Acids, Bases & Salts

Page
9

Slide 40

Topic 10: ACIDS, BASES & SALTS

40

The pH scale is a measure of the relative acidity or alkalinity of a solution.

It is defined as negative log of H+ ion concentration.

pH = -log [H+]

Water is a neutral liquid with a pH of 7 (green). When a substance dissolves in water it forms an aqueous solution that may be acidic, neutral or alkaline.

Acidic solutions have a pH of less than 7, and the lower the number, the stronger the acid is

Neutral solutions have a pH of 7. These are quite often solutions of salts, which are themselves formed from neutralizing acids and bases.

Alkaline solutions have a pH of over 7 and the higher the pH the stronger is the alkali. Weak alkalis like ammonia give a pH of 10-11 but strong alkalis like sodium hydroxide give a pH of 13-14.

جمعرات، 28 ربیع الثانی، 1438

Slide 41

pH

A change of 1 in pH is a tenfold increase in acid or base strength.

A pH of 4 is 10 times more acidic than a pH of 5.

A pH of 12 is 100 times more basic than a pH of 10.

جمعرات، 28 ربیع الثانی، 1438

Topic 10: ACIDS, BASES & SALTS

41

Slide 42

Topic 10: ACIDS, BASES & SALTS

42

جمعرات، 28 ربیع الثانی، 1438

Slide 43

Topic 10: ACIDS, BASES & SALTS

43

INDICATORS.

Indicators are the substances that have different colors in acidic and in alkaline solution.

جمعرات، 28 ربیع الثانی، 1438

Slide 44

Topic 10: ACIDS, BASES & SALTS

44

جمعرات، 28 ربیع الثانی، 1438

Slide 45

pH Graph

Topic 10: ACIDS, BASES & SALTS

45

جمعرات، 28 ربیع الثانی، 1438

Slide 46

IONIC EQUATIONS

Topic 10: ACIDS, BASES & SALTS

46

In many reactions only certain ions change their 'chemical state' but other ions remain in exactly the same original physical and chemical state.