Chemistry 12

Name: ___________________________

Solutions & their Concentrations Definitions Solution:

a homogeneous mixture composed of a solute and a _______________

Solute:

the substance being dissolved

Solvent:

the substance that has other substances dissolved in it

NOTE: solutes and solvents can be either gases, liquids or solids Examples: 1.

Air

- a solution of gases (_______________, oxygen, carbon dioxide, etc.)

2.

Vinegar

- a solution of liquids (5% acetic acid + 95% water)

3.

Metal alloy

- a solution of solids (eg. sterling silver is a mixture of silver & copper)

4.

NaCl(aq)

- a solid ionic compound dissolved in a liquid (water)

5.

NH3(aq)

- a gaseous molecular compound dissolved in a liquid (water)

A.

IMPORTANCE OF SOLUTIONS

Solutions are important to non-living systems:  Eg: in order for chemical reactions to occur, _______________ must often be dissolved in water Solutions are important to living systems  Eg. Blood plasma is mostly water with substances such as O2 and CO2 dissolved in it B.

CLASSIFYING SOLUTIONS

1.

Electrolytes and Non-electrolytes:

a)

Electrolytes: conduct electricity  an electric current involves the _______________ of _______________ particles, therefore solutions containing ions will conduct electricity  include acids, bases and neutral ionic compounds in solution

b)

Non-electrolytes: do not conduct electricity  include neutral molecular compounds in solution

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Chemistry 12

Name: ___________________________

2.

Concentrated and Diluted Solutions:

a) b)

Concentrated solution: has a relatively ___________ quantity of solute in a given volume Diluted solution: has a relatively small quantity of solute in a given volume

3.

Acids, Bases and Neutral Solutions:

a) b) c)

Acids: substances that produce H+ ions in solution Bases: substances that produce OH- ions in solution Neutral: substances that do not produce H+ or OH- ions in solution

4.

Saturated, Supersaturated and Unsaturated Solutions: 

depends on the _______________ of the solute in a particular solvent:

Solubility:  the maximum amount of a solute that dissolves in a given quantity of solvent at a certain temperature  eg. the solubility of NaCl in water at 200C is 36 g per 100 mL 

The ability of a solvent to dissolve a solute depends on the attractive forces between the particles  All ionic substances dissolve in water to varying degrees: Insoluble: (<0.01 mol/L) Soluble:

High Solubility ( ≥0.1 mol/L) Low Solubility (<0.1 mol/L but > 0.01 mol/L)

a)

Saturated solution  A solution that contains the _____________ amount of solute at a given temperature  A saturated solution is formed when no more solute will dissolve in a solution and excess solute is present  eg. 100 mL of a saturated solution of NaCl in H2O at 200C contains 36g of NaCl. The solution is saturated only with respect to NaCl.

Dynamic Equilibrium:  the balance that exists when 2 opposing _______________ occur at the same time  In a saturated solution, although no changes appear to occur, dissolving and recrystallizing continues. These 2 processes continue at the same rate (speed), therefore no net change in concentration occurs and the solution is in “dynamic equilibrium”. The rate of dissolving = the rate of recrystallization b)

Supersaturated solution  Forms when a saturated solution is heated so that the _______________ solute present dissolves. If the solution cools slowly the excess solute does not immediately crystallize.  A supersaturated solution holds a greater amount of solute than the equilibrium amount. It is in an unstable state that persists as long as it is undisturbed.

c) Unsaturated solution  A solution containing less than the _______________ amount of solute 2

Chemistry 12

C.

Name: ___________________________

BEHAVIOR OF SUBSTANCES IN SOLUTION

Arrhenius:

Scientist who hypothesized that particles of a substance, when dissolving, separate from each other. This idea helped to explain the behavior of electrolytes and non-electrolytes in solution

Dispersion:

occurs when _______________ separate from each other when they dissolve in water (or other solvents); they do not separate into individual atoms or ions, therefore they do not conduct electricity Eg. Figure 1:

C6H12O6(s)



C6H12O6(aq)

Dissociation: occurs when ____________ compounds separate into individual aqueous ions when they dissolve in water, therefore they conduct electricity Eg. Figure 2: NOTE:

NaCl(s)

 Na+(aq)

+

Cl-(aq)

Ionic compounds vary in their ability to conduct electricity, depending on their solubility in water (determined from solubility table)

High Solubility:

All of the formula units dissociate in water = strong electrolytes

Low Solubility:

Only some of the formula units dissociate; most remain intact in water = weak electrolytes Eg. CaCO3(s)  CaCO3(s)

Figure 1

Figure 2

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Chemistry 12

Ionization:

Name: ___________________________

occurs when _______________ separate into individual molecules when dissolved in water and then ionize into positive hydrogen ions and negative ions, therefore they conduct electricity Eg.

NOTE:

HCl(g)  H+(aq)

+

Cl-(aq)

Acidic solutions vary in their ability to conduct electricity, depending on their degree of ionization in water.

Strong Acids: Include HCl, HBr, HI, H2SO4, HNO3, HClO4 These are very good conductors since almost all of the molecules ( 99%) ionize in solution ie. _______________ electrolytes Weak Acids: Include all other acids These are fair to poor conductors since the degree of ionization varies, but for most weak acids it is  50 %, therefore most of the molecules present simply disperse like other molecular compounds ie. _______________ electrolytes Eg:

EXERCISE:

CH3COOH(l)  CH3COOH(aq)

For each of the following chemicals, write equations to represent their dispersion, dissociation, or ionization when they are placed in water.

a)

solid ammonium sulfate

b)

liquid hydrogen nitrate

c)

liquid methanol

d)

solid sodium fluoride

e)

liquid hydrogen sulfite

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Chemistry 12

Name: ___________________________

SUMMARY:

STATE & BEHAVIOR OF SUBSTANCES IN WATER

-- depends on the type of substance and its _______________ in water

Low Solubility:

same state as pure form

Type of Substance

Includes

Ionic

see solubility table

Molecular

Hydrocarbons

High Solubility:

Examples

AgCl(s) CH4(g), C3H8(g), C6H6(l)

Electrolytic Ability

Weak Electrolyte

Non-electrolyte

aqueous ions or molecules

Type of Substance

Includes

Behavior

Examples

Electrolytic Ability

Ionic

See solubility table

Dissociate

NaCl(s) Na+(aq)+Cl-(aq)

Strong Electrolyte

Strong Acid

HCl, HBr, HI, H2SO4, HNO3, HClO4

Ionize

HCl(g)  H+(aq) + Cl-(aq)

Strong Electrolyte

Weak Acid

all other acids

Disperse

HNO2(l)  HNO2(aq)

Weak Electrolyte

Molecular

CH3OH(l), C2H5OH(l) H2O2(l), C12H22O11(s), C6H12O6(s)

Disperse

H2O2(l)  H2O2(aq)

Non-electrolyte

5

Chemistry 12

Name: ___________________________

IONIC EQUATIONS 1.

Nonionic Equations  Elements and compounds are written in their molecular or formula unit forms  Eg: 2 AgNO3(aq) + BaCl2(aq) → 2 AgCl(s) + Ba(NO3)2(aq)

2.

Total Ionic Equations  Elements and compounds are written in the form in which they mainly occur:  Electrolytes are written in ion form  Nonelectrolytes, precipitates and gases are written in their molecular or formula unit forms  Eg: 2Ag+(aq) + 2NO3-(aq) + Ba2+(aq) + 2Cl-(aq) → 2 AgCl(s) + Ba2+(aq) + 2NO3- (aq)

3.

Net Ionic Equations  Only those molecules, formula units or ions that have changed in form are included in the equation = the predominant reacting species  Ions or molecules that do not change, are omitted = spectator species Eg: 2Ag+(aq) + 2Cl-(aq) → 2 AgCl(s) which reduces to: Ag+(aq) + Cl-(aq) → AgCl(s)

Summary of writing net ionic equations:  Species that do not change or take part in the _______________ are not shown.  The equations must be balanced, both in atoms and in charge, using the lowest whole number ratio.  Species are written in the form in which they actually exist. Acids: Acid solutions are written in molecular form except for the 6 strong acids which are written in ionic form: Hydrochloric acid:

HCl(aq) → H+(aq) + Cl-(aq)

Hydrobromic acid:

HBr(aq) → H+(aq) + Br-(aq)

Hydroiodic acid:

HI(aq) → H+(aq) + I-(aq)

Perchloric acid:

HClO4(aq) → H+(aq) + ClO4-(aq)

Nitric acid:

HNO3(aq) → H+(aq) + NO3-(aq)

Sulphuric acid:

H2SO4(aq) → H+(aq) + HSO4-(aq)

NOTE: Only aqueous ionic compounds and strong acids are written as _______________ aqueous ions (in total ionic or net ionic equations). All other species remain intact.

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Chemistry 12

Name: ___________________________

Examples: 1.

Zinc reacts with hydrochloric acid.

Nonionic: Total ionic: Net ionic:

2.

Magnesium reacts with acetic acid.

Nonionic: Total ionic: Net ionic:

3.

Sodium reacts with water.

Nonionic: Total ionic: Net ionic:

4.

Copper reacts with a silver nitrate solution.

Nonionic: Total ionic: Net ionic:

5.

Chlorine reacts with a potassium iodide solution.

Nonionic: Total ionic: Net ionic:

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Chemistry 12

6.

Name: ___________________________

Solutions of barium chloride and potassium sulphate are mixed.

Nonionic: Total ionic: Net ionic:

7.

Nitric acid reacts with aqueous strontium hydroxide.

Nonionic: Total ionic: Net ionic:

8.

Calcium reacts with water.

Nonionic: Total ionic: Net ionic:

8