DO NOW • Pick up notes and handouts • Handouts are due tomorrow • Book projects due Friday: William B., Marwa J., Quinn R., Devon L., Andrew C., Madison B., Peter D., Seth T., Conner R., Kat M., Tatum N., Sam W., Dan N., Claire W., and Jamal R.
HANDOUTS – due tomorrow For the CONCEPT REVIEW: Solutions handout you need to know something about a few of the solutions listed in Table 1: hexane/cyclohexane – nonpolar benzene – nonpolar methanol (alcohol) - polar
If you are not part of the SOLUTION, you’re part of the PRECIPITATE! SOLUTIONS Chapter 15
SOLUTION OBJECTIVES • Differentiate between colloids, solutions, and suspensions • Define solvent and solute and be able to identify them in a solution. • Describe the process of solvation, dissociation, and dissolving. • Be sure to study polarity of compounds to be able to predict solubility. • Differentiate between saturated, unsaturated, and supersaturated. • State and discuss the factors affecting the rate of solubility. • State and discuss the factors that affect solubility. • Be able to read a solubility curve graph. • Relate the enthalpy of solution to endothermic and exothermic dissolving processes. • Differentiate between molarity and molality. • Solve problems involving molarity, molality, mole fraction mass percent, volume percent, and making solutions.
THREE TYPES OF MIXTURES SOLUTION COLLOID SUSPENSION
DEMO SOLUTION: Salt and water COLLOID: Shaving gel SUSPENSION: Cornstarch in water TYNDALL EFFECT: particles dispersed in mixture are big enough to scatter light.
SOLUTIONS • A solution is a homogeneous mixture of two or more substances in a single physical state. • SOLVENT: the substance doing the dissolving and in the greater amount. • SOLUTE: the substance being dissolved and in less abundant.
DEMO • If I combine 50mL beads and 50.0mL sand, what will the final volume be? • If I combine 50.0mL water (green) and 50.0mL alcohol, what will the final volume be?
NINE BASIC TYPES OF SOLUTIONS Liquid Solutions: • solid in liquid (salt water) • liquid in liquid (vinegar) • gas in liquid (carbonated drink) Gaseous Solutions:All gaseous mixtures are solutions • solid in gas (soot in air) • liquid in gas (humid air) • gas in gas (air)
NINE BASIC TYPES OF SOLUTIONS Solid Solutions Homogeneous mixtures of solids are usually made from liquid solutions that have been mixed and then solidified (frozen) • solid in solid (alloys – brass, bronze) • liquid in solid (dental fillings) • gas in solid (charcoal gas mask)
SOLUTION EQUILIBRIUM • A solution is in dynamic equilibrium when the number of solute particles returning to the crystal surface is equal to the number of solute particles leaving the crystal surface.
SOLUTION EQUILIBRIUM • A SATURATED solution is a solution with the maximum amount of solute dissolved at a given temperature (Any more added goes to the bottom). It has reached dynamic equilibrium. • An UNSATURATED solution has the ability to dissolve more solute at a given temperature • If a solution is SUPERSATURATED, then a hot solution is saturated and cooled. An unstable condition results because the solution holds more solute that it normally does at a given temperature.
LASERDISC SOLUTIONS – Chapter 20 • What are ion-dipole attractions? During the process of solvation, how do ion-dipole attractions compare to the ionic bonds inside an ionic crystal? • Describe the processes that are balanced when solubility equilibrium has been reached. If more solute is added to a solution in equilibrium, will this always result in more dissolved solute particles in the solution? Explain. • How does a solution become supersaturated? After crystals precipitate out of a supersaturated solution, would you still call it supersaturated? Explain.
THE DISSOLVING PRACTICE • Dissolving occurs when the solute is pulled apart by the solvent. • This takes place at the surface of the solute. The solvent surrounds the solute. • This process of surrounding the solute is called SOLVATION. • When the surrounding is done by water, this is called HYDRATION, a particular type of solvation. • When ionic compounds separate into their ions in a solvent, DISSOCIATION occurs.
Solute-Solvent Combinations 1. Polar Solvent – Polar Solute: The polar solvent is attracted to the polar solute. The solvent gradually surrounds the solute. The particles attach themselves due to polar attraction. Solvation occurs. Like dissolves like. Ex. Salt and water
Solute-Solvent Combinations 2. Polar Solvent – Nonpolar Solute: Polar solvent particles are attracted to each other and not the solute. Solvation does not occur and a solution is unlikely. Ex. oil and water DEMO: Marbles
Solute-Solvent Combinations 3. Nonpolar Solvent – Polar Solute: Nonpolar solvent particles have little attraction to the polar solute. Solvation does not occur and a solution is unlikely. Ex. Salt and oil
Solute-Solvent Combinations 4. Nonpolar solvent – nonpolar solute: Random motion of solute particles causes them to leave the surface of the solute and become evenly dispersed in the nonpolar solvent. Solvation occurs. Like dissolves like.
LASERDISC Polar and Nonpolar Solvents – Chapter 30 • Why are some liquids immiscible? Explain in terms of intermolecular forces? • How would you predict whether carbon tetrachloride is a polar or nonpolar solvent? What evidence have you observed that supports your prediction? • Based on chemical formula alone, can you tell whether iodine, I2, is a polar or nonpolar solute? What evidence have you observed that supports your prediction? • Based on the chemical formula alone, can you tell whether copper (II) chloride, CuCl2, is a polar or nonpolar solute? What evidence have you observed that supports your prediction?
DO NOW • Pick up handout – due Tuesday • Turn in Superaturation lab • Book projects due today: William B., Marwa J., Quinn R., Devon L., Andrew C., Madison B., Peter D., Seth T., Conner R., Kat M., Tatum N., Sam W., Dan N., Claire W., and Jamal R.
SOLUBILITY • Solubility is how much solute can dissolve in a given amount of solvent. • It is measured in g/L or mol/L. It is usually the grams of solute per 100g of solvent. • A CONCENTRATED solution is said to have a high ratio of solute to solvent. • A DILUTE solution is the opposite of this. • For solids: solubility usually increases with increased temperature • For gases: solubility usually decreases with increased temperature
SOLUBILITY How do you determine saturated, unsaturated, and supersaturated for a given substance?
FACTORS AFFECTING SOLUBILITY • Nature of the solvent and solute - “like dissolves like”. This means that polar solvent dissolves a polar solute and nonpolar solvent dissolves nonpolar solute. But polar does not dissolve nonpolar. In other words – will it even dissolve?
FACTORS AFFECTING SOLUBILITY • Temperature - increase the temperature and solubility increases (except gases).
FACTORS AFFECTING SOLUBILITY 3. Pressure - increase the pressure and you increase solubility (only with gases). Gases ONLY 4. How much is already dissolved– saturated versus unsaturated versus supersaturated…
Factors Affecting RATE of Solubility (How fast something will dissolve) • Agitation (shaking, stirring) • Increased temperature (except gases) • Smaller Particle size Each allows more solvent to come in contact with the solute faster.
HEAT OF SOLUTION • Energy is released and absorbed as substances dissolve. • ENDOTHERMIC: The solute particles must separate and the solvent particles must separate to make room for the solute. • EXOTHERMIC: When the solute and the solvent mix, the particles are attracted to each other. • The overall change in energy is the heat of solution. • Most solutions are endothermic.
CONCENTRATION Concentration is NOT dependent upon the sample size and it can be measured. • Grams/100.0 grams measures solubility • Parts per million (ppm) measures small concentrations • Parts per billion (ppb) measures pollutants • Molarity used in lab chemistry • Molality used for special calculations We will learn to calculate molarity, molality, mass percent, volume percent, and mole fraction
MOLARITY, M This is the ratio between the moles of dissolved substance and the volume of the solution expressed in liters. Molarity, M = moles of solute volume of solution in liters A one-molar (1M) solution of HCl contains one mole of HCl in one liter of water. (Which means it contains 36.46g of HCl in 1 liter of water.)
SAMPLE PROBLEM Sandy dissolves 45.0 g of NaCl in 2.5 liters of solution. What is the concentration in molarity of NaCl? Mass = 45.0 g Molar Mass = 58.44 g/mol V = 2.5 L Molarity = 45.0 g NaCl 1 mol NaCl 2.5 L 58.44 g NaCl = 0.31M
PRACTICE What is the molarity of 58.5g of NaCl dissolved in 2.0L of solution?
MOLALITY, m This is concentration expressed in terms of moles of solute per kilogram of solvent. Volume is not a factor. Molality, m = moles solute Kg solvent A 1.0 molal aqueous sugar soln: 1 mole sugar 1 kg water
SAMPLE PROBLEM Calculate the molality of 98.0g RbBr in 0.824 Kg water. m = 98.0 g RbBr 1 mol RbBr 0.824Kg H2O 165.38g RbBr = 0.719m
PRACTICE Calculate the molality of 85.2g SnBr2 in 140.0g water.
MASS PERCENT Scientists frequently express the concentration of solutions in mass percent. Mass % = g of solute x 100 g of solute + g of solvent A 5% solution of NaOH contains 5g NaOH in each 100g of solution (95g solvent and 5g of solute).
VOLUME PERCENT Consumer products frequently express their concentration of solutions in volume percent. Volume % = L of solute x 100 L of solute + L of solvent A 5% solution of sodium hydroxide contains .05L NaOH in each 1.0L of solution (0.95L solvent and 0.05L of solute).
MOLE FRACTION The concentration of solution can also be expressed in mole fractions. Mole Fraction = mole of solute mole of solute + mole of solvent
PREPARING SOLUTIONS A 3M solution of HCl is not bought but made from 12M stock solutions. In addition, a 1.0M solution of NaOH is made from a calculated amount of solid NaOH added to water. It is important to know how to make different concentration of solutions.
PREPARING SOLUTIONS Prepare 1.0 liter of a 1.0M aqueous solution of NaOH M = mol 1.0M = mol L 1.0L mol = (1.0M)(1.0L) = 1.0mol 1.0mol NaOH 40.00g NaOH = 40.00g 1 mol NaOH So, you will put 40.00gNaOH in a flask, add 1.0Lwater, and mix well.
Preparing Solutions Prepare 1.0L of a 6.0M aqueous solution of KCl. The molar mass of KCl is 74.55g/mol.
DILUTING SOLUTIONS To dilute a solution, you can form a ratio between molarity and volume. M1V1 = M2V2
DILUTING SOLUTIONS Diluting a 12.0M solution of HCl to 6.0M HCl What volume would you use to make 0.500L of 6.0M HCl solution? V1 = M2V2 = (6.0M HCl)(0.500L HCl) M1 (12.0M) = 0.250L HCl Thus you would need 0.250L HCl and 0.250L water to make the solution.
PRACTICE Preparing a 0.1M solution of HCl What volume would you use of 12.0MHCl to make 1.0L of 0.1MHCl?
ANSWER Preparing a 0.1M solution of HCl M1 = 12.0MHCl V1 = M2V2 V1 = ? M1 M2 = 0.1MHCl V1 = (0.1MHCl)(1.0L) V2 = 1.0L (12.0MHCl) = 0.0083L M1V1 = M2V2Add 8.3mL 12.0MHCl to 991.7mL water
HOMEWORK • Handout due Tuesday • Problem set due Wednesday Chapter 14 #9, 10, 16, 17, 21, 22, 24, 25, 27, 39, 41, 45, 46
Do Now • Get out lab logbook to copy potassium nitrate data from yesterday. • Book Problem set due tomorrow • Pick up handout – due Wednesday • Ice Cream Supplies due NEXT Tuesday • Book Projects due Thursday: Hayden R., Matt H., Bob Wiley, Sean R., Sam K., Cameron H., Joe F., Marshall C., Josh M., Kainath M., Grace M., Sarah., Adiba K., Alexander G., and Stilian I.
Copy data for your class • Plot data on the other side – ALL POINTS. • Remember that you dissolved 2.0g solute in 5.0mL (g) solvent which is equivalent to 40g salt solute in 100.0mL water solvent • Your explanation for #2 needs to be better than “It’s above the line”.
ICE CREAM ASSIGNMENTS • Everyone is assigned one item. • Bring non-refrigerated items in any day between now and March 12. • Bring refrigerated items in March 11 or 12 • All items for a class must be received by March 12 at 3:30 or no ice cream for that class. • Feel free to bring your own toppings!