Solutions Flashcards
Chapter 6
What is:
Brass?
A mixture of copper and zinc
What is:
German silver?
A mixture of copper, zinc and nickel
What is:
Bronze?
A mixture of copper and tin
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1ppm of flouride in water —-
—— prevents tooth decay
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1.5 ppm of flouride in water—–
——- mottles teeth
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Any concentration of flouride in water above that—–
—— is commonly used as rat poison
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A solution consists of——-
———- a solute and a solvent
Solute (present in lesser amounts)
Solvent (present in larger amounts)
What is:
A binary solution?
A binary solution contains only 2 components
List:
Types of binary solutions:
- Gaseous solutions
- Liquid solutions
- Solid solutions
What is:
Mass percentage?
(mass of a substance/ total mass of a solution ) *100
Commercial bleaching solutions: 3.62% of sodium hypochlorite in water.
What is:
Volume percentage?
(volume of a substance/total mass of a solution) *100
35% solution of ethylene glycol (antifreeze) used to cool engines
What is:
Mass/volume percentage?
(Mass of a substance/volume of a solution) *100
What is:
Parts per million (ppm)?
(no. of parts (in mass/volume) of the component / total no. of parts (in mass/volume) of all components) *10^6
What is:
Mole fraction?
(no. of moles of the component/total no. of moles of all components)
Xa + Xb = 1
What is:
Molarity?
no. of moles of the solute/ volume of the solution (L)
Also: percent x density x 10 / M2
What is:
Molality?
no. of moles of solute/ mass of the solvent (Kg)
What is:
Solubility?
The maximum amount of substance that can be dissolved in a specific amount of solvent at a particular temperature.
It depends on: the nature of the substances, temp. and pressure
What is:
‘Like dissolved like’?
A solute will only dissolve in a solvent if the intermolecular forces in the two are similar.
What is:
Dissolution?
When a solid solvent is added to a solute, some of it dissolves and the conc. of the solution increases.
What is:
Crystallisation?
Some solute particles in the solution collide with the solid solute and get seperated out of the sollution.
What is:
Saturation?
A solution in which no more solute can be dissolved at the same temp. and pressure.
Effect of:
Temp. of the solubility of a solid in liquid?
(If endothermic) Increase in temp. = increase in solubility
(If exothermic) Increase in temp. = decrease in solubility
Effect of:
Pressure on the solubility of solids in gases?
Pressure does not have any effect.
Effect of:
Temp. on the solubility of gases in liquids?
(is an exothermic process) as temp. increases, the solubility decreases.
Effect of:
Pressure of the solubility of gases in liquid?
As pressure increases, solubility increases
State:
Henry’s law:
( for gases in liquids)
The vap. pressure of the gas above the soltuion ∝ the mole fraction of gas in the solution.
P ∝ X
P = Kh X
Pressure at STP = 1 bar = 0.987 atm.
List:
How does Kh vary with temp., solubility and pressure?
As temp increases, Kh increases
As solubility increases, Kh decreases
As pressure increases, Kh decreases
List:
Medical conditions associated with the solubility of gases in liquids:
- Bends
- Anoxia
State:
Raoult’s law (for liq. in liq. solution) :
(for a solution of 2 volatile liquids), the partial pressure of each component above the solution is ∝ the mole fraction of that component in the solution.
p1 ∝ X1
p2 ∝ X2
What is:
Formula for total pressure?
P (total) = p1 + p2 = p1o + X2 (p2o - p1o)
State:
Raoult’s law ( for solid in liq. solutions)
(for a solution of a solid in a volatile liquid), the partial pressure of the liquid vapour ∝ its mole fraction in the solution
p1∝ X1
p1 = p1o X1
What is:
An ideal solution?
A solution that obeys Raoult’s law over the entire range of concentrations.
ΔH mix = 0
ΔV mix = 0
Ptotal = P1 + P2
List:
Examples of ideal solutions:
- n hexane and n heptane
- Bromoethane and chloroethane
- Benzene and Toulene
What is:
A non-ideal solution?
A solution that does not follow Raoutl’s law for the entire range of concentration.
Ptotal is greater than/lesser than P1 + P2
List:
Types of non-ideal behaviour:
- Positive deviation:
ΔH mix > 0
ΔV mix > 0
Ptotal > P1 + P2 - Negative deviation:
ΔH mix < 0
ΔV mix < 0
Ptotal < P1 + P2
List:
Examples of positive deviation:
- ethanol and acetone
- cyclohexane and ethanol
- carbon disulphide and acetone
List:
Examples of negative deviation:
- chloroform and acetone
- phenol and aniline
- aniline and acetone
What is:
An azeotrope?
Are solutions with the same concentration in the liquid and vapour phase. They boil at constant temp. and cannot be seperated by distillation.
List:
Types of azeotropes:
- Minimum boiling azeotrope (show large +ve deviation from Raoult’s law) ex// 95% ethanol in water by volume
- Maximum boiling azeotrope (show large -ve deviation from Raoult’s law) ex// 68% nitric acid and 32% water by mass
What is:
A colligative property?
A property that depends only on the no. of solute particles relative to the total no. of particles in the solution.
List:
Colligative properties:
- Relative lowering of vapour pressure
- Boiling point
- Depression of freezing point
- Osmosis and osmotic pressure
What is:
Boiling point?
The temp. at which the vapour pressure of the volatile liquid = the atmospheric pressure
What is:
Freezing point?
Freezing point of the pure solvent = temp. at which the vap. pressure of the liq. solvent = the vap. pressure of the freezing solvent.
Freezing point of the solution = temp. at which the vap. pressure of the solution ( liquid solvent + solute) = the vap. pressure of the solid solvent.
What is:
Osmosis?
Flow of solvent from high conc. —> low conc.
or solvent —-> solution
Dilute solution —–> conc. solution
What is:
Osmotic pressure?
It is the extra pressure that has to be applied on the solution side to stop the slow of the solvent from the pure solvent to the solution across the semi-permeable membrane.
List:
Examples of SPM:
- Pig’s bladder
- Cellophane
List:
Types of solutions based on conc:
- Isotonic ( same conc. no osmosis)
- Hypotonic ( low conc. (less than 0.9%) of solute, cell swells)
- Hypertonic ( high conc. of solute, cell shrinks)
What is:
Reverse osmosis?
Pressure (greater than osmotic pressure) is applied to the solution side to force the solvent to move fro the solution side to the solvent side through an SPM.
SPM used: cellulose acetate
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Water boils at:
100 celcius or 373.15 K
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Water freezes at:
0 celcius or 273.15 k
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Kf for water:
1.86 K/mol/kg
