Transcript Solutions

Solutions & their Physical Properties
Solutions
Homogeneous mixtures are called solutions.
Solvent
is the component present in greatest
amount or determines the state of
solution exist
solute
is a component present in a lesser
quantity and it is said to be dissolved in
the solvent.
Solute
Solvent
Solution
example
Gas
Gas
Gas
Air
Gas
Liquid
Liquid
soda (CO2 in H2O)
Liquid
Liquid
Liquid
ethanol in water
Solid
Liquid
Liquid
Saline solution (NaCl in H2O)
Gas
Solid
Solid
H2 in Pd
Solid
Solid
Solid
14 karat gold (Ag in Au)
Solution Concentrations
Mass of solute
Percent by mass = ------------------------ x 100
Mass of solution
Volume of solute
Percent by volume = ------------------------- x 100
Volume of solution
Mass of solute
Mass / volume percent = --------------------- x 100 (gr/100ml)
Volume of solution
Solution Concentrations
Molarity
Number of moles of solute
= ----------------------------------------------Number of liters of solution
Number of moles of solute
Molality = -------------------------------------------------Number of kilograms of solvent
Moles of component i
Mole fraction = --------------------------------------------------------total moles of all solution components
Parts per million (ppm),
mg solute
1 ppm = -------------------kg solution
Parts Per Billion(ppb)
g solute
1 ppb = ----------------------kg solution
• question.
A solution has a density of 1.235g/ml and contains 90.0%
glycerol C3H8O3 and 10% H2O by mass. Determine
a- the molarity of C3H8O3
b- the molarity of H2O
c- mole fraction of C3H8O3
d- mole percent of H2O
e- the molality of H2O
Solubility
is the maximum amount of solute that dissolves in a given
quantity of solvent at a specific temperature to produce a
saturated solution
saturated
solution.
The solution in which no more solute can be dissolved is
said to be saturated solution.
Super saturated is a solution in which has higher amount of solute than
solution.
saturated solution
Unsaturated
solution
is a solution in which contain less amount of solute than
saturated solution
• Solubility of most of solids increase with temperature.
• Solubility of gases decrease with increased temperature
• Solubility of a gas increases as the gas pressure is increased.
• Types of solvent and solute is important,
like dissolves like, generally nonpolar substances are soluble in nonpolar
substances, polar solvents dissolves ionic and polar substances.
Solution Process
-a- Separation of solvent molecules from one another
Pure solvent → separated solvent molecules ∆ H > 0
-b- Separation of solute molecules from one another
Pure solute → separated solute molecules ∆ H > 0
-c- mixing solvent & solute molecules
separated solvent molecules
+
separated solute molecules
↔
solution
∆H < 0
∆ H solution = ∆ H a + ∆ H b + ∆ Hc
ideal solution
∆ H solution = ∆ H a + ∆ H b + ∆ Hc
Intermolecular Forces in Mixtures
**Like dissolves like**
Substances with similar intermolecular attractive forces tend to be
soluble in one another.
-Polar liquids tend to dissolve in polar solvents.
-Hydrogen bonding interaction between solute and solvent may
lead to high solubility. (In alcohols as the length of the carbon chain
increase, the solubility of alcohols in water decreases)
-The solubility of ionic compounds in water varies from one solid
to another. (strength of bonding forces within the solid)
- Nonpolar substances are soluble in nonpolar substances.
• Question: predict whether each of the following
subtances is more likely to dissolve in CCl4 or in H2O
C7H16 NaHCO3 HCl I2
Solubility & Temperature
• Solubility of most of solids increase with temperature.
• Solubility of gases decrease with increased temperature
crystallization
saturated
solution.
The solution in which no more solute can be dissolved is said to
be saturated solution.
Super saturated
solution.
is a solution in which has higher amount of solute than saturated
solution
Unsaturated
solution
is a solution in which contain less amount of solute than
saturated solution
• A solution is prepared by dissolving 95g NH4Cl in 200.0g H2O at 60°C,
What mass of NH4Cl will crystallize when the solution is cooled to 20 °C?
The solubility of NH4Cl
At 20 °C is 37gNH4Cl/100gH2O
At 60 °C is 56gNH4Cl/100gH2O
Solubility & Pressure
• Solubility of a gas increases with increasing pressure
Henry’s Law
C = k Pgas
C
= solubility of gas
k
= Henry’s Law constant
Pgas = is the partial pressure of gas above the solution
The solubility of pure nitrogen in blood at body temperature (37°C) and 1
atm is 6.2x10^-4M. If a diver breathes air (XN2= 0.78) at a depth where
the total pressure is 2.5atm, calculate the concentration of nitrogen in his
blood?
Vapor Pressures of Solutions
• Roault, 1880s.
– Dissolved solute lowers vapor pressure of solvent.
– The partial pressure exerted by solvent vapor above an
ideal solution is the product of the mole fraction of solvent
in the solution and the vapor pressure of the pure solvent at
a given temperature.
PA = A P°
A = Mole fraction
P° = vapor pressure of pure solvent
• Calculate the vapor pressure lowering caused by the addition
of 100g sucrose (C12H22O11) to 1000g of water. (water pressure
of pure water at 25°C is 23.8mmHg.
• A solution contains 102g of sugar (Mw=342.30g/mol) in 375g of
water. Calculate the vapor pressure lowering at 25°C (vp of pure
water 23.76mmHg at 25°C )
• The vapor pressures of pure benzene and pure toluen at 25°C
are 95.1 and 28.4mmHg respectively,when 1 mol benzene
mixed with 1 mol toluen calculate the total vapor presure of
the solution.
When a solution and a pure solvent (or two solution of different concentration) are
separated by a semipermeable membrane, solvent molecules pass through the
membrane in a process called osmosis.
The osmotic pressure is equal to the external pressure to prevent osmosis
Osmotic Pressure
When a solution and a pure solvent (or two solution of different concentration) are
separated by a semipermeable membrane, solvent molecules pass through the
membrane in a process called osmosis.
The osmotic pressure is equal to the external pressure to prevent osmosis
πV = nRT
n
π=
RT = M RT
V
For dilute solutions of electrolytes:
Reverse Osmosis - Desalination
• The average osmotic pressure of blood is 7.7atm at
25°C. What concentration of glucose will be isotonic with
blood.
• İsotonic solutions are the solutions which have same
osmotic pressure.
Freezing-Point Depression and Boiling Point Elevation
ΔTf = -Kf i m
m= molality
ΔTb = -Kb i m
i= van’t Hoff factor
van’t Hoff
i=
measured ΔTf
expected ΔTf
=
0.0361°C
0.0186°C
π = -i M RT
ΔTf = -i Kf m
ΔTb = -i Kb m
= 1.98
List the following solutions in order to their expected freezing
points
• 0.050m CaCl2
• 0.150m NaCl
• 0.100m HCl
• 0.050m HC2H3O2 (acetic acid)
• 0.100m C12H22O11
• Calculate the freezing point and the boiling point of a solution
of 100.0g ethyleneglicol (C2H6O2) in 900.0g H2O
• For water Kb=0.52°C/m Kf= 1.86 °C/m
• The osmotic pressure of 5g/L hemoglobin solution at 25°C is
0.0018atm, calculate the Mw of hemoglobin
• When 0.2 of a nonionic subtances dissolved in 50g puer water
the freezing point of this solution is found -0.22 °C, calculate
the Mw of the subtances
• To determine the molar mass of vasopressin, 10.00g of
vasopressin is dissolved in 50.00g of Naphthalene
(kf=6.94°C/m) the freezing point of the mixture is determined
to be 79.01°C, that of pure Naphthalene is 80.29°C. what is the
molar mass of vasopressin?
Naphthalene (Mw=128.2g/mol) is the active ingredient of moth balls. in
a solution prepared by mixing 25.0g Naphthalene with 0.750L of CS2
(d=1.263g/ml). Assume that volume remains 0.750L when the solution
is prepared.
•
what is the mass percent of Naphthalene in the solution
•
what is the concentration of Naphthalene in ppm
•
what is the density of the solution
•
what is the molarity of Naphthalene in the solution
•
what is the molality of Naphthalene in the solution
•
the vapor pressure of pure CS2 at 25°C is 358mmHg. Assume that the vapor
pressure exerted by Naphthalene at 25°C is negligible. What is the vapor pressure
of the solution at this temperature?
•
What is the osmotic pressure of the solution
•
The normal boiling point of CS2 is 46.13°C (Kb= 2.34°C/m) what is the normal
boiling point of the solution?