Solutions and Solubility

What is a Solution? A solution is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent.

Solubility Guidelines Not all substances are soluble in water Reference Table F lists solubility rules and exceptions to those rules.

Soluble Not Soluble

Regents Question: 06/03 #14 According to Table F, which of these salts is least soluble in water? LiCl (2) RbCl (3) FeCl2 (4) PbCl2 þ

Regents Question: 08/02 #40 Which of the following compounds is least soluble in water? (1) copper (II) chloride (2) aluminum acetate (3) iron (III) hydroxide (4) potassium sulfate þ

The concentration of a solution may be expressed as molarity (M), percent by volume, percent by mass, or parts per million (ppm). (3.1pp) Molarity Percent by mass Parts per Million M = moles of solute % = grams solute x 100 ppm = grams solute x 1,000,000 Liters solution Grams solution Percent by volume % = liters solute x 100 Liters solution

Regents Question: 06/02 #42 What is the molarity of a solution that contains 0.50 mole of NaOH in 0.50 liter of solution? (1) 1.0 M (3) 0.25 M (2) 2.0 M (4) 0.50 M þ Molarity = Moles Liters

Regents Question: 08/02 #49 What is the total number of grams of NaI(s) needed to make 1.0 liter of a 0.010 M solution? (1) 0.015 (3) 1.5 (2) 0.15 (4) 15 þ Na 1 x 23.0 = 23.0 I 1 x 126.9 = 126.9 149.9 g / mole Molarity = moles liters 0.010M = x 1.0 L X = 0.010 moles 0.010 moles x 149.9 g/mole =

Regents Question: 08/02 #36 How many moles of solute are contained in 200 milliliters of a 1 M solution? (1) 1 (3) 0.8 (2) 0.2 (4) 200 þ

Solubility of a nonvolatile solute depends on temperature. Solubility is the maximum amount of solute that a solvent can hold at a given temperature. A saturated solution is one in which the solvent has as much solute as it can hold

An unsaturated solution is one in which the solvent can dissolve more solute A supersaturated solution is one in which there is more solute dissolved than a solvent can normally hold. Make a supersaturated solution by cooling a saturated solution Supersaturated solutions are unstable and will precipitate the excess solute when a seed crystal is added. As temperature increases, solubility of a solid increases

Table G shows the solubilities of some gases and some solids at various temperatures when dissolved in 100 grams of water.

A solution which is on the line is saturated A solution below the line is unsaturated A solution above the line and fully dissolved is supersaturated

Regents Question: 06/02 #40 According to Reference Table G, which solution is saturated at 30°C? (1) 12 grams of KClO3 in 100 grams of water (2) 12 grams of KClO3 in 200 grams of water (3) 30 grams of NaCl in 100 grams of water (4) 30 grams of NaCl in 200 grams of water þ

Add a test crystal to see if a solution is unsaturated, saturated or supersaturated. Unsaturated – the test crystal dissolves Saturated – the test crystal settles to the bottom Supersaturated – a large amount of crystals precipitate from the solution

The solubility of a gas depends on temperature and pressure. As temperature increases, the solubility of a gas decreases As pressure increases, the solubility of a gas increases

Which are gases?

Regents Question: 08/02 #48 One hundred grams of water is saturated with NH4Cl at 50°C. According to Table G, if the temperature is lowered to 10°C, what is the total amount of NH4Cl that will precipitate? (1) 5.0 g (3) 30. g (2) 17 g (4) 50. g þ

Regents Question: 01/03 #65-66 When cola, a type of soda pop, is manufactured, CO2 (g) is dissolved in it. A capped bottle of cola contains CO2 (g) under high pressure. When the cap is removed, how does pressure affect the solubility of the dissolved CO2 (g)? A glass of cold cola is left to stand 5 minutes at room temperature. How does temperature affect the solubility of the CO2 (g)? As the pressure decreases, the solubility decreases. As the temperature increases, the solubility decreases.

Oil and water are not miscible Like dissolves like (charged solutes dissolve in charged solvents, uncharged solutes dissolve in uncharged solvents) Nonpolar solutes dissolve in nonpolar solvents Polar solutes dissolve in polar solvents Ionic solutes dissolve in polar solvents (Nonpolar) (Polar) Dry cleaners use a nonpolar solvent to get rid of oil and grease Liquids that dissolve each other are called miscible liquids.

Regents Question: 06/03 #42 Hexane (C 6 H 14 ) and water do not form a solution. Which statement explains this phenomenon? (1) Hexane is polar and water is nonpolar. (2) Hexane is ionic and water is polar. (3) Hexane is nonpolar and water is polar. (4) Hexane is nonpolar and water is ionic. þ

Regents Question: 01/03 #40 Solubility data for four different salts in water at 60°C are shown in the table below. Which salt is most soluble at 60°C? (1) A (2) B (3) C (4) D Salt Solubility in Water at 60 °C A - 10 grams /50 grams H2O B - 20 grams /60 grams H2O C - 30 grams /120 grams H2O D - 40 grams/80 grams H2O þ

Hint: 200 g of water was used – table G is for 100 g of water Regents Question: 01/04 #56-58 A student uses 200 grams of water at a temperature of 60°C to prepare a saturated solution of potassium chloride, KCl. Identify the solute in this solution. According to Reference Table G, how many grams of KCl must be used to create this saturated solution? This solution is cooled to 10°C and the excess KCl precipitates (settles out). The resulting solution is saturated at 10°C. How many grams of KCl precipitated out of the original solution? KCl 90 g Hint: 200 g of water was used – table G is for 100 g of water 30 g

Colligative Properties The affect of a solute on solvent due to the nature of the solute or concentration of the particles. Freezing Point Depression- lowers the freezing point of a solvent by interfering with crystalization Boiling Point Elevation- raises the boiling point

These properties are dependent on the number or particles and the type of particle dissolved Ionic Solutes break up into ions NaCl = Na+ + Cl-1 There are 2 pieces The more ions created the more pieces and the more the boiling and freezing point are affected AlCl3  Al +3 + 3Cl -1 There are 4 pieces here Covalent compounds do not dissociate in water C6H12O6 remains together as 1 piece Polyatomic ions are covalent and stay together as one piece Mg(NO3)2 Mg+2 + 2NO3-1 Three pieces