Embed Size (px)
Citation preview
7/13/2011 H. Esteban
Physical Properties of Solutions
7/13/2011 H. Esteban
A solution is a homogenous mixture of 2 or more substances
The solute is the substance present in the smaller amount
The solvent is the substance present in the larger amount
Determines the state of matter in which the solution exists
7/13/2011 H. Esteban
Types of Solutions according to components
7/13/2011 H. Esteban
Types of Solutions according to amount of solute present
saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.
7/13/2011 H. Esteban
Mass percent. (m/m)
Volume percent. (v/v)
Mass/volume percent. (m/v)
Isotonic saline is prepared by dissolving 0.9 g of NaCl in 100 mL of water and is
said to be:
0.9% NaCl (mass/volume)
Solution Concentrations
7/13/2011 H. Esteban
Solution Concentrations
10 % (v/v)8.03 % (m/m)7.89% (m/v)
•Mole fraction•Mole Percent•Molarity•Molality
7/13/2011 H. Esteban
Solution Concentrations
= Amount of component i (in moles)
Total amount of all components (in moles)
1 + 2 + 3 + …n = 1
Mole % i = i x 100%
7/13/2011 H. Esteban
Solution Concentrations
Molarity (M) = Amount of solute (in moles)Volume of solution (in liters)
Molality (m) = Amount of solute (in moles)
Mass of solvent (in kilograms)
7/13/2011 H. Esteban
Separation of Solute
must overcome IMF or ion-ion attractions in solute
requires energy, ENDOTHERMIC ( + DH)
Separation of Solvent
must overcome IMF of solvent particles
requires energy, ENDOTHERMIC (+ DH)
Interaction of Solute & Solvent
attractive bonds form between solute particles and solvent particles
“Solvation” or “Hydration” (where water = solvent)
releases energy, EXOTHERMIC (- DH)
7/13/2011H. Esteban
Intermolecular Forces and the Solution Process
DHsoln = DH1 + DH2 + DH3
7/13/2011 H. Esteban
Intermolecular Forces and the Solution Process
7/13/2011 H. Esteban
“like dissolves like”
Two substances with similar intermolecularforces are likely to be soluble in each other.
• non-polar molecules are soluble in non-polar solvents
CCl4 in C6H6
• polar molecules are soluble in polar solvents
C2H5OH in H2O
• ionic compounds are more soluble in polar solvents
NaCl in H2O or NH3 (l)12.2
7/13/2011 H. Esteban
Factors affecting solubility
1. Temperature
For Solids; solubility increases with increasing temperature (with some exception)
7/13/2011 H. Esteban
Factors affecting solubility
for Gases; solubility decreases with increasing temperature
7/13/2011 H. Esteban
Factors affecting solubility
2. Pressure
i) Solids/Liquids - Very little effect
Solids and Liquids are already close together, extra pressure will not increase solubility.
ii) Gas - Solubility increases with Pressure.
Increase pressure squeezes gas solute into solvent
7/13/2011 H. Esteban
The solubility of a gas in a liquid is proportional to the pressure of the gas over the solution.
c = kP
c = solubility of the gas (M)k = Henry’s Law ConstantP = partial pressure of gas
7/13/2011 H. Esteban
The solubility of pure N2 (g) at 25oC and 1.00 atmpressure is 6.8 x 10-4 mol/L. What is the solubility of N2 under atmospheric conditions if the partial
pressure of N2 is 0.78 atm?
Step 1: Use the first set of data to find “k” for N2 at 25°C
Step 2: Use this constant to find the solubility (concentration) when P is
0.78 atm:
44 16.8 10
6.8 101.00
c x Mk x M atm
P atm
4 1 4(6.8 10 )(0.78 ) 5.3 10c kP x M atm atm x M
7/13/2011 H. Esteban
Exercises:
1. A 11.3 ml sample of methanol ( CH3OH d = 0.793g/ml) is dissolved in enough water to produce 75.0ml of a solution with a density of 0.980 g/ml. What is the solution concentration expressed as (a) mole fraction of H2O; (b) molarity; (c) molality?
2. Laboratory ammonia is 14.8 NH3 (aq) with a density of 0.8980 g/ml. What is XNH3 in this solution?
3. A 10.00% by mass aqueous solution of sucrose C12H22O11, has a density of 1.040 g/ml. What is (a) the molarity; (b) the molality, and (c) the mole fraction of C12H22O11 in the solution?
7/13/2011 H. Esteban
4. In which solvent is I2 likely to be more soluble, water or CCl4? Explain.
5. Henry’s Law. At 0 degree Celsius and an O2 pressure of 1.00 atm, the aqueous solubility of O2(g) is 48.9 ml O2 per Liter. What is the molarity of O2 in a saturated water solution when the O2 is under its normal partial pressure in air , 0.2095 atm?
