Pre-Lab Calculations 1. Calculate how much 95% ethyl alcohol will be required to

Question

Pre-Lab Calculations 1. Calculate how much 95% ethyl alcohol will be required to dissolve 0.3 g of sulfa- nilamide at 78°C. Use the data for the graph in Technique 11, Figure 11.2 to make this calculation. The reason for making this calculation is so that you wil know ahead of time the approximate amount of hot solvent you will be adding. 2. Using the volume of solvent calculated in Step 1, calculate how much sulfanilamide will remain dissolved in the mother liquor after the mixture is cooled to 0°C.

Explanation / Answer

The first thing to do is to make an interpolation (or stimation) for the solubility at 78 C, since this temperature is very close to 80C then we can expect to have a very similar solubility, lets put the values (descending order)

1. 80...............210

2. 70.................x

3. 60................88

for each side apply the next equation

(x1- x2) / (x1-x3) = (y1-y2)/(y1-y3)

(80 - 70) / (80 - 60) = (210 - x) / (210 - 88)

0.1 = 210 - x / (122)

12.2 = 210 - x

x = 210 - 12.2 = 197.8 g/ml

lets use the value of 198 g/ml for solubility

(You can use another stimation technique like guessing but be careful , the result must be consistent with the original data)

In 1 ml at this temperature you can put 198 miligrams of solute we want to solve only 0.3 grams

0.3 grams * 1000 = 300 miligrams

in 1 ml you can put 198 miligrams

in 2 ml you can punt 396 miligrams

The required volume must be between these last 2 values to find i

make a division

300mg / 198 (mg/ml) = 1.51 mililiters

you will need 1.51 militer of ethanol

B)

If you cool the mixture to 0C the solubility will be 14 mg/ml so

in 1.51 mililiter (just multiply

14 mg/ml * 1.51 ml = 21.14 mg

only 21.14 mg will remain dissolved in the solution the rest

300 - 21.14= 278.86 miligrams will not dissolve

*if this answer is helpful dont forget to rate it =)

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