1

5-6 Electronegativity

• Electronegativity is a measure of the relative tendency of an atom to attract electrons to itself when chemically combined with another element.– Fluorine is the most electronegative element.– Cesium and francium are the least electronegative elements.

• For the representative elements (G1A-G8A), electronegativities usually increase from left to right across periods and decrease from top to bottom within groups.

General Chem. Chap. 5

2General Chem. Chap. 5 Coordinator: Prof. Arab Qaseer

Ge < As < Se < Br

Example 5-11: Arrange these elements based on their electronegativity.

Se, Ge, Br, As

3

5-6 Electronegativity

Example 5-12: Arrange these elements based on their electronegativity.

Be, Mg, Ca, Ba

Ba < Ca < Mg < BeGeneral Chem. Chap. 5 Coordinator: Prof. Arab Qaseer

Chemistry for Health Sciences

44

CHEM 122-General Chemistry

Lecture 1

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

6. Some Types of Chemical Reactions

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer 5

Chapter Goals

1. Aqueous Solutions: An Introduction

6

6-1 Aqueous Solutions: An Introduction

1. Electrolytes and Extent of Ionization• Aqueous solutions consist of a solute dissolved in water.

Classification of solutes:Nonelectrolytes:-solutes that do not conduct electricity in water

Examples: C2H5OH – ethanol

C6H12O6 - glucose (blood sugar)

C12H22O11 - sucrose (table sugar)

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

6-1 Aqueous Solutions: An Introduction

7

glucose sucrose

The reason nonelectrolytes do not conduct electricity is because they do not form ions in solution.

ions conduct electricity in solution

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

C

OC

C

C C

C

H

H

OH

H OH

OH

H

OH

OH H

H

H

C

OC

C

C C

CH2

H

H

OH

H

OH

OH

HO

H

OH

C C

C

O

C

CH2

H

OH

H

H

OH

CH2

OH

OH

8

6-1 Aqueous Solutions: An Introduction

Strong electrolytes:- conduct electricity extremely well in dilute aqueous solutions• Examples of strong electrolytes

1. HCl, HNO3, etc.• strong soluble acids

2. NaOH, KOH, etc.• strong soluble bases

3. NaCl, KBr, etc.• soluble ionic salts• ionize in water essentially 100%

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

9

6-1 Aqueous Solutions: An Introduction

Weak electrolytes :-

conduct electricity poorly in dilute aqueous solutions

1. CH3COOH, (COOH)2 • weak acids

2. NH3, Fe(OH)3 • weak bases

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

10

6-1 Aqueous Solutions: An Introduction

2. Strong and Weak Acids• Acids are substances that generate H+ in

aqueous solutions.• Strong acids ionize 100% in water.

-aqaq

%100g Cl H HCl

-

aq3aqOH

3

-aq3aq3

100%2 3

NO + H HNO

or

NO + OH OH HNO

2

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

6-1 Aqueous Solutions: An Introduction

11General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

12

6-1 Aqueous Solutions: An Introduction

• Weak acids ionize significantly less than 100% in water.– Typically ionize 10% or less!– Example:- CH3COOH, acetic acid

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

13

6-1 Aqueous Solutions: An Introduction

3. Reversible Reactions• CH3COOH acetic acid

All weak inorganic acids ionize reversibly or in equilibrium reactions.This is why they ionize less than 100%.

aq-aq3

7%

3 H + COOCH COOHCH

Correct chemical symbolism for equilibrium reactions

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

14

6-1 Aqueous Solutions: An Introduction

4. Strong Bases, Insoluble Bases, and Weak Bases

Bases are substances that generate OH- in aqueous solutions.

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

15

6-1 Aqueous Solutions: An Introduction

Strong bases ionize 100% in water.

(aq)OH 2 + (aq)Ba Ba(OH)

(aq)OH + (aq)K KOH-+2

2

-+

Insoluble bases Ionic compounds that are insoluble in water,

consequently, not very basic.ExamplesFe(OH)2 iron (II) hydroxideFe(OH)3 iron (III) hydroxideGeneral Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

16

6-1 Aqueous Solutions: An Introduction

Weak bases are covalent compounds that ionize slightly in water.

Ammonia is most common weak base– NH3

-(aq)aq42g3 OH + NH OH + NH

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

17

6-9 Metathesis Reactions

• Metathesis reactions occur when two ionic aqueous solutions are mixed and the ions switch partners.

AX + BY AY + BX• Metathesis reactions classified into two types:

1. Acid – Base neutralization 2. Precipitation Reactions

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer

18

6-8 Metathesis Reactions

1. Acid-Base (neutralization) Reactions

)(2 (aq)(aq)(aq) OH + KBr KOH + HBr

)(2aq)(23(aq)3(aq)2 OH 2 + )Ca(NOHNO 2 + Ca(OH)

2. Precipitation reactions in which a solid product is formed.

4(s))aq(aq)(42(aq)2 BaSO +NaCl 2 SONa + BaCl Solid product

General Chem. Chap. 6 Coordinator: Prof. Arab Qaseer