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Solubility & Solution Concentrations

Solubility & Solution Concentrations. SOLUBILITY. The maximum amount of solute that will dissolve in a given amount of solvent at a specific temperature Ex. Subst Solubility in 100 g Water 20 o C 60 o C 100 o C NaCl 35.9 37.1 39.2

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Solubility & Solution Concentrations

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  1. Solubility & Solution Concentrations

  2. SOLUBILITY • The maximum amount of solute that will dissolve in a given amount of solvent at a specific temperature • Ex. Subst Solubility in 100 g Water 20oC 60oC 100oC NaCl 35.9 37.1 39.2 (1) How does solubility vary with temperature? (2) What mass of sodium chloride will dissolve in 1.00 kg of water at 20oC?

  3. 3 Solution Situations SATURATED SOLUTION- contains the maximum amount of dissolved solute at specified temperature UNSATURATED SOLUTION- contains less than the maximum amount of solute SUPERSATURATED SOLUTION- contains more! (Formed by careful cooling of a solution saturated at a higher temperature)

  4. Testing for SaturationJust add a single crystal (xtal) What happens if you drop a single xtal of solute in a/an: SATURATED SOLUTION- Nothing, the xtal sinks or floats UNSATURATED SOLUTION – Xtal dissolves SUPERSATURATED SOLUTION- Many more xtals form!

  5. Solubility Graph • Which salt is least soluble at 10oC? • Which is least soluble at 303K? • List the compounds in order of increasing solubility at 30oC.

  6. The solubility of AgNO3 is 216 g per 100 g of water A student measures out 280 mL of water in a graduated cylinder. Then he adds 650 g of silver nitrate. • How much silver nitrate will dissolve? ____ g dissolved & ____ g are undissolved • What is the molar mass of silver nitrate? _____ g/mol 3. How many moles of AgNO3 are dissolved? ______ mol

  7. Concentration • The amount of solute present in a given amount of solvent or solution.

  8. ConcentrationMass Percent • Ex. What is the percent mass composition of a solution formed when 3.55 g NaCl is dissolved in 88 g of water? Mass Solute Mass % = X 100 Mass of Solution

  9. ConcentrationVolume Percent • Ex. A 250 mL bottle contains 21.5% alcohol by volume. What is the volume of the alcohol in the bottle? Vol Solute Vol % = X 100 Vol of Solution

  10. MOLAR CONCENTRATIONpopular concentration unitMOLARITY – the number of moles of solute that are dissolved in one liter of solution. • EX 1: What is the molarity of a solution formed when 1.35 mol of H2SO4 is dissolved in enough water to make 245 mL of solution. moles of solute Molarity (M) = liters of solution

  11. MOLAR CONCENTRATIONpopular concentration unit • EX 2: If 2.48 g of calcium fluoride is dissolved in 375 mL of solution, how should that solution be labeled. moles of solute Molarity (M) = liters of solution

  12. DILUTING SOLUTIONS • moles solute = MV • (M is molarity & V is volume) • If more solvent is added to a solution the concentration ___________ but the number of moles of solute remains the __________. • How many moles of KOH are there in 100 mL of 2.2 M KOH?

  13. “dilution equation”M1V1 = M2V2 • M1 & V1= initial molarity & volume • M2 & V2= initial molarity & volume • Moles of solute is same, regardless of amount of solvent • Ex 3: If 500 mL of 0.452 M NaOH is diluted to a volume of 1.00 L, what is the concentration of the resulting solution?

  14. A stock solution of 0.554 M HCl is kept in the laboratory and diluted whenever lower concentrations of hydrochloric acid are needed. • If 25.0 mL of the stock solution is placed in a 100.0 mL volumetric flask and water is added to the mark, what is the concentration of the resulting solution? • One liter of HCl is required with a concentration of 0.450 M. How much of the stock solution should be measured out in order to prepare the desired solution?

  15. Other Useful Concentrations • MOLAL CONCENTRATION – Advantage- molality (m) doesn’t vary with temperature, molarity (M) does. Ex. What is m for the solution made by dissolving 9.00 g of sodium chloride in 100.0 g of water? Moles of solute Molality (m) = Kilogram of solvent

  16. Other Useful Concentrations • MOLE FRACTION – • (Also independent of temperature.) • Has no units! • Sum of mole fractions is 1. (XA +XB = 1) Ex: 0.66 mol ethanol is mixed with 1.94 mol of water. What is A. Xethanol? B. Mole fraction of water? moles of A XA = total moles

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