Acids and Bases

Acids and Bases and Salts

Acids

An acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance. When an acids dissolves in water it donates it's hydrogen ions to the water molecules .

For example

HCl  (g)+ H2O (l)  $\rightarrow$  H30+ (aq)  + Cl- (aq)

Types of Acids

The basicity of an acid is the number of H+ ions produced per mole of acid reacted.

General properties for acids

How do you identify acids?

monobasic acids

produce one mole of H+ ions per mole of acid. For example:
HCl (aq) $\rightarrow$  H+ (aq) + Cl- (aq)

1 mole       1 mole

Dibasic acids

produce two moles of H= ions per mole of acid. for example,
H2SO4 (aq)  $\rightarrow$  2H+ (aq) + SO4  $2-$  (aq)

1mole                  2 moles

Tribasic acids

Produce three moles of H+ ions per mole of acid. For example,
H3Po4(aq)  $\rightarrow$  3H+ (aq) + PO4   3- (aq)

1 mole                3 moles

Acids in real life

list three items/substances in real life which contain acids

The strength of acids

Strong acids and weak acids

Strong acids

dissolves completely in water to produce the maximum number of H+ ions. For example,
HCl (aq)  $\rightarrow$  H+(aq)   + Cl- (aq)

Also, the pH for strong acid is very low.

Weak acids

dissolves partially in water, the contain low concentration of H+ ions. For example,
CH3COOH (aq)  $\rightarrow$  CH3COO- (aq) + H+ (aq)

Also, the pH for weak acids is very high

Question

How can you distinguish strong acids from weak acids using pH?

List 10 items in your home that are acids or base, where on the pH scale would these items fall (five of each).

Bases

definition and properties of bases and their uses in daily life.

What is a base?

A base can be defined as a substance that will react with n acid to from salt and water only. A proton (H+ ion) acceptor.

An Alkali is a base which dissolves in , or react with, water to form a solution which contains OH- ions forming what is called an alkaline solution.

Properties of a base

what are the characteristics of bases and how can we recognize a base?

Strengths of bases

Similarly to acids, a strong base completely dissolves in water, their solutions contain a high concentration of OH- ions. For example,
NaOH(aq)  $\rightarrow$  Na+ (aq) + OH-(aq)

On the other hand, a weak base does not completely dissolves in water, their concentration of OH- ions is very low. For example, 
NH3(g) + H2O(l)  $\rightarrow$  NH4 +(aq)  + OH-(aq)

Oxides

Oxides are chemical compounds with one or more oxygen atoms combined with another element (e.g. Li2O). CO2, SO2, CaO, CO, ZnO, BaO2, H2O, etc. Based on their acid-base characteristics oxides are classified as acidic, basic.

Acidic oxides

An oxide that combines with water to give an acid is termed as an acidic oxide. Acidic oxides are the oxides of non-metals (Groups 14-17) and these acid anhydrides form acids with water. For example,

SO2+H2O→H2SO3 (Sulfurous acid)

Basic oxides

The oxide that gives a base in water is known as a basic oxide. (when an oxide reacts with water to produce a base. Group 1 and 2 elements form basic oxides. For example,
K2O (s) + H2O (l)  $\rightarrow$  2KOH (aq)

Recap

• Explain what an acid, base an d alkalis are?

• What are the properties of acids and base, and how do we recognize them.

• List three items in real life that are acids or bases

• Differentiate between acids and bases base on their strengths.

Salts

A slat is a compound that is formed after the reaction of a acid and a base. A salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid.

Types of salts

Acid salts are formed when only some of the H+ ions are replaced. They contain some H+ ions from the original acid. For example,
NaOH(aq) + H2SO4 (aq)  $\rightarrow$  NaHSO4 (aq) + H2O (l)

                     Acid                      Acid salt

Normal salts

A normal salt is formed when all the H+ ions are replaced. For example,
2NaOH (aq) + H2SO4(aq)  $\rightarrow$  Na2SO4(aq)  + 2H2O (l)

                                                  normal salt