Materials to take notes Greetings! Mixtures & Solutions Today you need: Materials to take notes

The GPS Standard SC7. Students will characterize the properties that describe solutions and the nature of acids and bases. a. Explain the process of dissolving in terms of solute/solvent interactions b. Observe factors that effect the rate at which a solute dissolves in a specific solvent, c. Express concentrations as molarities, d. Prepare and properly label solutions of specified molar concentration, e. Relate molality to colligative properties.

Solubility Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temperature based on a saturated solution

SUPERSATURATED SOLUTION Solubility UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form Maximum amount of a solute that can dissolve in a solvent at a specified temperature and pressure is its solubility. – Solubility is expressed as the mass of solute per volume (g/L) or mass of solute per mass of solvent (g/g) or as the moles of solute per volume (mol/L). – Solubility of a substance depends on energetic factors and on the temperature and, for gases, the pressure. • A solution that contains the maximum possible amount of solute is saturated. • If a solution contains less than the maximum amount of solute, it is unsaturated. When a solution is saturated and excess solute is present, the rate of dissolution is equal to the rate of crystallization. • Solubility increases with increasing temperature — a saturated solution that was prepared at a higher temperature contains more dissolved solute than it would contain at a lower temperature, when the solution is cooled, it can become supersaturated. increasing concentration

Solubility Curves Solubility of solids increase with increases in temperature. Solubility of gases in liquids decrease with increasing temperature WHY?

The Effect of Temperature on Solubility is dependent on the phase of matter. Solids or liquids dissolved in liquids Gases dissolved in liquids To S To S As To , solubility As To , solubility

What is the solubility of____ at ____°C?

Solution Concentration

Think About it… you probably are familiar with the difference between what is called a "weak" solution or a "strong" solution. 

Concentration… The measure of how much solute is dissolved in a specific amount of solvent or solution. a measure of solute-to-solvent ratio concentrated vs. dilute “lots of solute” “not much solute” “watery” Concentration of a solution describes the quantity of a solute that is contained in a particular quantity of solvent or solution Knowing the concentration of solutes is important in controlling the stoichiometry of reactant for reactions that occur in solution A concentrated solution contains a large amount of solute in a given amount of solution. A 10 mol/L solution would be called concentrated. A dilute solution contains a small amount of solute in a given amount of solution. A 0.01 mol/L solution would be called dilute. Add water (hydrate) to dilute remove water (evaporate by boiling) to concentrate

Concentrations Qualitative (words): -Concentrated -dilute Quantitative (numbers): -percent by mass -percent by volume -Molarity (M) -molality (m)

What is the [solid solute] in a liquid solvent. What part What is the [solid solute] in a liquid solvent? What part? Out of what whole? Read the above as: What is the concentration of solid solute in a liquid solvent?

Percent by Mass Mass of Solvent? Mass of solution = Percent by mass = mass of solute x 100 mass of solution Use when combining a solid solute into a liquid solvent Mass of solution = mass of solute + mass of solvent Mass of Solvent?

Finding Mass of Solvent Or finding the mass of a volume. Is there a relationship b/w mass and volume? -- Density or D -- D = m/V or m = DV Since our solvent is H2O and we know that the DH2O = 1.0 g/ml (constant) So, m = DV or m = (1.0 g/ml) (V)

Example Percent by Mass: To maintain a sodium chloride (NaCl) concentration similar to ocean water, an aquarium must contain 3.6 g NaCl per 100.0 g of water. What is the percent by mass of NaCl in the solution? Equation: Percent by mass = mass of solute x 100 mass of solution Given: Mass of solute: 3.6 g NaCl Mass of solvent: 100.0 g H2O = 3.6 g NaCl x 100 3.6 g NaCl + 100.0 g H2O = 3.5 %

What is the percent by mass of NaHCO3 in a solution containing 20 What is the percent by mass of NaHCO3 in a solution containing 20.0 g of NaHCO3 dissolved in 600.0 mL of H2O?

But what if the solute and solvent are both liquids?

What does this mean?

Percent by Volume volume of solute Percent by volume = x 100 volume of solution

Try Calculating Percent by Volume: What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved in 155 mL of water? Percent by volume = volume of solute x 100 volume of solution

How much isopropyl alcohol is actually in a 473 mL solution of 99 % isopropyl alcohol? Percent by volume = volume of solute x 100 volume of solution

Molarity The unit M is read, “molar” Molarity (M) = moles of solute Liters of solution The unit M is read, “molar”

Calculating Molarity: What is the molarity of an aqueous solution containing 0.22 mol of glucose (C6H12O6) in 1.5 L of solution?

A 100. 5 mL solution contains 5. 10 g of glucose (C6H12O6) A 100.5 mL solution contains 5.10 g of glucose (C6H12O6). What is the molarity of this solution? (The molar mass of glucose is 180.16 g/mol.)

Remember, Molarity is just a measure of how concentrated a solution is (or how “strong” it is)… so, Which is the most concentrated solution? a) 0.50 M CuSO4 b) 1.75 M CuSO4 c) 3.00 M CuSO4 d) 7.00 M CuSO4

Which is the least concentrated solution? a) 0.25 M HCl b) 0.75 M HCl c) 2.00 M HCl d) 4.25 M HCl

We know from Guy Lussac’s Law that V of a solution changes with T. This change in V alters the M of the solution. We also know that mass does not change with T. So, sometimes it is more useful to describe solutions in terms of how many moles of solute are dissolved in a specific mass of solvent.

Molality Molality (m) = moles of solute kg of solvent You LOVE me!! The unit m is read, “molal”

Calculating Molality: In the lab, a student adds 4.5 g of sodium chloride (NaCl) to 0.1 kg of water. Calculate the molality.

What is the molality of a solution containing 10 What is the molality of a solution containing 10.0 g of Na2SO4 dissolved in 2000.0 g of water?

In the lab, you might use concentrated solutions of standard molarities, called stock solutions. But, you can prepare a less-concentrated solution by diluting the stock solution with additional solvent.

Making a Dilute Solution remove sample moles of solute initial solution same number of moles of solute in a larger volume mix Making a Dilute Solution diluted solution

Dilution Preparation of a desired solution by adding water to a concentrate. Moles of solute remain the same. M = Molarity (Concentration), V = volume

M1V1 = M2V2 Dilution Equation: M1 and V1 represent the molarity and volume of the stock solution, while M2 and V2 represent the molarity and volume of the dilute solution.

So for instance, what volume, in mL, of a 2 So for instance, what volume, in mL, of a 2.00M calcium chloride (CaCl2) stock solution would you use to make 0.50 mL of 0.300M calcium chloride solution?

What volume of a 3. 00M KI stock solution would you use to make 0 What volume of a 3.00M KI stock solution would you use to make 0.300 L of a 1.25M KI solution?

Concentration “The amount of solute in a solution” A. % mass = mass of solute mass of sol’n B. % volume = V of solute V of sol’n C. molarity (M) = moles of solute L of sol’n – used most often in this class % by mass – medicated creams % by volume – rubbing alcohol MOLARITY - Most common unit of concentration Most useful for calculations involving the stoichiometry of reactions in solution Molarity of a solution is the number of moles of solute present in exactly 1 L of solution: moles of solute molarity = liters of solution Units of molarity — moles per liter of solution (mol/L), abbreviated as M Relationship among volume, molarity, and moles is expressed as VL M Mol/L = L (mol) = moles (L) There are several different ways to quantitatively describe the concentration of a solution, which is the amount of solute in a given quantity of solution. 1. Molarity – Useful way to describe solution concentrations for reactions that are carried out in solution or for titrations – Molarity is the number of moles of solute divided by the volume of the solution Molarity = moles of solute = mol/L liter of solution – Volume of a solution depends on its density, which is a function of temperature 2. Molality – Concentration of a solution can also be described by its molality (m), the number of moles of solute per kilogram of solvent – Molality = moles of solute kilogram solvent – Depends on the masses of the solute and solvent, which are independent of temperature – Used in determining how colligative properties vary with solute concentrations 3. Mole fraction – Used to describe gas concentrations and to determine the vapor pressures of mixtures of similar liquids – Mole fraction () = moles of component total moles in the solution – Depends on only the masses of the solute and solvent and is temperature independent 4. Mass percentage (%) – The ratio of the mass of the solute to the total mass of the solution – Result can be expressed as mass percentage, parts per million (ppm), or parts per billion (ppb) mass percentage = mass of solute  100% mass of solution parts per million (ppm) = mass of solute  106 parts per billion (ppb) = mass of solute  109 – Parts per million (ppm) and parts per billion (ppb) are used to describe concentrations of highly dilute solutions, and these measurements correspond to milligrams (mg) and micrograms (g) of solute per kilogram of solution, respectively – Mass percentage and parts per million or billion can express the concentrations of substances even if their molecular mass is unknown because these are simply different ways of expressing the ratios of the mass of a solute to the mass of the solution M = mol L D. molality (m) = moles of solute kg of solvent E. M1V1 = M2V2 dilutions