Concentration of Solutions

Concentration is a measure of the amount of solute dissolved in a solution. There are many ways to measure the concentration.

Concentration is a measure of the amount of solute dissolved in a solution. There are many ways to measure the concentration.  Percent (part per hundred), ppb, ppm, etc  Usually by volume if using a liquid dissolved in a liquid  Usually by mass if using a solid dissolved in a liquid  Molality (m)  Mole fraction  Molarity (M)

Concentration is a measure of the amount of solute dissolved in a solution. There are many ways to measure the concentration.  Percent (part per hundred), ppb, ppm, etc  Usually by volume if using a liquid dissolved in a liquid  Usually by mass if using a solid dissolved in a liquid  Molality (m)  Mole fraction  Molarity (M) These are all quantitative. What would be a qualitative word for measuring concentration?

Percent =

Percent = mass of solute x 100 mass of solution

Example 1: What is the % concentration of a solution made by dissolving 17g of sucrose in 183g of water?

Example 2: What would the solution in #1 be in ppm? ppb?

Example 3: What would the % concentration be of a solution made by combining 45g of KCl in 100g of water?

Example 4: What would be the new concentration if 155g of water were added to the solution in #3?

Molality =

Molality = moles of solute / kilograms of solvent What is an advantage to using molality over molarity?

Molality = moles of solute / kilograms of solvent What is an advantage to using molality over molarity? Molality is unaffected by temperature.

Example 5: What is the molality of a solution made by adding 16.1g of chlorine gas to 5000g of water?

Example 6: What is the molality of a solution made by adding 125g of iodine to 750g of carbon tetrachloride (CCl 4 )?

Mole fraction =

Mole fraction = moles of solute / total moles

Example 7: What is the mole fraction of sulfur dioxide in a solution containing 128g of sulfur dioxide dissolved in 1500g of carbon dioxide?

Example 8: A gas mixture contains 50.4g of dinitrogen monoxide and 65.2g of oxygen gas. What is the mole fraction of dinitrogen monoxide?

Molarity =

Molarity = moles of solute / liters of solution

Example 9: What is the molarity of a solution formed by mixing 10.0g of sulfuric acid (H 2 SO 4 ) with enough water to make 100.0mL of solution?

Example 10: Vinegar is a solution of acetic acid (CH 3 COOH). What is the molarity of a solution produced when 125g of acetic acid is dissolved in water to make 1.50L of solution?

Example 11: How many grams of bromine are needed to prepare 0.500L of a M solution of bromine in water?

Example 12: What volume (in mL) of a 0.500M solution of copper (II) sulfate is needed to react with an excess of aluminum to provide 11.0g of copper?

Example 13: Commercial hydrochloric acid, HCl, is 12.0M. Calculate the mass of HCl in 250mL of solution.

Example 14: An excess of zinc is added to 125mL of 0.100M HCl. What mass of zinc chloride is formed?

Example 15: Yellow CdS pigment is prepared by reacting ammonium sulfide with cadmium nitrate. What mass of CdS can be prepared by mixing 2.50L of 1.25M cadmium nitrate solution with an excess of ammonium sulfide solution?

When solvent is added to a solution, the number of moles does not change, but the molarity does.

When diluting a solution, only the volume changes, not the moles of solute.

When solvent is added to a solution, the number of moles does not change, but the molarity does. M 1 V 1 = M 2 V 2 M = molarity V = volume

Example 16: How many milliliters of 3.0M H 2 SO 4 are required to make 450mL of 0.10M H 2 SO 4 ?

Example 17: How many milliliters of 5.0M K 2 Cr 2 O 7 solution must be diluted in order to prepare 250mL of 0.10M solution?

Chapter 12 Test 15 multiple choice (4 points each) 8 problems (5 points each) 1 extra credit (5 points) heterogeneous mixture (colloids and suspensions) vs homogeneous mixture (solutions) miscible vs immiscible saturated, unsaturated, and supersaturated solubility graphs (5 questions) “like dissolves like” solubility of gases vs solubility of solids process of solvation in aqueous solvent = enthalpy of solution dissolution of solute (breaking bonds, endothermic) solvent pulling solute apart hydration (reforming bonds, exothermic) water forming bonds with solute

ways to increase the rate of solvation molarity (M) molality (m) % composition mole fraction dilutions involving molarity stoichiometry involving solutions