Definition: SOLUTIONDefinition: SOLUTION
A system in which one or more A system in which one or more substances are homogenously mixed substances are homogenously mixed or dissolved in another substance.or dissolved in another substance.
In other words: two chemicals mixed In other words: two chemicals mixed together completely. together completely.
Can result in a solid, liquid, or gasCan result in a solid, liquid, or gas
What are some What are some examples?examples?
ShampooShampoo Soft drinksSoft drinks Air Air GasolineGasoline steelsteel
What do you need to make What do you need to make a solution?a solution?
Example: Kool-aid, basically sugar waterExample: Kool-aid, basically sugar water
1) solute—part being dissolved (sugar)1) solute—part being dissolved (sugar) 2) solvent—part doing dissolving (water)2) solvent—part doing dissolving (water)
+ =
A True SolutionA True Solution
5 Properties of True Solutions5 Properties of True Solutions
1) mixture is homogenous and the 1) mixture is homogenous and the ratios of solvent to solute can be ratios of solvent to solute can be varied. varied.
In Kool-aid example, more or less sugar In Kool-aid example, more or less sugar could be added to make the solution could be added to make the solution more or less concentrated.more or less concentrated.
A True SolutionA True Solution
PropertiesProperties
2) The dissolved solute is molecular 2) The dissolved solute is molecular or ionic in size.or ionic in size.
The sugar in the packet dissolves into The sugar in the packet dissolves into separate sugar moleculesseparate sugar molecules
A True SolutionA True Solution
PropertiesProperties
3) It is either colorless 3) It is either colorless
or transparent (not cloudy)or transparent (not cloudy)
A True SolutionA True Solution PropertiesProperties
4) The solute is uniformly distributed 4) The solute is uniformly distributed and doesn’t settle out over time.and doesn’t settle out over time. After an hour, the solution should still After an hour, the solution should still
look the same. No chunks at the look the same. No chunks at the bottom or top…think of hot chocolate bottom or top…think of hot chocolate when it sits for a whilewhen it sits for a while
A True SolutionA True Solution
PropertiesProperties
5) The solute can be separated from 5) The solute can be separated from the solvent by physical means the solvent by physical means (evaporation, filtration, boiling, etc)(evaporation, filtration, boiling, etc)
Recall the first lab where we boiled salt Recall the first lab where we boiled salt water, after the water evaporated, the water, after the water evaporated, the salt was left at the bottom. salt was left at the bottom.
Dissolving Dissolving
How do substances dissolve?How do substances dissolve?
DiffusionDiffusion
Molecules travel from areas of high Molecules travel from areas of high concentration to areas of low concentration to areas of low concentration.concentration.
SolubilitySolubility describes how likely one describes how likely one substance will dissolve in another.substance will dissolve in another.
SolubilitySolubility
AmountAmount of solute that can dissolve of solute that can dissolve in the solvent.in the solvent.
Solubility varies with temperature.Solubility varies with temperature.
4 ways to make a solute 4 ways to make a solute dissolve faster?dissolve faster?
(1)INCREASE THE TEMPERATURE(1)INCREASE THE TEMPERATURE for liquids, this causes the solvent for liquids, this causes the solvent
molecules to move faster and bump into the molecules to move faster and bump into the solute particles more often and harder, solute particles more often and harder, breaking them apart faster.breaking them apart faster.
(2) AGITATION OR STIRRING(2) AGITATION OR STIRRING this physically helps the solute particles this physically helps the solute particles
diffuse by distributing them to all parts of diffuse by distributing them to all parts of the solvent.the solvent.
(3)BREAK IT DOWN(3)BREAK IT DOWN The smaller the particle, the faster it The smaller the particle, the faster it
dissolvesdissolves
How can I make a solute How can I make a solute dissolve faster?dissolve faster?
(4) CONCENTRATION(4) CONCENTRATION The closer you get to the saturation The closer you get to the saturation
point, the slower the dissolving occurspoint, the slower the dissolving occurs The solute dissolves quickly at first The solute dissolves quickly at first
because there is a lot of area to dissolve because there is a lot of area to dissolve intointo
As more of the solute dissolves, the As more of the solute dissolves, the area shrinks and dissolving slows down.area shrinks and dissolving slows down.
What Affects a Substance’s What Affects a Substance’s Solubility? Solubility?
Question:Question:
When making Jell-o, why do the When making Jell-o, why do the directions tell you to pour the packet directions tell you to pour the packet into hot water and then cool it?into hot water and then cool it?
Why can’t you just pour it in Why can’t you just pour it in cold water and then drink it right cold water and then drink it right away?away?
What 3 factors affect the What 3 factors affect the Solubility of substances?Solubility of substances?
(1) Temperature(1) Temperature For For LIQUIDSLIQUIDS::
More solute can be dissolved if you More solute can be dissolved if you use warm solvents.use warm solvents.
Why?Why? The KMT of courseThe KMT of course
Which one would dissolve Which one would dissolve more salt?more salt?
100 C 50 C
How much more would the first cup dissolve?
Solubility CurvesSolubility Curves
Can use a graph to represent Can use a graph to represent solubilitysolubility
Y-axis = grams of solute per 100g Y-axis = grams of solute per 100g HH22OO
X-axis = temperatureX-axis = temperature Different substances will have different Different substances will have different
curves on the graph.curves on the graph.
What’s happening with HCl, NH3, and SO2 (dotted lines)
Solubility of GasesSolubility of Gases
The solubility of gases decreases The solubility of gases decreases with increasing temperatures.with increasing temperatures.
Can you think of a situation where Can you think of a situation where this principle is illustrated? (hint: this principle is illustrated? (hint: many of you have one at lunch time)many of you have one at lunch time)
SODASODA
SODASODA
Cold soda is more fizzy because Cold soda is more fizzy because more gas is dissolved in the soda.more gas is dissolved in the soda.
Why does soda become flat as it Why does soda become flat as it warms to room temperature? warms to room temperature? (remember the KMT)(remember the KMT) As the soda becomes warm, the gas As the soda becomes warm, the gas
molecules begin to move faster and molecules begin to move faster and evaporate out of the soda.evaporate out of the soda.
(2) Solubility & Pressure(2) Solubility & Pressure
Changes in pressure have the largest Changes in pressure have the largest effect on gases dissolved in liquids.effect on gases dissolved in liquids.
Pressure and solubility vary directly.Pressure and solubility vary directly.
As the pressure increases, the As the pressure increases, the solubility increases.solubility increases.
Back to the SodaBack to the Soda
Why does a can of soda fizz when it’s Why does a can of soda fizz when it’s opened?opened?
Canned at high pressures.Canned at high pressures. When it’s opened, the pressure inside is When it’s opened, the pressure inside is
reduced to the atmospheric pressure, reduced to the atmospheric pressure, and the excess dissolved COand the excess dissolved CO22 bubbles bubbles out of the sol’n.out of the sol’n.
(3) The Nature of the (3) The Nature of the Solute and the SolventSolute and the Solvent
Explain why water and oil do not Explain why water and oil do not mix?mix?
Like dissolves likeLike dissolves like Polar substances dissolve in other Polar substances dissolve in other
polar substances and nonpolar polar substances and nonpolar dissolve in nonpolar.dissolve in nonpolar.
Oil is nonpolar and water is polar.Oil is nonpolar and water is polar.
Nonpolar vs. PolarNonpolar vs. Polar
When nonpolar substances dissolve When nonpolar substances dissolve in one another, they simply mix.in one another, they simply mix.
When polar substances dissolve, When polar substances dissolve, electrical reactions pull apart the electrical reactions pull apart the molecules.molecules.
Saturated, Unsaturated, & Saturated, Unsaturated, & Supersaturated Sol’nsSupersaturated Sol’ns
SATURATEDSATURATED Holds the maximum amount of solute in the Holds the maximum amount of solute in the
dissolved state dissolved state No more solute can be added and still No more solute can be added and still
dissolve.dissolve. UNSATURATEDUNSATURATED
More solute could be added and still More solute could be added and still dissolve.dissolve.
SUPERSATURATEDSUPERSATURATED Holds more solute than the max.Holds more solute than the max. Very unstable and have to be prepared in a Very unstable and have to be prepared in a
special way. special way.
Supersaturated SolutionsSupersaturated Solutions
Hand/foot warmer packs used for Hand/foot warmer packs used for cold weather are examples.cold weather are examples.
Activated when they are crushedActivated when they are crushed The heat generated is a result of the The heat generated is a result of the
supersaturated solution coming out supersaturated solution coming out of supersaturation. This reaction is of supersaturation. This reaction is exothermicexothermic..
Cold packs work the same way but Cold packs work the same way but are are endothermicendothermic reactions. reactions.
Will a solution made by adding 2.5g of Will a solution made by adding 2.5g of CuSOCuSO44 to 10g of H to 10g of H22O be saturated or O be saturated or unsaturated at 20°C?unsaturated at 20°C? Use the curve on slidesUse the curve on slides Find the solubility of CuSOFind the solubility of CuSO4 4 at 20°at 20°
It is 21g per 100g HIt is 21g per 100g H22OO
This is equivalent to 2.1g CuSOThis is equivalent to 2.1g CuSO44 per 10g per 10g HH22O O
Since 2.5 is greater than 2.1, the sol’n will Since 2.5 is greater than 2.1, the sol’n will be saturated. How much will be be saturated. How much will be undissolved?undissolved?
.4g .4g
You TryYou Try
Will a sol’n made by adding 9.0g Will a sol’n made by adding 9.0g NHNH44Cl to 20g of HCl to 20g of H22O be saturated or O be saturated or unsaturated at 50°C?unsaturated at 50°C?
unsaturatedunsaturated
Solution ConcentrationSolution Concentration
Equations to learnEquations to learn (1) Molarity(1) Molarity (2) Dilution (2) Dilution
MolarityMolarity Molarity describes a solution’s concentration Molarity describes a solution’s concentration
by telling you how many moles of solute exist by telling you how many moles of solute exist in one liter of solution. (symbol is a capital in one liter of solution. (symbol is a capital MM))
M = molesM = moles LLA 6 M HCl solution contains 6 moles of HCl for A 6 M HCl solution contains 6 moles of HCl for
every Liter of solution.every Liter of solution.
What does a 5.7 M solution contain?What does a 5.7 M solution contain?
5.7 moles of HCl for every Liter of solution.5.7 moles of HCl for every Liter of solution.
DilutionsDilutions Sometimes the available solution might be to Sometimes the available solution might be to
concentrated for our purposes; therefore we concentrated for our purposes; therefore we must must dilutedilute the solution. the solution.
In other words, we reduce the concentration In other words, we reduce the concentration of our solution. To find out how much of our solution. To find out how much solvent we must add to reduce the solvent we must add to reduce the concentration, we use the following formula:concentration, we use the following formula:
MM11VV11 = M = M22VV2 2 where where M=molarityM=molarity
DilutionDilution
100mL water
6 moles NaCl
200mL water
6 moles NaCl
The moles are the same in The moles are the same in each glasseach glass
Because they contain the same Because they contain the same amount of moles, we can use:amount of moles, we can use:
MM11VV11 = M = M22VV2 2 M=molarityM=molarity
oror CC11VV11 = C = C22VV2 2 C=concentration C=concentration
ExamplesExamples
Calculate the molarity of a solution Calculate the molarity of a solution prepared by diluting 125 mL of prepared by diluting 125 mL of 0.400 M K0.400 M K22CrCr22OO77 with 875 mL of with 875 mL of water.water.
(125)(.400) = (1000) M(125)(.400) = (1000) M22
.05 M .05 M
