UNIT IXSolution Chemistry

Lesson #1

INTRODUCTION

Solution Chemistry is the study of chemical reactions that occur in solutions…

Reactions in solutions are chemists’ favourite type of reactions…because of how easy and convenient they are.

Compare to:Reactions in the gas phase are complicated need special containers (air-tight)Solid reactions very slow or do not occur at all

INTRODUCTION

In this unit, we will deal with liquid or solid solutes that are dissolved in liquid solvents…

(not pure solids, liquids or gases)

LET’S REMEMBER SOME DEFINITIONS

Solution:

 Solvent:

 Solute:

SOLUTIONS AND SOLUBILITY

Saturated solution:

 

Unsaturated solution:

Solubility:

Saturated Vs Unsaturated

SOLUTIONS AND CONDUCTIVITY

Do all solutions conduct electricity?

How do we know?

Requirements to conduct electricity

Experiments tell us that you need…

Electrical charge to be transferred in the solution in order to produce electricity.

IONS carry electrical charge!

Requirements to conduct electricity

IONS carry electrical charge!

Therefore, Ionic compounds can conduct electricity

NaCl(aq)

Can covalent compounds conduct electricity?

CS2(aq)

THE CONDUCTIVITY OF AQUEOUS SOLUTIONS

A conducting solution contains ions; the greater the concentration of ions, _____________the conductivity.

A compound made up of a METAL and NONMETAL is IONIC, and forms a conducting solution in water because it breaks into ________

A substance made up of a NONMETAL and a NONMETAL is COVALENT, and will NOT form a conducting solution in water because it stays as a molecular compound.

NaCl (Ionic) in water

The "+" and "-" ions are now free to move around. The "+" ions would be attracted to a negative electrode and the "-" ions would be attracted to a positive electrode. In this way, the ionic solution conducts a current. 

What else can conduct electricity??

ACIDS and BASES form conducting solutions in water.

Why? Because they can break into ions! HCl

NaOH

What else can conduct electricity??

ACIDS and BASES form conducting solutions in water.

1- Think of acids as any compounds that starts with H

2- Think of bases as any compounds that end with OH

Exception; if a compound starts with Carbon and ends with OH. It is an alcohol, not a base and can’t conduct electricity.

Ex: CH3OH (can’t conduct electricity)

What else can conduct electricity??

Metals (only in liquid or aqueous phases) can conduct electricity

Examples: Na(l), Cu(aq), Ag(aq)

Ex: Na(s) can’t (because it is a solid!!!) Na(l) or Na(aq) can

So what can’t conduct electricity??

1) Non-metals

2) Covalent compounds

3) Organic compounds(usually start with Carbon-C- and contain hydrogens)Ex: CH3OH, C14H10

*CH3COOH (exception)

4) Solids

TO CONDUCT or NOT TO CONDUCT??? This is the question.....

CONDUCT DOESN’T CONDUCTMetals non metalsionic solidacids covalentbases * organic

compounds*CH3COOH (exception)

 http://www.youtube.com/watch?v=UHYWIM8AbPE

THINK ABOUT THIS

For solutions to form, and to mix chemical compounds together when adding a solute to a solvent to make a solution…bonds need to break and new bonds need to form!

So, we need to remember the intermolecular forces that hold molecules together….

Back to forces between molecules…

Van der Waals Forces:

THREE main types:

A.DIPOLE-DIPOLE FORCES

B.LONDON FORCES

C.HYDROGEN BONDING

All are caused by dipoles!

A. A. DIPOLE-DIPOLE FORCES

Caused by dipoles

Dipole: A temporary separation of charges, where more electrons are found on one side on the atom than the other side.

  Dipole-Dipole Forces: a permanent dipole

results from atoms with different ELECTRONEGATIVITY!

DIPOLE-DIPOLE FORCES

Ex:

HCl H2O

London Forces:

LONDON FORCES exist for everything!!!

London forces’ strength increases as the # of electrons is increased.

Ex: Does He or Xe have a stronger london forces bond?

B. LONDON FORCES

C. HYDROGEN BONDING  Hydrogen Bond: strong dipole – dipole attraction

between molecules containing a H – N, H – O, or H – F bond

(because N,F and O are highly electronegative)

 *intermolecular bond (between molecules)

*strongest van der Waals bonds – but still weaker than covalent and ionic

 

C. HYDROGEN BONDING  Hydrogen Bond: strong dipole – dipole attraction

between molecules containing a H – N, H – O, or H – F

Ex: NH3 and NH3  H2O and H2O

Hint: Look for HF or any molecule having OH or NH in its formula

COMPARING STRENGTHS OF BONDS

IONIC BOND DIPOLE – DIPOLE ~ LONDON FORCE

Intramolecular Intermolecular Ionic bonds will always be stronger than any intermolecular bond.Remember, London forces strength increases with the increased number of electrons.

EXPLAIN THIS:

Boiling temperatures:

ICl = 97 C (70 electrons)Br2 = 59 C (70 electrons)

HOMEWORK

Page 198,199Questions 6,7 Question 8 (do a,c,e, etc)Question 9

Page 202, 203, 204Question 11 and Question 12Question 14 and Question 16