solutions properties of water preparing solutions
TRANSCRIPT
Solute and Solvent
Solutions are homogeneous mixtures of two or more substances
Solute
The substance in the lesser amountSolvent
The substance in the greater amount
Nature of Solutes in Solutions
Spread evenly throughout the solution
Cannot be separated by filtration
Can be separated by evaporation
Not visible, solution appears transparent
May give a color to the solution
Types of Solutions
air O2 gas and N2 gas gas/gas
soda CO2 gas in water gas/liquid
seawater NaCl in water solid/liquid
brass copper and zinc solid/solid
(alloy)
Solute and Solvent
Identify the solute and the solvent.
A. brass: 20 g zinc + 50 g copper
solute = 1) zinc 2) copper
solvent = 1) zinc 2) copper
B. 100 g H2O + 5 g KCl
solute = 1) KCl 2) H2O
solvent = 1) KCl 2) H2O
Solution
A. brass: 20 g zinc + 50 g copper
solute = 1) zinc solvent = 2) copper
B. 100 g H2O + 5 g KCl
solute = 1) KCl
solvent = 2) H2O
Identifying Solutes
Identify the solute in each of the following solutions:
A. 2 g sugar (1) + 100 mL water (2)
B. 60.0 mL ethyl alcohol(1) and 30.0 mL
of methyl alcohol (2)
C. 55.0 mL water (1) and 1.50 g NaCl (2)
D. Air: 200 mL O2 (1) + 800 mL N2 (2)
Solution
Identify the solute in each of the following solutions:
A. 2 g sugar (1)
B. 30.0 mL of methyl alcohol (2)
C. 50 g NaCl (2)
D. 200 mL O2 (1)
“Like dissolves like”
A ____________ solvent such as water is
needed to dissolve polar solutes such as
sugar and ionic solutes such as NaCl.
A ___________solvent such as hexane
(C6H14) is needed to dissolve nonpolar
solutes such as oil or grease.
Is it soluble?
Which of the following solutes will dissolve in water? Why?
1) Na2SO4
2) gasoline
3) I2
4) HCl
Solution
Which of the following solutes will dissolve in water? Why?
1) Na2SO4 Yes, polar (ionic)
2) gasoline No, nonnpolar
3) I2 No, nonpolar
4) HCl Yes, Polar
Writing An Equation for a Solution
When NaCl(s) dissolves in water, the reaction can be written as
H2O
NaCl(s) Na+ (aq) + Cl- (aq)
solid separation of ions in water
Soluble because…..
Solid LiCl is added to some water. It dissolves because
A. The Li+ ions are attracted to the
1) oxygen atom(-) of water
2) hydrogen atom(+) of water
B. The Cl- ions are attracted to the
1) oxygen atom(-) of water
2) hydrogen atom(+) of water
Solution
Solid LiCl is added to some water. It dissolves because
A. The Li+ ions are attracted to the
1) oxygen atom(-) of water
B. The Cl- ions are attracted to the
2) hydrogen atom(+) of water
Properties of Solutions
1. homogeneous mixture if stirred during its formation
2. dissolved particles remain dissolved regardless of the time interval
3. a solution is clear and transparent 4. dissolved particles are extremely small
allowing for the solution to be filtered 5. considered to be a single phase
Types of Solutions 1. Gas/Gas 2. Liquid/Gas 3. Liquid/Liquid 4. Liquid/Solid 5. Solid/Solid
a. alloys b. amalgams
Terms to know: 1. solute - the substance being dissolved to form a
solution; usually in the lesser amount 2. solvent - the medium in which the solute is being
dissolved; usually in the greater amount 3. tincture - a solution in which the solvent is alcohol
(alcohol usually means ethanol or ethyl alcohol which has the formula, C2H5OH)
4. unsaturated - contains less solute that it is
capable of holding 5. saturated - contains the maximum amount of
solute that it is capable of holding 6. supersaturated - contains more solute that it is
capable of holding; metastable state which quickly returns to a saturated solution
7. solubility - the amount of a solute that can be
dissolved in a given amount of solvent 8. solubility curve - a plot which shows the amount
of solute that can be dissolved in a given amount of solvent and temperature
Factors affecting Solubility 1. Nature of the solute and solvent: the
expression, "Like dissolves like", describes this very well
2. Temperature - usually an increase in
temperature will increase the solubility of a solute in a given solvent. There are exceptions to this rule, but they are rare.
3. Pressure - affects only gaseous
solutions, those in which both the solute and solvent are gases and those in which one component is a gas and the other is a liquid
Factors Affecting the Rate of Solution 1. Size of the particles - in chemistry we
call this the surface area; the larger the surface area, the easier it is for a solute to dissolve
2. Stirring - more stirring increases the
contact between the solute and solvent and increases the rate of solution
3. Amount of solute already dissolved - as
the solute continues to dissolve, the solution will begin to approach the saturated state and the rate of dissolving will slow down
4. Temperature - for liquids and solids, an
increase will cause more solute to dissolve and to dissolve at a faster rate; the opposite is true for gas solutions