solubility

factors that affect solubility

Certain factors can change the solubility of a solute. Temperature is one such factor. How temperature affects solubility depends on the state of the solute, as you can see in the Figure 1.1. If a solute is a solid or liquid, increasing the temperature increases its solubility. For example, more sugar can dissolve in hot water than in cold water. If a solute is a gas, increasing the temperature decreases its solubility. For example, less carbon dioxide can dissolve in warm water than in cold water. The solubility of gases is also affected by pressure. Pressure is the force pushing against a given area. Increasing the pressure on a gas increases its solubility. Did you ever open a can of soda and notice how it fizzes out of the can? Soda contains dissolved carbon dioxide. Opening the can reduces the pressure on the gas in solution, so it is less soluble. As a result, some of the carbon dioxide comes out of solution and rushes into the air. Q: Which do you think will fizz more when you open it, a can of warm soda or a can of cold soda? A: A can of warm soda will fizz more because increasing the temperature decreases the solubility of a gas. Therefore, less carbon dioxide can remain dissolved in warm soda than in cold soda.

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what is solubility

Solubility is the amount of solute that can dissolve in a given amount of solvent at a given temperature. In a solution, the solute is the substance that dissolves, and the solvent is the substance that does the dissolving. For a given solvent, some solutes have greater solubility than others. For example, sugar is much more soluble in water than is salt. But even sugar has an upper limit on how much can dissolve. In a half liter of 20 C water, the maximum amount is 1000 grams. If you add more sugar than this, the extra sugar wont dissolve. You can compare the solubility of sugar, salt, and some other solutes in the Table 1.1. Solute Baking Soda Epsom salt Table salt Table sugar Grams of Solute that Will Dissolve in 0.5 L of Water (20 C) 48 125 180 1000 Q: How much salt do you think Rhonda added to the half-liter of water in her experiment? A: The solubility of salt is 180 grams per half liter of water at 20 C. If Rhonda had added less than 180 grams of salt to the half-liter of water, then all of it would have dissolved. Because some of the salt did not dissolve, she must have added more than 180 grams of salt to the water.

instructional diagrams

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questions

for a given solvent, all solutes have the same solubility.

a. true

-->  b. false

less sugar can dissolve in cold water than in hot water.

-->  a. true

b. false

less carbon dioxide can dissolve in cold water than in hot water.

a. true

-->  b. false

increasing the pressure on a gas increases its solubility.

-->  a. true

b. false

which of the following substances is least soluble in water?

a) table salt

b) table sugar

-->  c) baking soda

d) epsom salt

the solubility of a gaseous solute depends on

a) its temperature.

b) the pressure on it.

c) the solvent.

-->  d) all of the above

you could increase the solubility of sugar in water by

a) putting the water under greater pressure.

-->  b) heating the water.

c) stirring the water.

d) all of the above

diagram questions

No diagram questions associated with this lesson