CHAPTER 13

CHAPTER 13 SOLUTIONS

SOLUTION REVIEW • Solutions are homogenous mixtures. • They consist of a larger component called the solvent and one or more smaller componentscalled the solutes. • Can be in the solid, liquid, or gaseous state.

Solution Examples • Margarine • Tap Water • Steel • 18 Carat Gold • Air • Sterling Silver

Solution Examples Composition of air: Dry air contains roughly (by volume) 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% What is the solvent in air ?

Solution Examples Composition of air: Dry air contains roughly (by volume) 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% What is the solvent in air ? Nitrogen, N2

Solution Examples Composition of air: Dry air contains roughly (by volume) 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% What is the solvent in air ? Nitrogen, N2 What is a solute in air?

Solution Examples Composition of air: Dry air contains roughly (by volume) 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% What is the solvent in air ? Nitrogen, N2 What is a solute in air? Oxygen, O2

Solution Examples Composition of 18 carat gold: 75% gold, 12.5% silver, 12.5% copper. What is the solvent in 18 ct gold ?

Solution Examples Composition of 18 carat gold: 75% gold, 12.5% silver, 12.5% copper. What is the solvent in 18 ct gold ? Gold

Solution Examples Composition of 18 carat gold: 75% gold, 12.5% silver, 12.5% copper. What is the solvent in 18 ct gold ? Gold What are the solutes?

Solution Examples Composition of 18 carat gold: 75% gold, 12.5% silver, 12.5% copper. What is the solvent in 18 ct gold ? Gold What are the solutes? Silver and Copper

Solution Examples Examples of solutions include: Salt water: what is the solvent in salt water ?

Solution Examples Examples of solutions include: Salt water: what is the solvent in salt water ? Water, H2O

Solution Examples Examples of solutions include: Salt water: what is the solvent in salt water ? Water, H2O What is a solute in sea water?

Solution Examples Examples of solutions include: Salt water: what is the solvent in salt water ? Water, H2O What is a solute in sea water? NaCl (salt)

Solution Properties • Some general propertiesof solutions include: • Solutions may be formed between solids, liquidsor gases. • They are homogenous in composition • They do not settle under gravity • They do not scatter light (Called the Tyndall Effect) Solute particles are too small to scatter light and therefore light will go right through a solution like is shown on the next slide.

Tyndall Effect Laser light reflected by a colloid. In a solution you would not see any red light.

Solubility Soluble substances are those that can dissolve in a given solvent. Insoluble or immiscible substances are those that cannot dissolve in a given solvent. Which of the following are soluble in water? NaCl, sugar, cooking oil, alcohol, gasoline, motor oil

Solubility Soluble substances are those that can dissolve in a given solvent. Insoluble or immiscible substances are those that cannot dissolve in a given solvent. Which of the following are soluble in water? NaCl, sugar, cooking oil, alcohol, gasoline, motor oil Which of the following are immiscible in cooking oil? NaCl, sugar, alcohol, gasoline, motor oil, water

Solubility The maximum amount of a given solute a solvent can dissolve is called the solubility. The solubility is dependent on the temperature and pressure. Solubility is often expressed in terms of grams of solute per 100 g of solvent but may have other units. When a solvent contains the minimumamount of a solute possible the solutions is said to be unsaturated. When a solvent contains the maximum amount of a solute possible the solutions is said to be saturated. When a solvent contains more than the maximum amount of a solute possible the solutions is said to be supersaturated.

Solubility Solutions form when a soluble solute(s)is dissolved in a solvent. In biological systems aqueous (solutions where water is the solvent) are of particular importance. The solubility of most liquids and solids in water increases with temperature. The effect of pressure on the solubility of liquid or solid solutes in water is negligible.

Solubility Curves of Various Solutes

Supersaturated Solutions By forming a solution at a high temperaturethen slowly cooling it we can form supersaturatedsolutions that contain more solutethan in a saturated solution. These kinds of solutions are very unstableand tend to separate out the excess solutewith the slightest disturbance. http://www.youtube.com/watch?v=uy6eKm8IRdI&NR=1 http://www.youtube.com/watch?v=aC-KOYQsIvU&feature=related

Solubility The solubility of gases in water decreases with temperature. • Are cold carbonated drinks bubblier than warm carbonated drinks? The solubility of many gases in water is directly proportionalto the pressure being applied to the solution. i.e. double the pressure, double the solubility • What happens when the cork is removed from a bottle of champagne? • What is the origin of decompression sickness? • Anyone heard of hyperbaric therapy?

SOLUTION FORMATION When we place an ionic solid in water there will be attractive forcesbetween theionsat the surface of the crystal and the water molecules. These attractive forces are called ion-dipole forces. Water molecules orient such that the positive endof the molecule is oriented towards the negative ionsat the surface and vice versa.

Solution Formation How do solutions form? Why do some substances leave one phase and enter the solution and others don’t? How can we use chemistry to predict solubility's? Lets first look at the formation of a solution between an ionicsoluteand a polar solventsuch as H2O.

Solution Formation Ionic compoundsare composed of oppositely chargedions arranged in a repeating 3-d arrangement. They are held together by attractive forcesbetween oppositely charged ions.

Solution Formation Ionic compoundsare composed of oppositely chargedions arranged in a repeating 3-d arrangement. They are held together by attractive forcesbetween oppositely charged ions Why is chloride ion larger than sodium ion?

SOLUTION FORMATION red is the region where electrons are found most oftenand blue is where electrons are rarely found

H2O K+ SOLUTION FORMATION If the attractive forcebetween the surfaceionand the solvent is greater than the forces between the ion and the solid then the ion will enter the solution phase. The ion that has left the solid and becomes completed surroundedby water molecules. It has become solvated orhydrated.

SOLUTION FORMATION Note the different orientation of water molecules around the oppositely charged ions. Positive pole of water directed to the negative ions and the negative pole directed to the positive ions

SOLUTION FORMATION In a solution of an ionic compounda solvated ion will occasionally collide with the surface of the solid. Sometimes when this happens the ion will “stick” to the surface and become part of the solid phaseagain. This will happen more frequently the more concentrated the solution is.

SOLUTION FORMATION When the rate of ions leaving the solid equals the rate of ions going backto the solid the system is at equilibrium and the solution is saturated. When a solution is at equilibrium with its solute macroscopically there will be no change occurring. However, at the molecular level lots is happening, just in equal and opposite directions.

SOLUTION FORMATION Supersaturated solutionscan form because there are no sitesfor solute ions to collide with. When we place a “seed”crystal in a supersaturated solution this provides the needed sites and the excess solute crystallizes very quickly.

SOLUTION FORMATION In the you tube video we watched you can just see the tiny seed crystals on the persons finger.

SOLUTION FORMATION Polar but non-ionic solutes dissolve in water via a similar mechanism as for ionic compounds.

SOLUTION FORMATION • A solute will be insoluble in a solvent if: • Forces between solute particles are greater than the forces between solute particles and the solvent.

SOLUTION FORMATION • A solute will be insoluble in a solvent if: • Forces between the solvent particles are stronger than forces between the solvent and the solute. • e.g. The only attractive force between oil and water will is dispersion forces. These are weak compared to hydrogenbonds between water molecules.

SOLUTION FORMATION In a polar solvent there will be attraction between the oppositely charged ends of the molecule. Hydrogen bonds are represented by dotted lines between the water molecules. A hydrogen bond is and intermolecular force between hydrogen of one molecule and O, N, or F of another molecule. Hydrogen must be directly attached to O, N, or F in at least one of the two hydrogen bonded molecules.

SOLUTION FORMATION A good “rule of thumb” that works especially well for non-ionic compoundsis: “Like dissolves like” i.e.Polarsolvents dissolve polar solutes well and non-polar solvents dissolve non-polar solutes well.

SOLUTION RATE • The rate of dissolution is dependent upon: • The surface areaof the solute. • i.e. how finely divided it is. Increasing rate

SOLUTION RATE • How hot the solution is. • i.e. the kinetic energyof solute and solvent. • The rate of stirring. Typically when we are preparing a solution in the lab we will both heat and stir.

SOLUTION RATE When a solute dissolves in a solvent heat can be released or absorbed. When heat is absorbed the process is endothermic and the solution becomes cooler. This effect is used in instant cold packsfor sporting injuries and first aid.

HEAT OF SOLUTION Endothermic Solution Solvent temperature 22.2° Solvent temperature 11.3°

HEAT OF SOLUTION Exothermic Solution More commonly dissolution is an exothermic process and heat is released when a solute is dissolved. Sometimes when we make a solution it will get so hot it boils!!

SOLUTION CONCENTRATION The ratio of the amount of solute to amount of solution, or solvent is defined by the concentration. solute solute Concentration = = solvent solution There are various combinations of units that are used in these rations. Ratio X 102 X 103 X 106 X 109 g solute ppb (w/w) ppm (w/w) ppt (w/w) % (w/w) = g solution g solute ppt (w/v) ppm (w/v) ppb (w/v) = % (w/v) mL solution mL solute = % (v/v) ppt (v/v) ppb (v/v) ppm (v/v) mL solution

SAMPLE SOLUTION PROBLEMS • 1. Find the % (w/w) when 25.2 g NaCl is combined with 33.6g H2O. • Find the mass of water and salt required to make 333 g of a • 44.6 % (w/w) solution. 25.2 g NaCl

SAMPLE SOLUTION PROBLEMS 1. Find the % (w/w) when 25.2 g NaCl is combined with 33.6g H2O. 2. Find the mass of water and salt required to make 333 g of a 44.6 % (w/w) solution. 25.2 g NaCl 33.6g H2O + 25.2 g NaCl

CHAPTER 13

CHAPTER 13

Presentation Transcript

CHAPTER 13

CHAPTER 13

Chapter 13

chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13

Chapter 13