Solutions Chapter 15 Coffee = solution Brass = solution Jayhawk says: Chemistry is awesome! Go KU!

The Triple “S” – solution, solvent, solute Solution: a homogeneous mixture in which the components are uniformly intermingled. Solvent: the dissolving medium; substance present in the largest amount Solute: substance dissolved in a solvent Solute + Solvent Jayhawk says: Did you know solutions with water as the solvent are Aqueous solutions?

The Triple “S” – solution, solvent, solute When a solid is being dissolved in a liquid to form a solution, three factors affect the speed of the dissolving process; Surface area, stirring and temperature. Solute + Solvent Jayhawk says: Did you know that the Jayhawks were the National Champions in basketball in 2008?

Solubility Solids Gases

The most commonly used expression of concentration is molarity. Jayhawk says: Rock Chalk Jayhawk!! Go KU!!

M = moles of solute liter of solution Examples: #1) A solution contains 0.90 mol of NaCl in 0.50 L of water. Calculate the M of this solution mol NaCl = 1.8 M 0.50 L H 2 O Jayhawk says: Remember to convert to liters if given milliliters. #2) A solution contains 1.2 g of Magnesium chloride in 100 mL of Water. Calculate the M.

Answer: 1.2g MgCl 2 x 1 mol MgCl 2 = 0.013mol MgCl g MgCl 2 Jayhawk says: Remember significant figure rules mol MgCl 2 = 0.13 M L H 2 O

Another Example!! A 0.40 M solution of glucose contains 8 moles of the solute. What is the volume of this solution? Jayhawk says: Chemistry RULES!!

Answer: Molarity = mol solute L of soln Jayhawk says: Remember significant figure rules. So, L (volume) of soln = mol solute Molarity L = 8 mol 0.40 M Volume = 20 L

Jayhawk says: Chemistry is my favorite class!! Molality is the number of moles of a given substance per kilogram of solvent. m = Moles of solute Kg of Solvent "one molal solution", i.e. a solution which contains one mole of the solute per 1000 grams of the solvent.

Jayhawk says: Who did the Jayhawks beat in the Orange Bowl last year? A solution is prepared by dissolving mol of NaCl in Kg of H20. Calculate the molality. A solution contains 1.5 mol of NaCl in 100. g of H20. Calculate the molality.

Jayhawk says: You need to know molality so we can make ice cream. How many g of potassium iodide must be dissolved in 500. g of water to give a molal solution?

Mole Fraction Ratio of the number of moles of solute to number of moles of solute and solvent (solution)

To concentrate a solution, one must add more solute, or reduce the amount of solvent (for instance, by selective evaporation). By contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute. The # of moles of solute stays constant. More H20 is added which increases the volume while decreasing the Molarity. Light, and able to see through, (lightly concentrated)

Dilution Equation: M (1) V (1) = M (2) V (2) M (1) V (1) are the initial conditions M (2) V (2) are the final conditions (dilute)

How would you prepare 100 mL of 0.40 M MgSO 4 from a stock solution of 2.0 M MgSO 4 ?

You have 1000 mL of 1.0 M HCl in your stockroom. You need 15 mL of 0.02 M solution for a lab. How much of the original solution will you need to make this solution?

Dilution Equation: M (1) V (1) = M (2) V (2) M (1) V (1) are the initial conditions M (2) V (2) are the final conditions (dilute)

 Saturated Solution  Unsaturated Solution  Supersaturated Solution Jayhawk says: I hope you learned something in this chapter, and remember, Rock Chalk Jayhawk!

- volume of solute x 100 volume of soln - used for liquids dissolved within liquids Jayhawk says: Listen up class, it’s time for an example. Calculate the % V of isoprpopanol when 20. mL of the alcohol Is diluted with water for a final volume of 100. mL A soln has a total V of 1000 mL after water was added to 25 mL of ethanol. What is the % V of the ethanol soln?

mass of solute x 100 mass of soln grams of solution = grams of solute + grams of solvent Jayhawk says: How many more days of school do we have? Answer on next page. A hydrochloric acid soln was made by adding g of HCl to 100 g H 2 0. Calculate the % mass of HCl in the soln. Calculate the mass % of octane when 10.5 g C 8 H 18 is mixed with 40.0 g of C 6 H 14. Octane is the solute.

mass of solute x 100 volume of soln most often seen with g/mL units, but g/L are o.k. (make sure to label) Jayhawk says: 45, After today!! Yippee!! A 100 mL soln containing 7.0 g of MgCl 2 is what % mass/volume of MgCl 2 ?

Jayhawk says: What is in that beaker of magnesium chloride solution? Calculating ion concentration from Molarity Solute concentration is always written in terms of the solute form before it dissolves. Now, we need to account for ions in soln, dissociation of ions when dissolved.

Jayhawk says: Don’t forget to always check your solubility table! Needed –Solubility Tables –Balanced Equations –Net Ionic Equations – M = [ ]

Give the [ ] of all ions in the soln below 0.50 M Co(NO 3 ) 2 Dissociation Rxn: Determine M of each ion:

Give the [ ] of all ions in the soln below 1.0 M FeCl 3 Dissociation Rxn: Determine M of each ion:

How many moles of Ag + ions are present in 25 mL of a 0.75 M AgNO 3 soln? Unk: Given: Dissoc. Rxn:

Jayhawk says: 22.4 L is for gases only!! Incorporating Stoichiometry, road maps, with new soln. info. Use M, molarity: mol, L as a conversion factor between moles and Liters L mol Never use 22.4 L. This is for gases only!! mol Many types of problems... Always start by writing a balanced equation Make a road map Write givens and unknown

1.0 L of M calcium nitrate reacts with 3.0 L M sodium chromate. What mass of the precipitate will form? Jayhawk says: This is a limiting reactant problem. Remember those?!! Rxn: Net Ionic: Road Map: Stoich:

What volume of 2.50 M soln of silver nitrate is needed to completely precipitate out 4.2 g of silver chloride? Jayhawk says: Don’t Forget, TEST Next Class!! Rxn: Net Ionic: Road Map: Stoich:

Ammonium phosphate and calcium chloride react g of the ppt forms from excess (NH 4 ) 3 PO 4 and 416 mL of a CaCl 2 soln. What must have been the [ ], in M of the CaCl 2 soln? Jayhawk says: Study, Study, Study!! Rxn: Net Ionic: Road Map: Stoich: