Identifying an Unknown Compound Flowchart
Solubility in Water Generalizations
Solids
-Solids usually have ________________ solubility in water at _______________
temperatures.
-For example, lithium bromide has a solubility of 143 g/100 mL at 0oC, and a
solubility of 266 g/100 ml at 100oC
Gases
-Gases always have _________________solubility in water at lower
temperatures.
-The solubility of gas ________________ as the temperature increases.
-Gases always have _________________solubility in water at _______________
pressures.
Liquids
-It is difficult to generalize about the effect on the solubility of liquids in water.
-For polar liquids in water, the solubility usually increases with temperature
-Some liquids (mostly non-polar liquids) do not dissolve in water but form a
separate layer. Liquids that behave this way are said to be ________________
with water.
-Some liquids (mostly small polar molecules with hydrogen bonding) dissolve
completely in water in any proportion. These liquids are said to be
________________ with water.
Elements
-Elements generally have very ______________ solubility in water.
Assignment: Investigating the Relationship
between Solubility and Temperature
For this assignment we will look at the solubility of two different chemicals
at various temperatures to evaluate the accuracy of our generalizations. We will
construct a graph that compares the solubility of potassium nitrate in water with the
solubility of hydrogen chloride in water. Make sure to read the whole assignment
first so that you can properly label the axes on your graph. Include a legend on
your graph to distinguish one data set from the other.
Part A: Solubility of potassium nitrate
Read Lab Exercise 5.C on page 223. Next, on a sheet of graph paper construct a
graph showing the relationship between the solubility of potassium nitrate and the
temperature of the solution. Construct a best-fit line for the data.
Part B: Solubility of hydrogen chloride
Another experiment determined the solubility of hydrogen chloride in water
by bubbling a known volume of hydrogen chloride through the water until it
became saturated, then measuring the volume of hydrogen chloride remaining.
This difference in volume was then used to calculate the mass of hydrogen chloride
that was dissolved in the water. The experiment was repeated at various
temperatures, while the pressure remained constant.
Table 2: Solubility of hydrogen chloride at various temperatures.
Temperature (oC)
Volume of solution (mL)
Mass of HCl(g) (grams)
10.0
100.0
75.1
20.0
100.0
70.0
30.0
100.0
65.5
40.0
100.0
61.0
50.0
100.0
57.5
On the same sheet of graph paper as you used in Part A, construct a graph showing
the relationship between the solubility of hydrogen chloride and the temperature of
the solution. Construct a best-fit line for the data.
Part C: Analysis and Evaluation
Answer the following questions on a separate sheet of paper.
1) Using the line of best fit on your potassium nitrate graph, predict the
solubility at the following temperatures:
a) 19oC
b) 70oC
2) Using the line of best fit on your hydrogen chloride graph, predict the
solubility at the following temperatures:
a) 27oC
b) 1oC
c) 85oC
3) Could we use the line of best fit to predict the solubility of a compound at
any given temperature? Why or why not?
4) Did the solubility and temperature relationships agree with what was
predicted by our generalizations?
5) The design of Lab Exercise 5.C (pg 233) describes the process used to find
the solubility of potassium nitrate. Could we use this method to determine
the solubility of any solid compound?
When you are finished, hand in this sheet along with your graph and the
answers to the above questions
Assignment: Investigating the Relationship between Solubility and Temperature
Graph sheet
Axes labelled correctly (w/units)
Legend
Accuracy of plotting
Best fit line
Legibility
/4
/2
/2
/1
/1
Analysis and Evaluation Questions
/10
Total
/20