Properties of Solutions Chapter 13

Vocabulary: A Review A homogeneous mixture. Solution The item dissolved. What the solute is dissolved in. Solution Solute Solvent

gas gas gas air, natural gas liquid gas liquid carbonated water Types of Solutions State of solution State of solute State of solvent example gas gas gas air, natural gas liquid gas liquid carbonated water solid gas solid hydrogen in platinum liquid liquid liquid alcohol and water liquid solid liquid sea water solid solid solid metal alloys

Solution Composition Relatively little amount solute Dilute Relatively large amount solute Dilute Concentrated Molarity Mass percent or weight percent Mole fraction Molality

Molarity versus Molality Molarity: Moles solute/Liters solution It is expressed as [solute] = M Liquids change density with change in temperature. Therefore: Molarity is not constant with temperature changes

Molarity versus Molality Molality: moles solute/kg solvent The weight of the liquid is constant with changes in temperature.

Question: A solution is prepared by mixing 1.00 gram of ethanol (C2H5OH) with 100 gram water to give a final volume of 101 mL. Calculate the molarity, mass percent, mole fraction and molality of ethanol in this solution. Molar mass of ethanol is 46.07 g/mol. 0.0217 mol ethanol. Volume 0.101 L Molarity 0.215 M Mass percent: 0.990 % ethanol. (1g/101g)*100 Mole fraction: 0.00389 0.0217 mol 5.56 mol H2O + 0.0217 mol etOH Molality: 0.217 m 0.0217 mol/0.1 kg

Normality A concentration measure. Defined as the number of equivalents per liter. For acids: The [H+] per liter 1 M HCL is 1 N HCL 1 M H2SO4 is 2 N H2SO4 For redox: The [e-] per liter or electron consumption per liter.

The Molar Mass, Equivalent Mass, Molarity and Normality for some acids and bases Acid/base MM Equ M M vs N HCL 36.5 36.5 1 M = 1 N H2SO4 98 98/2=49 1 M = 2 N NaOH 40 40 1 M = 1 N Ca(OH)2 74 74/2=37 1 M = 2 N

Heat of solution formation Why are some things soluble and not others? Why does “like dissolve in like”? Why do solution behave as they do? Demo?

step what happens                 DH 1 solute particles separate into their individual components + 2 Overcoming the IMF’s of the solvent particles make "space" or “expanding” for solute 3 solute and solvent particles "interact“ to form solution -

Enthalpy heat of solution The enthalpy of the heat of a solution is the sum of the enthalpy of the three steps. ΔH solu = ΔH 1 + ΔH 2 + ΔH 3

Which picture best describes a solution of HCl?

Probability Why is NaCl so soluble in water if it actually takes a little energy to form a solution (4 kJ/mol)? The mixed state is more likely to occur as there are many more ways of placing the mixed state ions in water than the one unmixed state. Think Entropy: ΔS.

saturated: no more solute will dissolve     unsaturated: able to dissolve more solute     super-saturated: contains more solute than will dissolve under ordinary conditions