<< Chapter < Page Chapter >> Page >

Solutions of solids in liquids

The dependence of solubility on temperature for a number of inorganic solids in water is shown by the solubility curves in [link] . Reviewing these data indicate a general trend of increasing solubility with temperature, although there are exceptions, as illustrated by the ionic compound cerium sulfate.

This shows a graph of the solubility of sugar C subscript 12 H subscript 22 O subscript 11, K N O subscript 3, N a N O subscript 3, N a B r, K B r, N a subscript 2 S O subscript 4, K C l, and C e subscript 2 left parenthesis S O subscript 4 right parenthesis subscript 3 in g solute per 100 g H subscript 2 O at temperatures ranging from 0 degrees Celsius to 100 degrees Celsius. At 0 degrees Celsius, solubilities are approximately 180 for sugar C subscript 12 H subscript 22 O subscript 11, 115 for K N O subscript 3, 75 for N a N O subscript 3, 115 for N a B r, 55 for K B r, 7 for N a subscript 2 S O subscript 4, 25 for K C l, and 20 for C e subscript 2 left parenthesis S O subscript 4 right parenthesis subscript 3. At 0 degrees Celsius, solubilities are approximately 180 for sugar C subscript 12 H subscript 22 O subscript 11, 115 for K N O subscript 3, 75 for N a N O subscript 3, 115 for N a B r, 55 for K B r, 7 for N a subscript 2 S O subscript 4, 25 for K C l, and 20 for C e subscript 2 left parenthesis S O subscript 4 right parenthesis subscript 3. At 100 degrees Celsius, sugar C subscript 12 H subscript 22 O subscript 11 has exceeded the upper limit of solubility indicated on the graph, 240 for K N O subscript 3, 178 for N a N O subscript 3, 123 for N a B r, 105 for K B r, 52 for N a subscript 2 S O subscript 4, 58 for K C l, and the graph for C e subscript 2 left parenthesis S O subscript 4 right parenthesis subscript 3 stops at about 92 degrees Celsius where the solubility is nearly zero. The graph for N a subscript 2 S O subscript 4 is shown in red. All others substances are shown in blue. The solubility of this substance increases until about 30 degrees Celsius and declines beyond that point with increasing temperature.
This graph shows how the solubility of several solids changes with temperature.

The temperature dependence of solubility can be exploited to prepare supersaturated solutions of certain compounds. A solution may be saturated with the compound at an elevated temperature (where the solute is more soluble) and subsequently cooled to a lower temperature without precipitating the solute. The resultant solution contains solute at a concentration greater than its equilibrium solubility at the lower temperature (i.e., it is supersaturated) and is relatively stable. Precipitation of the excess solute can be initiated by adding a seed crystal (see the video in the Link to Learning earlier in this module) or by mechanically agitating the solution. Some hand warmers, such as the one pictured in [link] , take advantage of this behavior.

Three photos of hand warmers are shown side by side with an arrow pointing from the first photo to the second, and another arrow pointing from the second photo to the third. The first packet contains a clear colorless liquid and a small metal disc can be seen. In the second packet, the disc can’t be seen and a dispersion of white liquid is beginning. In the third packet, all of the liquid is white.
This hand warmer produces heat when the sodium acetate in a supersaturated solution precipitates. Precipitation of the solute is initiated by a mechanical shockwave generated when the flexible metal disk within the solution is “clicked.” (credit: modification of work by “Velela”/Wikimedia Commons)

Key concepts and summary

The extent to which one substance will dissolve in another is determined by several factors, including the types and relative strengths of intermolecular attractive forces that may exist between the substances’ atoms, ions, or molecules. This tendency to dissolve is quantified as substance’s solubility, its maximum concentration in a solution at equilibrium under specified conditions. A saturated solution contains solute at a concentration equal to its solubility. A supersaturated solution is one in which a solute’s concentration exceeds its solubility—a nonequilibrium (unstable) condition that will result in solute precipitation when the solution is appropriately perturbed. Miscible liquids are soluble in all proportions, and immiscible liquids exhibit very low mutual solubility. Solubilities for gaseous solutes decrease with increasing temperature, while those for most, but not all, solid solutes increase with temperature. The concentration of a gaseous solute in a solution is proportional to the partial pressure of the gas to which the solution is exposed, a relation known as Henry’s law.

Key equations

  • C g = k P g

Chemistry end of chapter exercises

Suppose you are presented with a clear solution of sodium thiosulfate, Na 2 S 2 O 3 . How could you determine whether the solution is unsaturated, saturated, or supersaturated?

Got questions? Get instant answers now!

Supersaturated solutions of most solids in water are prepared by cooling saturated solutions. Supersaturated solutions of most gases in water are prepared by heating saturated solutions. Explain the reasons for the difference in the two procedures.

The solubility of solids usually decreases upon cooling a solution, while the solubility of gases usually decreases upon heating.

Got questions? Get instant answers now!

Suggest an explanation for the observations that ethanol, C 2 H 5 OH, is completely miscible with water and that ethanethiol, C 2 H 5 SH, is soluble only to the extent of 1.5 g per 100 mL of water.

Got questions? Get instant answers now!

Calculate the percent by mass of KBr in a saturated solution of KBr in water at 10 °C. See [link] for useful data, and report the computed percentage to one significant digit.

40%

Got questions? Get instant answers now!

Which of the following gases is expected to be most soluble in water? Explain your reasoning.

(a) CH 4

(b) CCl 4

(c) CHCl 3

Got questions? Get instant answers now!

At 0 °C and 1.00 atm, as much as 0.70 g of O 2 can dissolve in 1 L of water. At 0 °C and 4.00 atm, how many grams of O 2 dissolve in 1 L of water?

2.80 g

Got questions? Get instant answers now!

Refer to [link] .

(a) How did the concentration of dissolved CO 2 in the beverage change when the bottle was opened?

(b) What caused this change?

(c) Is the beverage unsaturated, saturated, or supersaturated with CO 2 ?

Got questions? Get instant answers now!

The Henry’s law constant for CO 2 is 3.4 × 10 −2 M /atm at 25 °C. What pressure of carbon dioxide is needed to maintain a CO 2 concentration of 0.10 M in a can of lemon-lime soda?

2.9 atm

Got questions? Get instant answers now!

The Henry’s law constant for O 2 is 1.3 × 10 −3 M /atm at 25 °C. What mass of oxygen would be dissolved in a 40-L aquarium at 25 °C, assuming an atmospheric pressure of 1.00 atm, and that the partial pressure of O 2 is 0.21 atm?

Got questions? Get instant answers now!

How many liters of HCl gas, measured at 30.0 °C and 745 torr, are required to prepare 1.25 L of a 3.20- M solution of hydrochloric acid?

102 L HCl

Got questions? Get instant answers now!

Questions & Answers

what is the oxidation number of this compound fecl2,fecl3,fe2o3
Asmau Reply
bonds formed in an endothermic reaction are weaker than the reactants but y r these compound stable at higher temperatures
zille Reply
what is a disproportionation reaction
Ogor Reply
name the force that exist in cao
folarin Reply
what is chemistry
Richard Reply
so from dis concept rust x an atom
quame Reply
compare the dual nature of light
Eddie Reply
light behaves as particle and as well as waves in some phenomena....
zille
list 10 gases and their IUPAC name
Ogweimoh Reply
what are the likely questions for jamb
richez Reply
in group atomic number?
Dolly Reply
why is contact process important?
Kolawole Reply
what structure?
Musa Reply
of the above question.
Nakyanzi
Draw the Lewis structure of the following : Nitrate anion Nitrogen dioxide
Nakyanzi Reply
a first order reaction is 40% complete after 8 minutes how long will it be before it is 95% complete
IKO Reply
plea what are the best topics in chemistry to know
Sandra Reply
atomic theory . nuclear chemistry . chemical reaction. chemical equilibrium . organic chemistry. molecules concept 1 n 2. kinetic theory of gases.
Inusah
wat topics are the most important in biology
Josephine
cells 1 n 2, ecology. insects. genetics. plants. nutrition.
Inusah
organic chemistry
Dolly
Practice Key Terms 8

Get the best Chemistry course in your pocket!





Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry' conversation and receive update notifications?

Ask