General Chemistry

General Chemistry

Faculty of Allied Medical Sciences

(MGGC-101)

Supervision:Prof.Dr.Shehata El-Sewedy

Dr.Fatma Ahmed

Chemical bonds &chemical reactions

Outcomes By the end of this lecture, the

students will be able to1-Understand the meaning of chemical bond

2-learn to type of chemical bond3-To differentiate between solute, solvent and

solution4-Recognize the meaning of electrolyte

5-To know types of chemical reactions6-To differentiate between acids and bases

Chemical bonds

CHEMICAL BONDS: THE OCTET RULE Why do atoms bond together? More stable (has less energy)  Octet Rule

Atoms form bonds to produce the electron configuration of a noble gas

because the electronic configuration of noble gases is particularly ) stable)

For most atoms of interest this means achieving a valence shell

configuraon of 8 electrons corresponding to that of the nearest noble gas

Atoms close to helium achieve a valence shell configuraon of 2 electrons

Atoms can form either ionic or covalent bonds to satisfy the octet rule

 How to describe bonding?

The ionic bond: formed by the transfer of one or more

electrons from one atom to another to create ions  The covalent bond: results when atoms share

electrons Atoms without the electronic configuration of a noble gas

generally react to produce such a configuration

1 )Ionic Bonds

Results from transfer of electrons from one atom to another such as NaCl, NaBr and so on.

Na Na + e

Cl + e Cl

Na + Cl NaCl

ionic bond

Electronegativitymeasures the ability of an atom to attract electrons

Ionic Bonds: One Big Greedy Thief Dog!

Electronegativities of Some of Elements

  The electronegativity increases across a

horizontal row of the periodic table from left to right

The electronegativity decreases go down a vertical column

F>O>N>C

fluorine is the most electronegative atom.  Ionic substances, because of their strong internal electrostatic forces, are usually very high melting solids, often having melting points above 1000 °C

H + H H-Hcovalent bond

H + Cl H-ClPolar covalent bond

2) Covalent Bonds Results from sharing of electrons by two atoms such as H-H, Cl-Cl, H-Cl and so on.

Polar covalent bond ( between two atoms different in electronegativity)

Polar Covalent Bonds: Unevenly matched, but willing to share.

Chemical reactions

Chemical reaction

Reaction without electron transfer Reaction with electron transfer

2H2 + O2 2H2O Sn 2 Sn 4+ 2e

1-Combination 1-Oxidation (loss of electrons)

Cl + CH3Br CH3Cl + Br Fe3

+ e Fe2

2-Substitution 2-Reduction (gain of electrons)

BF3 + NH3 BF3 NH3 MnO4 + 5 e + 8H Mn + 4H2O2

3-Addition 3-Redox reaction(oxidation-reduction)

4-Combustion

CH4 + 2O2 CO2 + H2O

A solution is a homogenous mixture of 2 or more substances

The solute is)are) the substance)s) present in the smaller amount)s)

The solvent is the substance present in the larger amount

Solution Solvent Solute

Soft drink )l) H2O Sugar

An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity.A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.

nonelectrolyte weak electrolyte strong electrolyte

Acid–base reactions

Acids : Is the substance that produces H+ ions when it dissolved in Waterstrong acid; it is a strong electrolyte.weak acid:it is a weak electrolyte.

Acids can be divided into two classes

Strong Acids : Completely dissociate into its ions eg: HCl, HBr, HNO3 and H2SO4

HCl (aq) → H+ (qa) + Cl- (aq) 100% dissociation

Weak acids : is the one dissociate incompletely into its ions eg: CH3COOH.

CH3COOH ↔ H + (aq) + CH3COO- (aq) 1% dissociation

Base : Is the substance that produces OH- ions when it dissolved in water

strong base; it is a strong electrolyte.weak base:it is a weak electrolyte.

Bases: can be divided into two classes Strong Bases : Completely dissociate into its ions eg: NaOH and KOHNaOH (aq) → Na+ (qa) +OH- (aq)

100% dissociation Weak Base : is the one dissociate incompletely into its ions eg: ammonia.

NH3(aq) + H2O(l) ↔ NH4 + (aq) + OH- (aq)

1% dissociation

Examples of the acid-base reactions: Reaction of Sodium hydroxide and Nitric acid & reaction of Potassium hydroxide and Sulfuric acid. 

The Brønsted - Lowry theory of acids and bases.A Brønsted – Lowry acid: is a species which donates a proton (H+ ion) to another species.A Brønsted – Lowry base: is a species which accepts a proton from another species. You must have a reaction in order to name a species as a Brønsted - Lowry acid (B-L acid) or base.

Example HCl(aq) + H2O (l) H3O+

(aq) + Cl-(aq)

HCl is the B-L acid, it donates the proton to the H2O which is the B-L base since it accepts the proton (H+ion)

Example NH3(g) + H2O(l) NH4

+(aq) + OH-

(aq)H2O is the B-L acid, it donates the proton to the NH3 which is the B-L base since it accepts the proton (H+ion).

Quiz time

Mention Brønsted - Lowry theory of acids and bases for the fowlloing reaction

NH3(g) + H2O (l) NH4+

(aq) + OH-(aq)

HCl(aq) + H2O (l) H3O+(aq) + Cl-

(aq)

NH3(aq) + H2O(l) ↔ NH4 + (aq) + OH- (aq)

What is type of base for NH3 ?

HCl (aq) → H+ (qa) + Cl- (aq)

What is type of acid for HCl ?

N,C, F,O ,

Order according for electronegativity ?

Fe3

+ e Fe2

Cl + CH3Br CH3Cl + Br

BF3 + NH3 BF3 NH3

CH4 + 2O2 CO2 + H2O

Mention types of reaction ?

Student Question

Fe3

+ e Fe2

Cl + CH3Br CH3Cl + Br

BF3 + NH3 BF3 NH3

CH4 + 2O2 CO2 + H2O

Mention types of reaction ?BaseAcidssoluteelectrolyte

Define and give example

Mention Brønsted - Lowry theory of acids and bases for the fowlloing reaction

NH3(g) + H2O(l) NH4+

(aq) + OH-(aq)

HCl(aq) + H2O (l) H3O+(aq) + Cl-

(aq)

NH3(aq) + H2O(l) ↔ NH4 + (aq) + OH- (aq)

What is type of base for NH3 ?

HCl (aq) → H+ (qa) + Cl- (aq)

What is type of acid for HCl ?

N,C, F,O ,

Order according for electronegativity ?

AssignmentsGroup A and Group B

Noor El-Din AdelMohamad Abd El FatahAli Mahmoud Ahmad

Combustion reaction

Naamat Hafez Mana Allah MostafaPassant Ahmad Hamza

Substitution reaction in industry

Ashraf MoahamadEl Amir Said TawfikIbrahim ShahaatAhmad Mahmoud Raafat AbdAllah

Application of redox reaction

Abeer El Said -Haidy Adel- Ali HassanHossam Hassan- Yehia HamdyYoussef Ali

Physical properties of matter

RECOMMENDED TEXTBOOKS:

1-Raymond Chang. Chemistry. 10th ed. 20092-Zumdehl. International edition. 2009