Acids, Alkalis and Bases CGP topic 3
Acid à a substance that releases H+ ions when added to water
Alkalis àa substance that releases OH- ions when added to water Not all bases are alkali but all
Bases à a substance that reacts with acids to form a salt and water alkalis are soluble bases.
Acids Alkalis
• Nitric acid • Potassium hydroxide
• Phosphoric acid • Ammonia
• Hydrochloric acid • Sodium hydroxide
• Sulphuric acid
Acids are substances that can donate H+ ions to bases so it is a proton donor and a base is a proton
acceptor
Hydrogen ignites in air. If hydrogen is present in a test
tube, a lighted splint held near its mouth ignites with a Oxygen supports combustion. If oxygen is present in a
squeaky pop test tube, a glowing splint relights when it is held inside.
Carbon dioxide reacts with calcium hydroxide solution to produce a white precipitate
of calcium carbonate. Limewater is a solution of calcium hydroxide. If carbon dioxide is
bubbled through limewater, the limewater turns milky or cloudy white.
A neutralization reaction is when an acid and a base react to form water and a salt and involves the
combination of H+ ions and OH- ions to generate water.
pH
pH is a measure of the concentration of H+ ions in a
solution. Therefore, the more hydrogen ions present,
the lower the pH and vice versa.
pH is a log scale:
- pH 1 has a H+ concentration 10x more than pH 2
- pH 9 has a H+ concentration 10x lower than pH 8
Indicator Acidic Neutral Alkaline
Methyl orange Red Yellow Yellow
Phenolphthalein Colourless Colourless Pink
, Strong and weak acids
Acids in solution are a source of hydrogen ions, H+. The hydrogen ions are produced when the acid
dissociates or breaks down to form ions.
Weak acids
Strong acids
Weak acids only partially ionise in water.
Strong acids completely ionise in water.
E.g. ethanoic acid only partially ionised to form
E.g. HCL ionises completely to form hydrogen ions hydrogen ions and ethanoate ions:
and chloride ions:
CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq)
+ -
HCl(aq) → H (aq) + Cl (aq)
The ⇌ symbol shows that it is a reversible reaction and
Nitric acid and sulfuric acid are also strong acids. does not go to completion.
A concentrated acid contains a large amount of acid in a
given volume; a dilute acid contains a small amount
of acid in a given volume.
Acid Type of salt
Hydrochloric acid (HCL) Chloride
Sulfuric acid (H2SO4) Sulphate
Nitric acid (HNO3) Nitrate
Acid à a substance that releases H+ ions when added to water
Alkalis àa substance that releases OH- ions when added to water Not all bases are alkali but all
Bases à a substance that reacts with acids to form a salt and water alkalis are soluble bases.
Acids Alkalis
• Nitric acid • Potassium hydroxide
• Phosphoric acid • Ammonia
• Hydrochloric acid • Sodium hydroxide
• Sulphuric acid
Acids are substances that can donate H+ ions to bases so it is a proton donor and a base is a proton
acceptor
Hydrogen ignites in air. If hydrogen is present in a test
tube, a lighted splint held near its mouth ignites with a Oxygen supports combustion. If oxygen is present in a
squeaky pop test tube, a glowing splint relights when it is held inside.
Carbon dioxide reacts with calcium hydroxide solution to produce a white precipitate
of calcium carbonate. Limewater is a solution of calcium hydroxide. If carbon dioxide is
bubbled through limewater, the limewater turns milky or cloudy white.
A neutralization reaction is when an acid and a base react to form water and a salt and involves the
combination of H+ ions and OH- ions to generate water.
pH
pH is a measure of the concentration of H+ ions in a
solution. Therefore, the more hydrogen ions present,
the lower the pH and vice versa.
pH is a log scale:
- pH 1 has a H+ concentration 10x more than pH 2
- pH 9 has a H+ concentration 10x lower than pH 8
Indicator Acidic Neutral Alkaline
Methyl orange Red Yellow Yellow
Phenolphthalein Colourless Colourless Pink
, Strong and weak acids
Acids in solution are a source of hydrogen ions, H+. The hydrogen ions are produced when the acid
dissociates or breaks down to form ions.
Weak acids
Strong acids
Weak acids only partially ionise in water.
Strong acids completely ionise in water.
E.g. ethanoic acid only partially ionised to form
E.g. HCL ionises completely to form hydrogen ions hydrogen ions and ethanoate ions:
and chloride ions:
CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq)
+ -
HCl(aq) → H (aq) + Cl (aq)
The ⇌ symbol shows that it is a reversible reaction and
Nitric acid and sulfuric acid are also strong acids. does not go to completion.
A concentrated acid contains a large amount of acid in a
given volume; a dilute acid contains a small amount
of acid in a given volume.
Acid Type of salt
Hydrochloric acid (HCL) Chloride
Sulfuric acid (H2SO4) Sulphate
Nitric acid (HNO3) Nitrate
