6/22/2017 B
Solutions
Chemistry 110
1) Solubility
020 40 60 80 100
0
10
20
30
40
50
60
70
Temperature •C
g K2Cr2O7 / 100g H2O
Solubility curve for potassium dichromate
Using the above solubility curve answer the following questions:
a] What is the solubility of K2Cr2O7 at 55 oC? approximately __36_g/100 ml
b] What is the maximum number grams of K2Cr2O7 that will dissolve in 35 grams of water at 30oC? 35g
H2O X 14g K2CrO7
100g H2O = 4.9 g approximately ___4.9 g____
c] If K2Cr2O7 does not supersaturate, tell how many grams will precipitate out per 100 g of solvent when a solution
containing 30 g per 100 g of water at 60oC is cooled to 20oC (30-8)g = __22g__
d] For each of the following, indicate what kind of solution exists.......
(a) saturated, (b) unsaturated
-If the solution contains 2 g K2Cr2O7 in 10 g water at 40oC _____b_____
-If the solution contains 20 grams in 50 g water at 60oC _____a_____
-If the solution contains 90 g in 300 g water at 70 oC _____b_____
2] A 0.200 g sample of tissue from a dead bald eagle is found to contain 2.42 µg of DDT. Express this DDT
concentration as mass percent.
2.42 x 10-6g
0.200g sample (100) = 1.21 x 10-3 %
__________________________
3] How would you prepare 250.0 g of a 1.00% by mass of a silver nitrate solution?
250.0g soln X 1.00g AgNO3
100g soln = 2.50 g AgNO3
Answer: Mix ___2.50___g of silver nitrate with ___247.5__g of water
4] How many milliters of solution are required to provide 4.00 g sodium acetate from a 2.00 M sodium acetate
solution?
4.00g Na2C2H3O2 X 1mol Na2C2H3O2
82.0g Na2C2H3O2 X
1L soln
2.00mol Na2C2H3O2 X 1ml
10-3L = 24.4ml soln
