lOMoAR cPSD| 23050439
MODULE 6: Acid/BAse
Reactions
Properties of Acids and Bases
Inquiry Question: What is an acid and what is a base?
IUPAC Nomenclature and Properties of Common Inorganic
Acids and Bases
Common Properties of Acids
● Sour taste
● Stinging or burning sensation upon contact with skin
● Conducts electricity when dissolved in solution (electrolyte) (H+/H3O+) ● Turns blue
litmus red and red litmus remains red
E.g: HCl, H2SO4, HNO3, CH3COOHs, CO2
Common Properties of Bases
● Slippery/soapy feel
● Bitter taste
● Conducts electricity when dissolved in solution (electrolyte) (OH-) ● Turns red litmus
blue and blue litmus remains blue
Soluble bases in water are called alkalis
E.g: NaOH, Na2O, NaHCO3, NH3
,Neutral compounds: Water/H2O, doesn’t affect litmus paper, harmless
Investigation of the Preparation and Use of Indicators
Indicators
● Used to qualitatively estimate the pH range of an acid or base
● Change colour depending on the pH of a solution
Indicators as Weak Acid/Bases
● Indicators are generally weak acids (or weak bases)
● Weak acids will not ionise completely in solution, but instead exist in equilibrium
○ HIn(aq) + H2O(l) ←→ H3O+(aq) + In-(aq)
○ HIn molecule represents some weak monoprotic acid, that has a different colour
than its conjugate base In-
● Typically, one or both of the species are intensely coloured so only a small amount of
indicator is needed, small enough that the pH of the solution being tested is essentially
unaffected
○ Water and hydronium are considered colourless
○ The observed colour is of the species that is at least 10 fold greater in concentration
Products of Acid Reactions
Acids and Bases (Neutralisation)
Acid + Base → Salt + Water
E.g: HCl + NaOH → NaCl + H2O
Acids and Carbonates
Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
E.g: 2HCl + Na2CO3 → 2NaCl + H2O + CO2
, lOMoAR cPSD| 23050439
Acids and Metal
Acid + Metal → Salt + Hydrogen Gas (MASH)
E.g: 2HCl + 2Na → 2NaCl + H2
Applications of Neutralisation Reactions in Everyday Life
and Industrial Processes
Applications of Neutralisation
● Acid spills on ground can corrode carpet and tile and damage skin upon contact
● When handling strong acids or bases
○ Use gloves and goggles to protect hands and eyes against acid spills
○ Closed shoes to protect feet against acid spills
○ Lab coat to protect clothes and body against acid spills
○ Have eye wash and rinsing sink nearby in case of acid spills and acid splashes into
eyes
○ Have a weak base nearby in order to neutralise acid spills
● Acid/base spills are cleaned by neutralisation reaction with an appropriate reactant
○ Solid sodium hydrogen carbonate used
■ As a solid, it helps contain an acid spill rather than increase size of spill
■ As a weak base, it will minimise heat released in a neutralisation reaction
■ As a carbonate, it will react with acid to produce CO2 in addition to salt and
water, and by producing more reactants, heat energy released from a
neutralisation reaction is reduced since some heat energy is stored in the
chemical bonds of CO2
○ Strong bases are never used to neutralise an acid spill because of the highly
exothermic nature of the reaction
■ Excess heat energy can cause damage to underlying surfaces of the acid
spill
Strong Acid Hazards
● Corrosive irritant to skin, eyes and lungs
● Toxic to kidneys, lungs, heart, upper respiratory tract, eyes, organ damage
, Strong Base Hazards
● Irritant to skin, eyes and lungs
● Repeated or prolonged exposure can damage organs
Practical Investigation to Measure Enthalpy of
Neutralisation
Enthalpy of Neutralisation
● Neutralisation reactions are exothermic
● Strong acid and base neutralisation
○ Completely ionise in solution forming OH- and H3O+
○ When they are reacted, these ions react, forming water
○ H3O+(aq) + OH-(aq) → H2O(l) ΔHneut =− 7.95 kJmol−1
● Weak acid or base neutralisation
○ Do not ionise completely in water
○ Ionisation of weak acid or base in water is endothermic
○ Enthalpy of neutralisation is unique for each weak acid or base
E.g. CH3COOH(aq) + H2O(l) ←→ CH3COO-(aq) + H3O+(aq) ΔHionisation = + 1.2kJmol−1
● When a strong base is added to this solution, the hydronium ions are neutralised by the
hydroxide ions which causes the above reaction to shift right (LCP)
● Adding excess hydroxide ions drives equilibrium to completion
● In the neutralisation of acetic acid, there are 2 equations occurring
CH3COOH(aq) + H2O(l) ←→ CH3COO-(aq) + H3O+(aq) ΔH1 = + 1.2kJmol−1
H3O+(aq) + OH-(aq) → H2O(l) ΔH2 =− 7.95 kJmol−1
We can use Hess’s Law to calculate enthalpy of neutralisation of a weak acid and a strong base
● Add H1 and H2
The enthalpy of neutralisation involving a weak acid, or a weak base will be smaller in
magnitude than that of a strong acid and strong base
Weak Acid and Strong Base - Strong base has to wait for Weak acid to ionise
MODULE 6: Acid/BAse
Reactions
Properties of Acids and Bases
Inquiry Question: What is an acid and what is a base?
IUPAC Nomenclature and Properties of Common Inorganic
Acids and Bases
Common Properties of Acids
● Sour taste
● Stinging or burning sensation upon contact with skin
● Conducts electricity when dissolved in solution (electrolyte) (H+/H3O+) ● Turns blue
litmus red and red litmus remains red
E.g: HCl, H2SO4, HNO3, CH3COOHs, CO2
Common Properties of Bases
● Slippery/soapy feel
● Bitter taste
● Conducts electricity when dissolved in solution (electrolyte) (OH-) ● Turns red litmus
blue and blue litmus remains blue
Soluble bases in water are called alkalis
E.g: NaOH, Na2O, NaHCO3, NH3
,Neutral compounds: Water/H2O, doesn’t affect litmus paper, harmless
Investigation of the Preparation and Use of Indicators
Indicators
● Used to qualitatively estimate the pH range of an acid or base
● Change colour depending on the pH of a solution
Indicators as Weak Acid/Bases
● Indicators are generally weak acids (or weak bases)
● Weak acids will not ionise completely in solution, but instead exist in equilibrium
○ HIn(aq) + H2O(l) ←→ H3O+(aq) + In-(aq)
○ HIn molecule represents some weak monoprotic acid, that has a different colour
than its conjugate base In-
● Typically, one or both of the species are intensely coloured so only a small amount of
indicator is needed, small enough that the pH of the solution being tested is essentially
unaffected
○ Water and hydronium are considered colourless
○ The observed colour is of the species that is at least 10 fold greater in concentration
Products of Acid Reactions
Acids and Bases (Neutralisation)
Acid + Base → Salt + Water
E.g: HCl + NaOH → NaCl + H2O
Acids and Carbonates
Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
E.g: 2HCl + Na2CO3 → 2NaCl + H2O + CO2
, lOMoAR cPSD| 23050439
Acids and Metal
Acid + Metal → Salt + Hydrogen Gas (MASH)
E.g: 2HCl + 2Na → 2NaCl + H2
Applications of Neutralisation Reactions in Everyday Life
and Industrial Processes
Applications of Neutralisation
● Acid spills on ground can corrode carpet and tile and damage skin upon contact
● When handling strong acids or bases
○ Use gloves and goggles to protect hands and eyes against acid spills
○ Closed shoes to protect feet against acid spills
○ Lab coat to protect clothes and body against acid spills
○ Have eye wash and rinsing sink nearby in case of acid spills and acid splashes into
eyes
○ Have a weak base nearby in order to neutralise acid spills
● Acid/base spills are cleaned by neutralisation reaction with an appropriate reactant
○ Solid sodium hydrogen carbonate used
■ As a solid, it helps contain an acid spill rather than increase size of spill
■ As a weak base, it will minimise heat released in a neutralisation reaction
■ As a carbonate, it will react with acid to produce CO2 in addition to salt and
water, and by producing more reactants, heat energy released from a
neutralisation reaction is reduced since some heat energy is stored in the
chemical bonds of CO2
○ Strong bases are never used to neutralise an acid spill because of the highly
exothermic nature of the reaction
■ Excess heat energy can cause damage to underlying surfaces of the acid
spill
Strong Acid Hazards
● Corrosive irritant to skin, eyes and lungs
● Toxic to kidneys, lungs, heart, upper respiratory tract, eyes, organ damage
, Strong Base Hazards
● Irritant to skin, eyes and lungs
● Repeated or prolonged exposure can damage organs
Practical Investigation to Measure Enthalpy of
Neutralisation
Enthalpy of Neutralisation
● Neutralisation reactions are exothermic
● Strong acid and base neutralisation
○ Completely ionise in solution forming OH- and H3O+
○ When they are reacted, these ions react, forming water
○ H3O+(aq) + OH-(aq) → H2O(l) ΔHneut =− 7.95 kJmol−1
● Weak acid or base neutralisation
○ Do not ionise completely in water
○ Ionisation of weak acid or base in water is endothermic
○ Enthalpy of neutralisation is unique for each weak acid or base
E.g. CH3COOH(aq) + H2O(l) ←→ CH3COO-(aq) + H3O+(aq) ΔHionisation = + 1.2kJmol−1
● When a strong base is added to this solution, the hydronium ions are neutralised by the
hydroxide ions which causes the above reaction to shift right (LCP)
● Adding excess hydroxide ions drives equilibrium to completion
● In the neutralisation of acetic acid, there are 2 equations occurring
CH3COOH(aq) + H2O(l) ←→ CH3COO-(aq) + H3O+(aq) ΔH1 = + 1.2kJmol−1
H3O+(aq) + OH-(aq) → H2O(l) ΔH2 =− 7.95 kJmol−1
We can use Hess’s Law to calculate enthalpy of neutralisation of a weak acid and a strong base
● Add H1 and H2
The enthalpy of neutralisation involving a weak acid, or a weak base will be smaller in
magnitude than that of a strong acid and strong base
Weak Acid and Strong Base - Strong base has to wait for Weak acid to ionise
