Chemistry Notes Chapter 6

CHAPTER 6
ACID, BASE AND SALT

6.1 THE ROLE OF WATER IN SHOWING
ACIDIC AND ALKALINE PROPERTIES

Acids EXAMPLE

Chemical substances ionise in water HCL(aq) --> H+(aq) + Cl-(aq)
to produce hydrogen ions, H+
HNO3(aq) --> H+(aq) + NO3-(aq)

Basicity of Acids

Number of hydrogen ions, H+ that can
be produced by an acid molecule that

ionises in water

mONOPROTIC DIPROTIC TRIPROTIC
ACID ACID ACID

Hydrochloric Sulphuric acid, Phosphoric acid,
acid, HCl H2SO4 produces H3PO4 produces
two H+ ions per three H+ ions per
produces one H+
ion per acid acid molecule acid molecule
molecule

Base Alkalis

A substance that reacts with acids Chemical substances that
to produce salt and water only ionise in water to produce

EXAMPLE hydroxide ions, OH-

Metal oxides & EXAMPLE
hydroxides
Metal oxides &
hydroxides

EXAMPLE og base

MgO(s) + H2SO4(aq) --> MgSO4(aq) + H2O(l)

Ca(OH)2(aq) + 2HNO3(aq) --> Ca(NO3)2(aq) + 2H2O(l)

When ammonia gas is dissolved in water

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

USES OF ACIDS, BASES AND ALKALIS

Battery: Used to Toothtpaste: neutralise
power things acid on teeth

Lemon: as Bleach: remove stains from
preserving agent fabric

Vinegar: Used to Soap: as cleansing
make pickles products

The Role of Water to Show Acidity and Alkalinity

Acids Alkalis

Acid only show acidic Alkalis only shows alkaline
properties in the properties when they are
presence of water
dissolved in water

6.2 PH VALUE MEASURE OF
CONCENTRATION OF
HYDROGEN IONS IN AN
AQUEOUS SOLUTION

pH = -log [H+]

Concentration of hydrogen ions, VALUE OF pOH
H+ (increase), pH value (decrease)
pOH = -log [OH-]
Concentration of hydroxide ions,
OH- (increase), pH value (decrease) pH VALUE OF AN ALKALI

pH + pOH = 14
pH = 14 - pOH

TESTED WITH
UNIVERSAL
INDICAOR