1 5-6Electronegativity 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

2 Coordinator: Prof. Arab Qaseer

Ge < As < Se < Br Example 5-11: Arrange these elements based on their electronegativity. Se, Ge, Br, As 3 5-6Electronegativity Example 5-12: Arrange these elements based on their electronegativity. Be, Mg, Ca, Ba Ba < Ca < Mg < Be General Chem. Chap. 5Coordinator: Prof. Arab Qaseer

Chemistry for Health Sciences 4 4 CHEM 122-General Chemistry Lecture 1 General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

6. Some Types of Chemical Reactions General Chem. Chap. 6Coordinator: Prof. Arab Qaseer5 Chapter Goals 1. Aqueous Solutions: An Introduction

6 6-1Aqueous 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: C 2 H 5 OH – ethanol C 6 H 12 O 6 - glucose (blood sugar) C 12 H 22 O 11 - sucrose (table sugar) General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

6-1Aqueous Solutions: An Introduction 7 glucosesucrose The reason nonelectrolytes do not conduct electricity is because they do not form ions in solution. ions conduct electricity in solution General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

8 6-1Aqueous Solutions: An Introduction Strong electrolytes:- conduct electricity extremely well in dilute aqueous solutions Examples of strong electrolytes 1.HCl, HNO 3, 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. 6Coordinator: Prof. Arab Qaseer

9 6-1Aqueous Solutions: An Introduction Weak electrolytes :- conduct electricity poorly in dilute aqueous solutions 1.CH 3 COOH, (COOH) 2 weak acids 2.NH 3, Fe(OH) 3 weak bases General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

10 6-1Aqueous Solutions: An Introduction 2.Strong and Weak Acids Acids are substances that generate H + in aqueous solutions. Strong acids ionize 100% in water. General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

6-1Aqueous Solutions: An Introduction 11General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

12 6-1Aqueous Solutions: An Introduction Weak acids ionize significantly less than 100% in water. –Typically ionize 10% or less! –Example:- CH 3 COOH, acetic acid General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

13 6-1Aqueous Solutions: An Introduction 3.Reversible Reactions CH 3 COOH acetic acid All weak inorganic acids ionize reversibly or in equilibrium reactions. This is why they ionize less than 100%. Correct chemical symbolism for equilibrium reactions General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

14 6-1Aqueous Solutions: An Introducti on 4.Strong Bases, Insoluble Bases, and Weak Bases Bases are substances that generate OH - in aqueous solutions. General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

15 6-1Aqueous Solutions: An Introduction Strong bases ionize 100% in water. Insoluble bases Ionic compounds that are insoluble in water, consequently, not very basic. Examples Fe(OH) 2 iron (II) hydroxide Fe(OH) 3 iron (III) hydroxide General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

16 6-1Aqueous Solutions: An Introduction Weak bases are covalent compounds that ionize slightly in water. Ammonia is most common weak base – NH 3 General Chem. Chap. 6Coordinator: Prof. Arab Qaseer

17 6-9Metathesis Reactions Metathesis reactionsMetathesis 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. 6Coordinator: Prof. Arab Qaseer

18 6-8Metathesis Reactions 1.Acid-Base (neutralization) Reactions 2.Precipitation reactions in which a solid product is formed. Solid product General Chem. Chap. 6Coordinator: Prof. Arab Qaseer