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Solutions and Solubility

Solution: a _______________ mixture (atoms, ions or

molecules) of one substance spread ___________ throughout

a second substance.

A solution can be in solid, gas or liquid phase

•  Solid: metal __________ are solid solutions (example: _______ is a mixture of Cu and Zn, _____________________: Cu and Ag)

• Gas: (air) solution in the gas phase (mixture of different gases O2, N2, CO2, etc.)

•  Liquid: –  Liquid in liquid: two or more liquids mixed

together • _______________ (a pair of liquids that will

dissolve in each other) or _____________ (a pair of liquids that will not dissolve in each other)

–  Solid in liquid: sugar water. C6H12O6 (aq) – Gas in liquid: __________

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How do you know if it's a solution?

• Five properties of a solution…….. • 1. Homogeneous mixtures in which

particles are distributed ___________ throughout. (ex. KCl(aq) )

• 2. Dissolved particles do not _________ on standing.

• 3. Solutions are _________, (even if colored), and do not disperse light. A beam of light will pass through a solution.

____________________________

• 4. Solutions can pass through a ______ unchanged.

• 5. Solutions are considered to be a _____________________(even though components may have been in different phases before the solution was formed).

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• Solute: substance that is ______________ in the liquid. [(s),(g),(l)]

• Solvent: substance in which the solute __________. The symbol (aq) means that the solvent is ________. (alcohol, acetone or turpentine are other examples of solvents)

KBr(aq) KBr is __________ Water is the ____________

SOLUBILITY is..

•  the amount of __________ that can dissolve in a given amount of _________ at a given range of _____________. (see table G in reference charts)

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Table G (SOLUBILITY CURVE) shows how much of a particular solute can dissolve in 100g of water at a specific temperature

Entire table is set up for 100g of water! (100g H2O = 100mL) if you are dissolving something in 200g of water you would have to ___________ the amounts from this chart!

Lines on the graph represent a _________ solution : the maximum amount of solute that can be dissolved at a given temperature.

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-What is the general trend for the solubility of solid solutes as temperature increases?

-What is the general trend for a gas solute as temperature increases?

-how many grams of potassium nitrate will just saturate 100 grams of water at 70 degrees celsius?

-how many grams will saturate 50grams of water at the same temperature?

____________ solution: (masses of solute below the saturated line on solubility curve.) When less than the maximum amount of solute is dissolved at a given temperature. Which solute is this point on the graph unsaturated for???

______________ solution: an unstable solution that contains more dissolved solute than a saturated solution.(masses of solute are above the saturated line on the solubility curve)

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Saturated Solution: Rate of ___________ is equal to the rate of _________________. (dynamic equilibrium)

Unsaturated solution: rate of dissolving is ____________________the rate of crystallization.

Supersaturated solution: rate of crystallization is __________________the rate of dissolving.

Question: What will happen to a saturated solution when the temperature drops?

Answer:

If solute is added to an unsaturated aqueous solution …what will happen to the solute?

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Solubility ratios Question: How many grams of NaNO3 would be needed to saturate 200g of H2O at 40ºC? Look up solubility for 100g H2O on table G, then set up a ratio for 200g of water.

At 40 C sodium nitrate is saturated with 105g. This is for 100g of water!

NEVER include temperature in the ratio!!!! Only mass of solute per mL of water.

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PRACTICE QUESTIONS

1. If 60 g of KNO3 is dissolved in 100 mL of water at 50 degrees C, the solution will be…

a) saturated b) unsaturated c) supersaturated d) dilute

2.  At what temperature will 50 grams of NH4Cl just saturate 100 grams of water?

a) 28C b) 33C c) 45C d) 56C

3.  As additional KNO3 (s) is added to a saturated solution of KNO3 at constant temp., the concentration of the solution

a) decreases b) increases c) remains the same

3 ways to increase the rate of dissolving of a solid solute…

-increase __________________

-increase _____________ of solute. (crushing to decrease particle size)

-______________

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Factors that affect solubility…

1. Temperature:

*solids become more soluble with _______________ temperature. *gases become ___________ soluble with increasing temperature.

2. Pressure:

*Changes in ___________ affect solubility of gases- not liquids or solids*

As pressure ____________, the solubility of gas in liquid increases.

3. Type of solute/solvent: "like ____________ like"

-Polar/ ionic substances dissolve, are miscible, in ___________ solvents

-Nonpolar substances dissolve, are miscible, in ____________ solvents

NaCl(s) dissolves in H2O. Polar solvents, such as H2O have a (+) and (-) end.

i.e. salts (ionic) dissolve in water (polar)

Fat/oil/grease (nonpolar) will dissolve in _______________(nonpolar)

QUESTION: Will CH4 (l) dissolve in H2O?

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Solubility Guidelines…

Reference Table F: Determining if compounds are soluble or insoluble in aqueous (water) solutions.

*Soluble compounds _________________in water.

*Insoluble compounds dissolve ______________________. Insoluble means it has a low concentration of dissolved ions.

*LEFT BOX lists ions that are SOLUBLE in compounds.

Exceptions on the left form INSOLUBLE compounds

* RIGHT BOX lists ions that form INSOLUBLE compounds

Exceptions on the right form SOLUBLE compounds

LiCl is __________________

PbCl2 is ________________

CaCO3 is ___________________

(NH4 ) 2CO3 is _________________

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HOW DO COMPOUNDS DISSOLVE? (IONIC VS. MOLECULAR)

IONIC: Salt Solution

NaCl(s) Na+(aq) + Cl-(aq) 1mol NaCl 1mol Na+ and 1mol Cl-

(____________________in solution into ions)

One mole of NaCl breaks into ________ moles of ions

How many moles of ions will one mole of Al2S3 form when it dissolves?

Al+3 Al+3 S-2 S-2 S-2

_________ moles of ions!

REMINDER: salts in aqueous solutions are _______________________ (they conduct electricity) due to mobile ions!

Acids and bases __________in aqueous solution and therefore conduct ___________because of mobile ions

Acids and bases are also electrolytes!

See reference tables for list of common acids (table K) and bases (table L)

Dissociation (ionization) of an acid…..

HCl(aq) à H+ + Cl-

HNO3 (aq) à H+ + NO3-

Dissociation (ionization) of a base…..

NaOH (aq) à Na+ + OH-

KOH(aq)à K+ + OH-

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As a salt dissolves it becomes more __________

ENTROPY… is a measure of the disorder in a system

The greater the disorder the greater the ________

NaCl (s) low entropy NaCl(aq) high entropy

When MOLECULAR substances dissolve…

- The ATOMS ARE COVALENTLY BONDED

- MOLECULES STAY ___________ IN SOLUTION

- Bonds don’t break when substance dissolves (a ______________)

Sugar Solution C12H22O11 (s) --- C12H22O11(aq)

1mol 1mol

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Review Questions 1. Which of the following compounds is least soluble in water?

a) NaCl b) Pb2ClO3 c) Na2CrO4 d) PbCrO4

2. Which of the following saturated solutions contains the least concentration of dissolved ions?

a) NaCl(aq) b) MgCl2(aq) c) NiCl2(aq) d) AgCl (aq)

3. Which of the following is not soluble? a) sodium chromate b) lead(II) iodide

c) lithium hydroxide d) ammonium sulfate

Write the balanced equations

• solution of strontium chloride is mixed with solution of potassium sulfate – SrCl2(aq) + K2SO4(aq) à SrSO4(s) + 2KCl(aq)

• solution of sodium sulfide and solution of iron (II) nitrate are mixed – Na2S(aq) + Fe(NO3)2(aq) à 2NaNO3(aq) + FeS(s)

• Solution of aluminum chloride and solution of silver nitrate are mixed – AlCl3(aq) + 3AgNO3(aq) à 3AgCl(s) + Al(NO3)3(aq)

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Types of Reactions

•  ___________________ – overall reaction – normal type we have been writing

•  ___________________ – all strong electrolytes are broken into ions

•  ___________________ – all spectator ions are cancelled out – only includes species active in chemical

reaction

Types of Electrolytes

•  Break Apart (Strong) – must be (aq) – soluble ionic

compounds – strong acids: HCl,

HBr, HI, HNO3, HClO4, H2SO4

•  Don’t break apart (weak/non) – anything (g), (s), (l) – weak acids

(compounds with H in front other than those listed to left)

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Tips for writing equations

•  balance at the beginning – should stay balanced the whole way through – may simplify at the end if necessary

•  all ions should be ______ •  keep symbols written through entire

process

Write the net ionic equations

• solution of strontium chloride is mixed with solution of potassium sulfate

• complete ionic:

• Spectators: • net ionic:

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Write the net ionic equations

•  solution of sodium sulfide and solution of iron (II) nitrate are mixed

•  complete ionic:

•  Spectators: •  net ionic:

Colligative Properties Properties of a solution that depend on the ___________ (concentration) of ______________ (dissolved particles).

RULE 1: Boiling point elevation

-the presence of solute (dissolved particles) _________ the boiling point of the solvent. The ___________ the concentration of solute the more it would raise the boiling point.

-the greater the number of dissolved particles the __________ the boiling point elevation

2M KCl raises the boiling point of a solution ______________1M KCl

1M Al2S3(aq) will elevate boiling point more than 1M KCl(aq) because Al2S3 produces more dissolved particles (five moles of ions) than 1M KCl (two moles of ions)

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RULE 2: Freezing point depression The presence of any solute _____________ the freezing point of the solvent. The greater the concentration of solute the _____________ the amount of freezing point depression (lowering).

RULE 3: Decrease in Vapor pressure

dissolved particles prevent molecules from ______________, thus _________________ vapor pressure. (increase in solute concentration, decrease in vapor pressure)

CONCENTRATION

The number of particles in a given volume.

• # of particles = moles

• Volume = Liters (L)

• Units for Concentration = Molarity (M)

Molarity = moles/Liters M = mol/L

Example… What is the concentration of a 2 L salt solution that contains

5.5 moles of NaCl?

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MOLARITY (M) tells you the ______________ of a solution.

A 4M solution is more ______________ than a 2M solution because it has more dissolved particles per unit volume.

Other ways of expressing solution concentration are…. -Parts per million (ppm) -percent by volume -percent by mass

1. Parts per million (ppm)

is used for solutes with very ________ concentrations.

ppm= grams solute x 1,000,000 grams solution

example: A solution contains .05g CuSO4 solute in 1000g of solution. Express the concentration in ppm.

Be sure to add in the mass of the solute in your set-up!

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2. Percent by volume= mL solute x 100 mL solution

example: What is the percent by volume of alcohol if 50mL of ethanol is diluted with water to form a total volume of 300mL?

3. Percent by mass = mass of part x 100 mass of whole

Dilution Calculations

M1V1 = M2V2

compare initial (the ones) and final (the twos) molarity and volume in calculations

M= molarity V= volume

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Example… 5 L of a 6M solution has been diluted to 2 M.

What is the new volume of this solution?

M1V1 = M2V2

1.  A 2L solution of NaOH (aq) is diluted from 10M to 4M. What is the volume of the diluted solution?

2. Stock solution of HCl (aq) has a volume of 1L and a concentration of 18M. If the solution was diluted to a volume of 6L, what is the diluted concentration?

3.How much water must be added to 2L of a 3M solution in order to make the diluted concentration 0.5M?

Try these…..