V. Solutions

2 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. Dissolved particles are too small to be trapped by a filter

3 Regents Question: Which mixture can be separated by using the equipment shown? (1) NaCl(aq) and SiO 2 (s) (2) NaCl(aq) and C 6 H 12 O 6 (aq) (3) CO 2 (aq) and NaCl(aq) (4) CO 2 (aq) and C 6 H 12 O 6 (aq) (aq) stands for aqueous which means dissolved in water. Dissolved particles are too small to be trapped by the filter.

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

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

6 A solution which is on the line is saturated A solution below the line is unsaturated A solution above the line is supersaturated

7 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

8 Regents Question: According to Reference Table G, which solution is saturated at 30°C? (1) 12 grams of KClO 3 in 100 grams of water (2) 12 grams of KClO 3 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

9 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

10 Which are gases?

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

12 Regents Question: When cola, a type of soda pop, is manufactured, CO 2 (g) is dissolved in it. A capped bottle of cola contains CO 2 (g) under high pressure. When the cap is removed, how does pressure affect the solubility of the dissolved CO 2 (g)? A glass of cold cola is left to stand 5 minutes at room temperature. How does temperature affect the solubility of the CO 2 (g)?

13 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 Dry cleaners use a nonpolar solvent to get rid of oil and grease Liquids that dissolve each other are called miscible liquids. (Polar) ( Nonpolar )

14 Regents Question: 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.

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

16 Soluble Not Soluble

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

18 Regents Question: According to Table F, which of these salts is least soluble in water? (1)LiCl (2) RbCl (3) FeCl 2 (4) PbCl 2

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

20 Regents Question: 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 Molarity = Moles Liters

21 Regents Question: 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

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

23 Regents Question: 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 H 2 O B - 20 grams /60 grams H 2 O C - 30 grams /120 grams H 2 O D - 40 grams/80 grams H 2 O

24 Regents Question: 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?

25 The addition of a nonvolatile solute to a solvent causes the boiling point of the solvent to increase and the freezing point of the solvent to decrease. The greater the concentration of particles, the greater the effect. SoluteMoles of particles per mole of solute C 6 H 12 O 6 1 (Non-electrolytes do not separate into ions) NaCl2 (1-Na + and 1 Cl - ) CaF 2 3 (1-Ca 2+ and 2 F - ) H 2 SO 4 3 (2-H + and 1 SO 4 2- )

26 Regents Question: At standard pressure when NaCl is added to water, the solution will have a (1) higher freezing point and a lower boiling point than water (2) higher freezing point and a higher boiling point than water (3) lower freezing point and a higher boiling point than water (4) lower freezing point and a lower boiling point than water

27 Regents Question: Compared to pure water, an aqueous solution of calcium chloride has a (1) higher boiling point and higher freezing point (2) higher boiling point and lower freezing point (3) lower boiling point and higher freezing point (4) lower boiling point and lower freezing point

28 The structure and arrangement of particles and their interactions determine the physical state of a substance at a given temperature and pressure. SolidLiquidGas

29 Intermolecular forces created by the unequal distribution of charge result in varying degrees of attraction between molecules. Hydrogen bonding is an example of a strong intermolecular force. Dipole-Dipole attraction between polar molecules

30 Hydrogen bonds occur when hydrogen is bonded to a small, highly electronegative atom.  N, O and F can have hydrogen bonds when hydrogen is bonded to it.  Account for the unusual properties of water:  High boiling point, surface tension, six sided snowflake

31 Physical properties of substances can be explained in terms of chemical bonds and intermolecular forces. Ionic bonds are strong Hydrogen bonds are strong intermolecular forces Polar molecules exhibit attraction between the + and – sides of their molecules Bonds between nonpolar molecules are weak. The more protons in the molecule, the stronger these forces.

32 Regents Question: The strongest forces of attraction occur between molecules of (1) HCl (3) HBr (2) HF (4) HI

33 These properties include conductivity, malleability, solubility, hardness, melting point, and boiling point.  The stronger the intermolecular forces, the higher the boiling point and melting point.  The stronger the intermolecular forces, the lower the vapor pressure. –See Table H

34 Table H – the vapor pressure of four liquids at various temperatures. As temp inc, vapor pressure inc.

35 Regents Question: According to Reference Table H, what is the vapor pressure of propanone at 45°C? (1)22 kPa (2)33 kPa (3)70. kPa (4) 98 kPa

36 A liquid will boil when its vapor pressure equals the atmospheric pressure.  Raising the temperature will increase the vapor pressure of the liquid  Lowering the atmospheric pressure will lower the boiling point –On top of a high mountain, water boils at a temperature below 100  C

37 Standard pressure is kilopascals (kPa) or 1 atmoshpere (atm) The normal boiling point occurs when the atmospheric pressure is kPa (standard pressure) The normal boiling point of ethanol is 80ºC.

38 Regents Question: As the pressure on the surface of a liquid decreases, the temperature at which the liquid will boil (1) decreases (2) increases (3) remains the same

39 Regents Question: As the temperature of a liquid increases, its vapor pressure (1) decreases (2) increases (3) remains the same

40 Regents Question: The vapor pressure of a liquid is 0.92 atm at 60°C. The normal boiling point of the liquid could be (1) 35°C (3) 55°C (2) 45°C (4) 65°C

41 Regents Question: What is the vapor pressure of liquid A at 70°C? Your answer must include correct units.

42 Regents Question: At what temperature does liquid B have the same vapor pressure as liquid A at 70°C? Your answer must include correct units.

43 Regents Question: Which liquid will evaporate more rapidly? Explain your answer in terms of intermolecular forces.