) The ends of the tie lines (the fade horizontal and vertical lines) show the compositions of the two phases ()the two liquids) that exist in equilibrium with each other at this temperature. In this case, the vapour contains 88 % B, as middle vertical line (tie line) intersects the curve at 0.8 .
(c) If the process is continued until the boiling point is raised by 2°C. The tie lines cut the curve at 62°C where vertical line shows the amount of 53% of B is present in the liquid.
(d) Fractional distillation is used to separate two nearly volatile substances. Composition and mass of the two substances collected over first 2°C are,
Total amount in fractional sample = (33+ 99 )g = 132g
Half of the amount of B = 88/2g = 44g
Therefore amount of B = {(132+ 44)}/ 132 g = 1.37g
% of B =1.37g x 100= 137
Therefore amount present in the liquid is 137-100=37 %
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