2. Learning Outcome
• State the use of a ph scale correctly
• Relate pH value with acidic or alkaline properties of a
substance.
• Relate concentration of hydrogen ions with ph value and
concentration of hydroxide ions with ph value.
• Relate strong or weak acid with degree of dissociation
• Relate strong or weak alkali with degree of dissociation
• Conceptualise qualitatively strong and weak acids
• Conceptualise qualitatively strong and weak alkalis.
3.
4. Indicator Colour
Acid Neutral Alkali
Litmus Solution Red Purple Blue
Phenolphthalein Colourless Colourless Pink
Methyl orange Red Orange Yellow
Universal Red Green Purple
indicator
6. STRONG ACID WEAK ACID
Has a high degree of ionization Has a low degree of ionisation
(ionised completely). (partially ionized)
Has a higher concentration of Has a lower concentration of
hydrogen ions. hydrogen ions.
Has a lower pH value. Has a higher pH value.
H2O
H2O
Ex: HCl (l) H+ (aq) + Cl- Ex: CH3COOH (aq) H+ (aq) + CH3COO- (aq)
Degree of ionization a measurement of the percentage
of total number of acids molecules that will ionize
when it dissolve in water.
7. STRONG ALKALI WEAK ALKALI
Has a high degree of ionization Has a low degree of ionisation
(ionised completely). (partially ionized)
Has a higher [OH-]. Has a lower [OH-]
Has a higher pH value. Has a lower pH value.
H2O H2O
Ex: NaOH (l) Na+(aq) + OH- (aq) Ex: Mg(OH)2 (aq) Mg2+ (aq) + OH- (aq)