Solutions.

Solutions

Section 1A Types of Mixtures

Called Solutions There are TWO types of Mixtures:
Heterogeneous mixtures have parts with different makeup and Homogeneous mixtures uniformly mixed mixtures Called Solutions

Usually have visibly different phases
1) Heterogeneous mixtures have parts with different makeup Usually have visibly different phases The water is liquid Remember the yellow PbI2 ? Lead Iodide precipitate at the molecular level. The yellow stuff is solid

Many heterogeneous mixtures are SUSPENSIONS with larger insoluble “specks” suspended in another substance The water is liquid Remember the yellow PbI2 ? Lead Iodide precipitate at the molecular level. The yellow stuff is solid

Solutions are transparent
Suspensions: The specks are “visible” to the naked eye Solutions are transparent (no tyndall effect) (they appears cloudy – called the “Tyndall” effect) Tyndall effect: Can you see a beam of light in the left beaker? That’s the tyndall effect.

Suspensions: Specks will settle out So suspensions can be filtered
The yellow solid will get caught in the filter Anything still dissolved the solution passes through into the beaker below

Fog: The droplets of water suspended in the air scatter the light
Tyndall Effect Again! Fog is a liquid suspended in the gaseous air!

2. Homogeneous mixtures (uniform makeup throughout)
Are ”Solutions” mixtures of individual particles (molecules, ions, etc.) of one substance dispersed in another substance CuSO4(aq)

NaCl(aq) When NaCl dissolves in water
Ions disperse and mix uniformly with water

Solutions are made of Two parts: the SOLVENT: is the dissolving substance its usually a liquid its usually water called “aqueous” (aq) CuSO4(aq) Water is the solvent in this aqueous solution of copper sulfate

Solutions are made of Two parts: And the SOLUTE: (sol·ute ˈsälyo͞ot/) is the dissolved substance its usually a solid CuSO4(aq) …and Copper sulfate is the solute.

Sugar is the solute Water is the solvent. Other soluble solutes are also dissolved of course, making it coffee.

Notice how the Na+ and Cl- ions are dispersed throughout the water?
Salt water That’s why it’s a “homogeneous” mixture

Homogeneous Characteristics: > dissolved particles won't settle out > are clear and transparent (may be colored)

Homogeneous Characteristics: > Solutions can’t be separated by a filter
suspension During a filtration, the solution runs through the filter and collects in the beaker below solution

Examples: Salt-water -NaCl (aq) Seltzer -CO2 gas dissolved in water
Notice that its clear and transparent solution?

Examples: Salt-water -NaCl (aq) Seltzer -CO2 gas dissolved in water
Once the bubbles appear in soda it becomes a suspension. 

Seltzer -CO2 gas dissolved in water
Examples: Salt-water -NaCl (aq) Seltzer -CO2 gas dissolved in water Metal alloys- ex: brass (Cu and Zn mixture) A brass pipe “elbow”

Try these: HDYK

The dissolving process
Section 1B The dissolving process

The Dissolving process:
1- The solvent (H2O) strikes a solute particle and pulls it into the solution

2- Each ion becomes surrounded by water molecules (they become “hydrated”)

H--- O Na+ O---H O---H Cl- H---O | | | | + H H + H H Notice: The positive aligns to the negative and vice versa

Recall that due to their shape, water molecules are polar?

Try this:

Electrolytes Electrolytes are ionic compounds (salts) that break into ions when dissolved in water allowing them to conduct electricity A balanced equation shows the “dissociation” that occurs

Electrolytes Write the equation showing the dissociation of table salt NaCl into its aqueous ions:

Electrolytes Non- electrolytes – molecules stay together when dissolved in water – don’t conduct Ex: sucrose: C12H22O11 (s)  C12H22O11 (aq) Heres the equation for table sugar dissolving in water Molecules don’t break into ions when dissolved.

Electrolytes the molecules separate but remain neutral even when dissolved. No charged ions, no conductivity!

Electrolytes Weak electrolytes – a few molecules break apart, most stay together- fair electrical conductors Ex: weak acids: acetic acid HC2H3O2  H+ + C2H3O- Most stay as neutral molecules while a few split into ions

Try these: HDYK

Try this: Illustrate:

Problems 1. Identify the solvent and the solute in vinegar, a dilute aqueous solution of acetic acid. 2. What is the basis for distinguishing among solutions, and suspensions? 3. Suppose an aqueous solution contains both sugar and salt. Can you separate either of these solutes from the water by filtration? Explain. 4. Describe how an ionic compound dissolves in water. 5. Write an equation showing how calcium chloride dissociates in water. 6. Distinguish between an electrolyte and a non-electrolyte. 7. What is the main distinction between an aqueous solution of a strong electrolyte and an aqueous solution of a weak electrolyte?

Section 2A Solubility

ex: “sugar is soluble in water; chalk is not”
Solubility is the ability of one substance to dissolve in another substance ex: “sugar is soluble in water; chalk is not” Sugar is very soluble in water due to hydrogen bonding

Lead iodide is not soluble
(that’s why its precipitating)

Oil and water are not miscible
…not soluble when together

We say… "LIKES DISSOLVE LIKES“
Solubility Factors We say… "LIKES DISSOLVE LIKES“ Polar solvents will dissolve polar solutes and ionic compounds Polar: NH3, HCl, NaCl (salts); dissolve easily in water

Solubility Factors We say… "LIKES DISSOLVE LIKES“ Polar solvents will dissolve polar solutes and ionic compounds Ionic salts like NaCl dissolve easily in water

Solubility Factors We say… "LIKES DISSOLVE LIKES“ Notice: both NH3 and H2O are polar? Likes dissolve likes.

Solubility Factors We say… "LIKES DISSOLVE LIKES“ Nonpolar: O2 CO2 (nonpolar) do not dissolve easily in water CO2 un-dissolves unless kept under pressure

Purple Iodine crystals were stirred into a beaker of oil and water. Which layer dissolved the iodine? Why? I2 is nonpolar Oil is nonpolar Water is polar

HDYK Try these:

Solubility factors (cont.)
Temperature - Solids: greater temperature, greater solubility (example: washing clothes)

Solubility factors (cont.) Temperature
Gases: greater temperature, lesser solubility Example: air bubbles escaping from water as its heated

Gases only - greater pressure = greater solubility
Example: Opening a soda bottle What happens to the gas pressure when the bottle is opened? What happens to the solubility of CO2 gas in the water, when the bottle is opened?

RATE OF SOLUTION speed of dissolving (is not the same as solubility)
Be Careful! RATE OF SOLUTION speed of dissolving (is not the same as solubility) Factors: Size of Particles (surface area) / Stirring / Temperature / Amount already dissolved Dissolving a bullion cube is slow due to surface area How could you speed up dissolving? Crush it to increase surfaces exposed to hot water.

RATE OF SOLUTION speed of dissolving (is not the same as solubility)
Be Careful! RATE OF SOLUTION speed of dissolving (is not the same as solubility) Factors: Size of Particles (surface area) / Stirring / Temperature / Amount already dissolved Stirring speeds dissolving, not solubility Without stirring, the sugar may not dissolve by the time you drink the tea.

Try these solubility factor questions:

16 23 31 42

Solubility tables Solubility curves
Section 2B Solubility tables Solubility curves

Review of SOLUBILITY TABLES: (Table F):
Table showing solubility of ionic compounds in water Soluble vs. Insoluble* ions and exceptions *Note: Ions, which are insoluble, may dissolve to a very small extent Used to predict products and extent of double replacement reactions These ions are soluble except when bonded to these These ions are not soluble except when bonded to these

Which chlorides are least soluble?
Write their formulas: Write the formula for any soluble carbonate compound:

HDYK Try these:

SOLUBILITY CURVES: graphs showing solubility of a substance over a range of temperatures.
Water temperature X At low temperature, relatively small samples can be dissolved

X Water temperature X X X X As water temperature increases, a greater quantity can be dissolved

Points on the line represent greatest amount of solute which can be dissolved in each 100 mL of water at a particular temperature At 30 oC one can dissolve about 50 grams of KNO3 in 100 grams of water At 100 oC one can dissolve about 50 grams 100 grams 150 grams 200 grams 260 grams of KNO3

Notice as solution temperature increases, Solubility increases
SOLUBILITY CURVES: graphs showing solubility of a substance over a range of temperatures. Notice as solution temperature increases, Solubility increases (More solute can be dissolved)

What mass of KNO3 will dissolve in 100 grams of water at 1000C?
250 grams of KNO3 Can dissolve in 100 g of water What mass of KNO3 will dissolve in 100 grams of water at 1000C? 250 grams of KNO3

In 200 grams of water? 250 g KNO3 = X g KNO3 100 g H2O 200 g H2O
At 100 0C 250 grams of KNO3 Can dissolve in 100 g of water In 200 grams of water? 250 g KNO3 = X g KNO3 100 g H2O g H2O 500 grams of KNO3

In 200 grams of water? Twice as much? Go figure. At 100 0C
250 grams of KNO3 Can dissolve in 100 g of water In 200 grams of water? Twice as much? Go figure. 500 grams of KNO3

Types of Solutions At 100 0C 250 grams of KNO3 Is required to saturate
A Saturated Solution is a solution holding the maximum quantity of solute at a given temperature. (Points on the curve) At 100 0C 250 grams of KNO3 Is required to saturate 100 mL Of water

Types of Solutions Unsaturated solution: holding less than the Maximum quantity of solute at a given temperature (Points below the curve) At 100 0C 100 grams of KNO3 Dissolved is an Unsaturated solution It can still hold 150 grams more!

Types of Solutions Super–saturated: Holding more than the maximum at a given temperature (Points above the curve) At 40 0C 250 grams of KNO3 Dissolved would be a supersaturatedsolution

Types of solutions Supersaturated Saturated unsaturated

How is a supersaturated solution made?
A Hot saturated solution cools (but nothing precipitates)

How is a supersaturated solution made?
2) Adding a small crystal starts the precipitation (the excess comes out)

3) Solution is back to saturated
How is a supersaturated solution made? 3) Solution is back to saturated

Do these: 1. How many grams of KNO3 will dissolve in 100 grams of water at 300C? 2. Is a solution with 100 grams of NaNO3 Dissolved In 100 grams of water at 500C Saturated? OR Unsaturated? 3. List one solute which is most likely a gas. How do you know? 4. 30 grams KCl is dissolved In 100 grams of water at 800C. How much additional solute must be added to saturate the solution? grams of water saturated with NH4Cl at 900C is cooled to 700C. How much solute will precipitate out?

Types of solutions Relative to how concentrated
Concentrated -relatively large amount of solute in a given volume of water (high on table) Unsaturated solution of 130 grams Of KI in 100 g of water at 300C More solute than water! Orange juice “concentrate A lot of orange in a little water!

Types of solutions Relative to how concentrated
Concentrated -relatively large amount of solute in a given volume of water (high on table) Vs. Dilute -relatively small amount of solute in a given volume of water (low on table) Saturated solution of 12 grams of KClO3 In 100 g of water at 300C

What must be done to the concentrate to prepare the juice?
Dilute it with water!

Try these:

Problems 1. What is the significance of the statement” like dissolves like”? What does “like” refer to? 2. Which of the following substances dissolve to a significant extent in water? Explain your answer in terms of polarity and compound type. a. CH4 d. MgSO4 b. KCl e. sucrose c. CO f. NH3 3. Why is water an excellent solvent for most ionic compounds and polar covalent molecules but not for nonpolar compounds? 4. How is the solubility of most gases affected by changes in temperature and gas pressure? 5. Name three factors that influence the rate at which a solute dissolves in a solvent.

Problems 6. Use reference table to make a general statement that relates a change in solubility of a solid to a change in temperature. 7. In your own words define… Solubility – Saturated solution- Unsaturated solution- 8. What could you do to change a. a saturated solution to an unsaturated solution? b. an unsaturated solution to a saturated solution? 9. What mass of AgNO3 can be dissolved in 250 g of water at 20oC (show “work”) 10. How many grams of NaNO3 will precipitate if a saturated solution of NaNO3 in 200 g H2O at 50oC is cooled to 200C? ______. (show work).

Quantifying concentration
Section 3A Quantifying concentration

Expressing Concentration
Percent composition Parts of solute x 100 Total Parts of solution Ex: 2% = grams of fat milk grams of milk

Molarity

Which of the three is most concentrated?
1 0.500 2 1.00 In each case the ratio of moles of chemical to volume of solution is the same 1 mole dissolved in 500 mL of solution 2 moles dissolved in 1000 mL of solution Each has 2 moles of chemical per 1000 mL (liter) of solution We say that each is 2 “molar” concentration - abbreviated “2 M” This means 2 moles of solute dissolved per liter of solution. 0.5 0.250 0.5 mol in 250 mL

Which of the three is most concentrated?
2 mol = 5 M 0.4 L 3 mole dissolved in 900 mL of solution 2 mole dissolved in 400 mL of solution 3 mol = 3.3 M 0.9 L Has the least chemical, but even less volume! 1 mol = 10 M 0.1 L 1 mole dissolved in 100 mL of solution

Expressing Concentration:
Molarity – moles of solute in every 1 liter of solution Molarity = #moles solute # liters solution Moles per liter mol/L Ex: What is the molarity of a solution with 4 moles of solute dissolved in 2 liters of solution? Ex: How many moles of solute are dissolved in 0.5 liters of a 1 molar solution? Or moles = Molarity X Liters 4 moles / 2 liters = 2 moles per liter or 2 M 0.5 liters x 1 mole/liter = 0.5 moles

1. What is the concentration of a solution with 0.25 moles of HCl
dissolved in 250 mL of solution? M = moles liters 0.25 moles = 0.250 L 1.0 Molar 2. How many moles of HCl are dissolved in 250 mL of a 0.1 M solution? M = moles liters moles = M x liters 0.1 M = mol 0.250 L mol = 0.1 M x L mol =

3. What mass of NaCl is dissolved in 0.3 liters of a 3 M solution?
Try these on your own: 3. What mass of NaCl is dissolved in 0.3 liters of a 3 M solution? (Find moles of solute first from formula, then convert to mass) 4. What is the molarity of 29 grams of NaCl dissolved in 500 mL of solution? (Find moles of solute first, then calculate molarity)

Try these Regents problems:
Setup

Parts Per Million (PPM)
- grams of solute per 1,000,000 grams of solution - for substances which have very low solubility or very toxic substances ex: oxygen 8 PPM at 250C – 8 milligrams dissolved in 1 liter of water (8 grams per 1,000,000 grams or grams per 1000 g ) PPM = mass of (part) solute X 1,000,000 mass of (whole) solution

PPM = mass of (part) solute X 1,000,000 mass of (whole) solution
1. What is the concentration in PPM of a solution with 0.36 grams of solute dissolved in 2000 grams of solution? PPM = mass of (part) solute X 1,000,000 mass of (whole) solution = x 106 PPM = 0.36g solute___ x 106 2000. g solution = 180 PPM

Try these: setup

Problems 1. A solution has a volume of 2.0 L and contains 36 g of glucose. If the molar mass of glucose is 180 g/mole, what is the molarity of the solution? 2. A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is its molarity? 3. How many moles of ammonium nitrate are in 335 mL of M NN4NO3? 4. How many moles of solute are in 250 mL of 2.0 M CaCl2? How many grams of CaCl2 is this?

Problems 5. If 10 mL of pure acetone is diluted with water to a total solution volume of 200 mL, what is the percent by volume of the acetone in the solution? 6. A bottle of hydrogen peroxide antiseptic is labeled 3.0% (v/v) how many mL H2O2 are in a mL bottle of this solution? 7. Calculate the grams of solute required to make 250 mL of 0.10% MgSO4 (m/v).

Problems 8. A solution contains 2.7 g CuSO4 in 75 mL of solution. What is the percent (m/v) of the solution? 9. What is the concentration, in PPM of a solution with grams of solute dissolved in grams of solution? 10. How many grams of O2 are dissolved in 1500 grams of a solution with a concentration of 10 PPM?

Colligative Properties
Section 3B Colligative Properties

(Adding solutes to water changes water’s properties) Why is antifreeze coolant added to water in a car’s radiator? It keeps the water from boiling in the summer… …and freezing in the winter.

(Adding solutes to water changes water’s properties) Depend ONLY on the concentration of dissolved particles: (not on the identity) Adding solute raises the Boiling point but lowers the Freezing point

Salting roads lowers water’s freezing point causing ice to melt
(Water’s freezing point decreases until it starts to melt)

Why does pasta cook faster in boiling salt water?
(The boiling point increased to the water is now hotter than normal) …it the heat that cooks the pasta.

Solute takes up space in the solution making it more difficult for water to escape as vapor.
Vapor pressure decreases. Water has to get even hotter to get back up to atmospheric pressure!

Also: Ionic (Electrolytes) have greater effect than molecular (non-electrolytes) ex: 1 mole of sucrose dissolves  1 mole molecules 1 mole of NaCl dissolves  1 mole Na + 1 mole Cl = 2 moles total ions

Which salt is more effective?
3 moles of ions Vs moles of ions 1 CaCl2  1Ca2+ + 2Cl- 1 NaCl  1Na+ + 1Cl-

Which has a higher boiling point. Circle one: a
Which has a higher boiling point? Circle one: a. 10 g NaCl in 1000 grams of water or 20 g in 1000 grams of water? b. 1 mole of NaCl or 1 mole of C12H22O11? c. 10 grams of NaCl in 1000 g water or 10 grams in 500 grams of water?

Try these: HDYK

Problems 1. Why does a solution have a lower vapor pressure that the pure solvent of that solution? 2. Would a dilute or a concentrated sodium fluoride solution have a higher boiling point? Explain. 3. An equal number of moles of KI and MgF2 are dissolved in equal volumes of water. Which solution has the higher…Explain a. boiling point b. freezing point 4. List the moles of each ion present in 1 mole of each compound dissolved in water? a. K2SO4 b. Fe(NO3)2

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