1. A guide for A level students KNOCKHARDY PUBLISHING
ACIDS, BASES
AND SALTS
A guide for A level students
2008 SPECIFICATIONS
KNOCKHARDY PUBLISHING

2. KNOCKHARDY PUBLISHING
ACIDS, BASES AND SALTS
INTRODUCTION
This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards.
Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available.
Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at...
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3. BRØNSTED-LOWRY THEORY
ACIDS AND BASES
BRØNSTED-LOWRY THEORY
ACID proton donor HCl ——> H+(aq) Cl¯(aq)
BASE proton acceptor NH3 (aq) + H+(aq) ——> NH4+(aq)

4. BRØNSTED-LOWRY THEORY
ACIDS AND BASES
BRØNSTED-LOWRY THEORY
ACID proton donor HCl ——> H+(aq) Cl¯(aq)
BASE proton acceptor NH3 (aq) + H+(aq) ——> NH4+(aq)
Conjugate systems
Acids are related to bases ACID PROTON CONJUGATE BASE
Bases are related to acids BASE PROTON CONJUGATE ACID

5. BRØNSTED-LOWRY THEORY
ACIDS AND BASES
BRØNSTED-LOWRY THEORY
ACID proton donor HCl ——> H+(aq) Cl¯(aq)
BASE proton acceptor NH3 (aq) + H+(aq) ——> NH4+(aq)
Conjugate systems
Acids are related to bases ACID PROTON CONJUGATE BASE
Bases are related to acids BASE PROTON CONJUGATE ACID
For an acid to behave as an acid, it must have a base present to accept a proton...
HA B BH A¯
acid base conjugate conjugate
acid base
example CH3COO¯ H2O CH3COOH OH¯
base acid acid base

6. STRONG ACIDS AND BASES STRONG
ACIDS completely dissociate (split up) into ions in aqueous solution
e.g. HCl ——> H+(aq) Cl¯(aq) MONOPROTIC 1 replaceable H
HNO3 ——> H+(aq) NO3¯(aq)
H2SO4 ——> 2H+(aq) SO42-(aq) DIPROTIC 2 replaceable H’s

7. STRONG ACIDS AND BASES STRONG
ACIDS completely dissociate (split up) into ions in aqueous solution
e.g. HCl ——> H+(aq) Cl¯(aq) MONOPROTIC 1 replaceable H
HNO3 ——> H+(aq) NO3¯(aq)
H2SO4 ——> 2H+(aq) SO42-(aq) DIPROTIC 2 replaceable H’s
BASES completely dissociate into ions in aqueous solution
e.g. NaOH(aq) ——> Na+(aq) + OH¯(aq)

8. WEAK ACIDS
Weak acids partially dissociate into ions in aqueous solution
e.g. ethanoic acid CH3COOH(aq) CH3COO¯(aq) H+(aq)
When a weak acid dissolves in
water an equilibrium is set up HA(aq) + H2O(l) A¯(aq) H3O+(aq)
The water stabilises the ions
To make calculations easier
the dissociation can be written... HA(aq) A¯(aq) H+(aq)

9. WEAK ACIDS
Weak acids partially dissociate into ions in aqueous solution
e.g. ethanoic acid CH3COOH(aq) CH3COO¯(aq) H+(aq)
When a weak acid dissolves in
water an equilibrium is set up HA(aq) + H2O(l) A¯(aq) H3O+(aq)
The water stabilises the ions
To make calculations easier
the dissociation can be written... HA(aq) A¯(aq) H+(aq)
The weaker the acid the less it dissociates
the more the equilibrium lies to the left.

10. WEAK BASES
Partially react with water to give ions in aqueous solution e.g. ammonia
When a weak base dissolves in water an equilibrium is set up
NH3 (aq) H2O (l) NH4+ (aq) OH¯ (aq)
as in the case of acids it is more simply written
NH3 (aq) H+ (aq) NH4+ (aq)

11. WEAK BASES
Partially react with water to give ions in aqueous solution e.g. ammonia
When a weak base dissolves in water an equilibrium is set up
NH3 (aq) H2O (l) NH4+ (aq) OH¯ (aq)
as in the case of acids it is more simply written
NH3 (aq) H+ (aq) NH4+ (aq)
The weaker the base the less it dissociates
the more the equilibrium lies to the left
The relative strengths of bases can be expressed as Kb or pKb values.

12. REACTIONS OF HYDROCHLORIC ACID
Is a typical acid in dilute aqueous solution HCl ——> H+ (aq) Cl¯(aq)
Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present.

13. REACTIONS OF HYDROCHLORIC ACID
Is a typical acid in dilute aqueous solution HCl ——> H+ (aq) Cl¯(aq)
Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present.
If the gas is passed into water, the hydrogen chloride molecules dissociate into ions. The solution now conducts electricity showing ions are present. For each hydrogen chloride molecule that dissociates one hydrogen ion and one chloride ion are produced. The solution turns litmus paper red because of the H+(aq) ions.

14. REACTIONS OF HYDROCHLORIC ACID
Is a typical acid in dilute aqueous solution HCl ——> H+ (aq) Cl¯(aq)
Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present.
If the gas is passed into water, the hydrogen chloride molecules dissociate into ions. The solution now conducts electricity showing ions are present. For each hydrogen chloride molecule that dissociates one hydrogen ion and one chloride ion are produced. The solution turns litmus paper red because of the H+(aq) ions.

15. REACTIONS OF HYDROCHLORIC ACID
Is a typical acid in dilute aqueous solution HCl ——> H+ (aq) Cl¯(aq)
HYDROGEN CHLORIDE HYDROCHLORIC ACID
colourless gas Appearance colourless soln.
covalent molecule Bonding aqueous ions
HCl(g) Formula HCl(aq)
poor Conductivity good
no reaction Dry blue litmus goes red

16. REACTIONS OF HYDROCHLORIC ACID
Is a typical acid in dilute aqueous solution HCl ——> H+ (aq) Cl¯(aq)
Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present.
If the gas is passed into water, the hydrogen chloride molecules dissociate into ions. The solution now conducts electricity showing ions are present. For each hydrogen chloride molecule that dissociates one hydrogen ion and one chloride ion are produced. The solution turns litmus paper red because of the H+(aq) ions.
Appearance Bonding and formula Conductivity Dry litmus
hydrogen chloride colourless gas covalent molecule HCl(g) poor no reaction
hydrochloric acid colourless soln aqueous ions HCl(aq) good goes red

17. REACTIONS OF HYDROCHLORIC ACID
Metals magnesium dil. hydrochloric acid ——> magnesium chloride + hydrogen
Mg(s) HCl(aq) ——> MgCl2(aq) H2(g)
WRITE OUT THE BALANCED EQUATION FOR THE REACTION

18. REACTIONS OF HYDROCHLORIC ACID
Metals magnesium dil. hydrochloric acid ——> magnesium chloride + hydrogen
Mg(s) HCl(aq) ——> MgCl2(aq) H2(g)
Mg(s) H+(aq) Cl¯(aq) ——> Mg2+(aq) Cl¯(aq) H2(g)
WRITE OUT THE BALANCED EQUATION FOR THE REACTION
DILUTE ACIDS AND SALTS CONTAIN IONS; WATER, HYDROGEN & CARBON DIOXIDE DON’T

19. REACTIONS OF HYDROCHLORIC ACID
Metals magnesium dil. hydrochloric acid ——> magnesium chloride + hydrogen
Mg(s) HCl(aq) ——> MgCl2(aq) H2(g)
Mg(s) H+(aq) Cl¯(aq) ——> Mg2+(aq) Cl¯(aq) H2(g)
cancel ions Mg(s) H+(aq) ——> Mg2+(aq) H2(g)
WRITE OUT THE BALANCED EQUATION FOR THE REACTION
DILUTE ACIDS AND SALTS CONTAIN IONS; WATER, HYDROGEN & CARBON DIOXIDE DON’T
CANCEL OUT THE IONS WHICH APPEAR ON BOTH SIDES OF THE EQUATION

20. REACTIONS OF HYDROCHLORIC ACID
Metals magnesium dil. hydrochloric acid ——> magnesium chloride + hydrogen
Mg(s) HCl(aq) ——> MgCl2(aq) H2(g)
Mg(s) H+(aq) Cl¯(aq) ——> Mg2+(aq) Cl¯(aq) H2(g)
cancel ions Mg(s) H+(aq) ——> Mg2+(aq) H2(g)
Basic
Oxides copper(II) oxide dil. hydrochloric acid ——> copper(II) chloride water
CuO(s) HCl(aq) ——> CuCl2(aq) H2O(l)
Cu2+O2-(s) H+(aq) Cl¯(aq) ——> Cu 2+ (aq) Cl¯(aq) H2O(l)
cancel ions O H+(aq) ——> H2O(l)

21. REACTIONS OF HYDROCHLORIC ACID
Alkalis sodium hydroxide + dil. hydrochloric acid ——> sodium chloride water
NaOH(aq) HCl(aq) ——> NaCl(aq) H2O(l)
Na+(aq) + OH¯(aq) H+(aq) + Cl¯(aq) ——> Na+ (aq) + Cl¯(aq) H2O(l)
cancel ions H+(aq) + OH¯(aq) ——> H2O(l)

22. REACTIONS OF HYDROCHLORIC ACID
Alkalis sodium hydroxide + dil. hydrochloric acid ——> sodium chloride water
NaOH(aq) HCl(aq) ——> NaCl(aq) H2O(l)
Na+(aq) + OH¯(aq) H+(aq) + Cl¯(aq) ——> Na+ (aq) + Cl¯(aq) H2O(l)
cancel ions H+(aq) + OH¯(aq) ——> H2O(l)
Carbonates calcium carbonate + hydrochloric acid ——> calcium chloride + carbon dioxide + water
CaCO3(s) HCl(aq) ——> CaCl2(aq) CO2(g) + H2O(l)
Ca2+CO32-(s) H+(aq) + 2Cl¯(aq) ——> Ca2+(aq) Cl¯(aq) + CO2(g) H2O(l)
cancel ions CO H+(aq) ——> CO2(g) H2O(l)

23. REACTIONS OF HYDROCHLORIC ACID
Alkalis sodium hydroxide + dil. hydrochloric acid ——> sodium chloride water
NaOH(aq) HCl(aq) ——> NaCl(aq) H2O(l)
Na+(aq) + OH¯(aq) H+(aq) + Cl¯(aq) ——> Na+ (aq) + Cl¯(aq) H2O(l)
cancel ions H+(aq) + OH¯(aq) ——> H2O(l)
Carbonates calcium carbonate + hydrochloric acid ——> calcium chloride + carbon dioxide + water
CaCO3(s) HCl(aq) ——> CaCl2(aq) CO2(g) + H2O(l)
Ca2+CO32-(s) H+(aq) + 2Cl¯(aq) ——> Ca2+(aq) Cl¯(aq) + CO2(g) H2O(l)
cancel ions CO H+(aq) ——> CO2(g) H2O(l)
Hydrogen carbonates H+(aq) + HCO3¯ ——> CO2(g) H2O(l)

24. REACTIONS OF HYDROCHLORIC ACID
SUMMARY
METALS react to give a salt + hydrogen
METAL OXIDES react to give a salt + water
METAL HYDROXIDES react to give a salt + water
CARBONATES react to give a salt + water + carbon dioxide
HYDROGENCARBONATES react to give a salt + water + carbon dioxide
AMMONIA reacts to give an ammonium salt

25. © 2009 JONATHAN HOPTON & KNOCKHARDY PUBLISHING
ACIDS, BASES
AND SALTS
THE END
© 2009 JONATHAN HOPTON & KNOCKHARDY PUBLISHING