chemical engineering. Do number 2 Name: CHEN 3080 Materials Science and Engineer

Question

chemical engineering.
Do number 2

Name: CHEN 3080 Materials Science and Engineering: Fall 2017 Home Work 14 due Tue, Oct 31 Read 8.1, 8.2, 8.3, 8.4, 8.5, 8.7 Review Solved Problems: 8.2, 8.4, 8.5, 8.6 1. Consider the sugar-water phase diagram. what wt% sugar can you dissolve in water at room temperature ? what wt% sugar can you dissolve in water at 100°C? a. b, 2. If 60 gms of water and 140 gms of sugar are mixed and stirred at a temperature of 80°C a. Will this result in a single phase solution or a mixture? b. What will happen if the solution/mixture in part a. is slowly cooled to room temperature ? 3. (minus) Explain what happens when a 23wt% salt solution is cooled from room temperature to 30°C. Give information regarding the phases present, amounts of these phases and compositions of phases at-(minus) 30°C . 4. Based on the phase diagram, explain why city workers throw rock salt on icy roads ? Based on the phase diagram suggest a process that would produce almost pure water from seawater (3wt% salt). (You are not allowed to boil the water). 100 20 Liquid (salt water) Liquid (salt water) 60 Liquid (salt water) 10 Salt Liquid Liquid 40 Crystal 20 20 Ice (solid)+ Salt (solid) Salt 0% water 100% 10 90 100 15 20 Sugar 0 water 100% 80 80 20 20 75 70

Explanation / Answer

Q2

m = 60 g of water + 140 g of sugar

Solubility = 350 g of sugar per 100 g of water = 350/100 = 3.5 g/g

then

140/60 = 2.33 g/g

this is unsaturated

there is only one phase, aqueous solution

b)

if the solution is colled down to T = 25°C

S = 200 g/ 100 g --> 2 g /g approx

note that concentration is = 2.33 g/g

therefore, there will be cyrstallization, since it becomes uspersaturated solution

expect sucrose crystals to form

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