8.2 Solubility and Concentration. Solubility The maximum amount of a solute that dissolves in a given amount of solvent at a constant temperature is called.

Chapter 88.2 Solubility and Concentration

Solubility The maximum amount of a solute that

dissolves in a given amount of solvent at a constant temperature is called solubility.

Solubility Solubility is given as grams of solute per 100

grams of solvent at a specific temperature.Example:The solubility of table salt or sodium chloride

is 36.0.That means that 36.0 grams of sodium

chloride will dissolve in 100 grams of water at 20 degrees Celsius.

Types of Solutions Depending on the amount of solute in

solution, solutions can be:SaturatedUnsaturatedSupersaturated

Saturated SolutionsA saturated solution contains as much solute

as the solvent can hold at a given temperature.

If you add more solute to a saturated solution, it will NOT dissolve.

Unsaturated SolutionsUnsaturated solutions have less than the

maximum amount of solute that can be dissolved in the solvent.

Supersaturated SolutionsSupersaturated solutions contain more solute

than they can normally hold at a given temperature.

These are very unstable.The solvent must be heated above normal

temperature to make the extra solute dissolve and then carefully cooled.

Solutions The solubility of sugar in water is 203.9

grams at 20 degrees Celsius. If 50 grams of sugar are dissolved in water,

what type of solution is it?What if 203.9 grams of sugar are dissolved?What if 210 grams of sugar are dissolved?

Solutions AnswersUnsaturatedSaturatedSupersaturated

What Affects Solubility?Solubility is affected by:The polarity of the solventTemperaturePressure

Polar and Nonpolar SolventsSolvent Type Solute Type Will Solution Form?

Polar Polar (or ionic) More likely

Polar Nonpolar Not likely

Nonpolar Polar (or ionic) Not likely

Nonpolar Nonpolar More likely

Temperature For solid solutes, solubility increases as

temperature increases.For gas solutes, solubility decreases as

temperature increases.

Pressure For gas solutes, solubility increases as

pressure increases.

Concentration of Solutions Concentration can be expressed as percent

by volume, percent by mass, and molarity.

Concentration Percent by volume = volume of solute ÷

volume of solution x 100%Example:If a 200 mL drink contains 50 mL of solute,

what is its concentration in percent by volume?

50/200x100=25% soluteThis is what is meant when a drink says that

it is a certain percent fruit juice by volume.

Percent by VolumeA 200mL drink is 27% fruit juice by volume.

What volume of fruit juice does it contain in milliliters?

Fruit juice/200x100=27Fruit juice/200=27/100Fruit juice=(27/100)x200Fruit juice =54 mL

Concentration Percent by mass = mass of solute ÷ mass of

solution x 100%Example:In 100 grams of solution there are 20 grams

of solute. What is the concentration in percent by mass?

20/100x100=20%

Percent by MassA 200 g solution is allowed to evaporate.

After the solvent is gone, 20 grams of solute remain. What was the solution’s concentration in percent by mass?

20/200x100=10%

Concentration Molarity = moles of solute/liters of solution Molarity is the number of moles of a solute

dissolved per liter of solution.

Molarity To make a 1-molar (1 M) solution of sodium

chloride in water:Calculate the molar mass of the solute.NaCl has a molar mass of 58.5 grams.If 58.5 grams of NaCl is mixed with enough

water to make 1 liter of solution, the resulting solution is 1-molar.

Molarity How would you make a 1 M solution of table

sugar (C12H22O11)?Find the molar mass of table sugar.12x12.011+22x1.0079+11x15.999= 144.132+22.1738+175.989=342.295g/molAdd enough water to 342 grams of table

sugar to make 1 liter of solution.