This document provides information about acids and bases: - Acids are substances that produce hydrogen ions in water and have properties like a sour taste and turning litmus paper red. Strong acids fully ionize in water while weak acids only partially ionize. - Bases include metal oxides and hydroxides. Soluble bases are called alkalis. Bases react with acids to produce salt and water in a neutralization reaction. - Important acids and bases have many applications from batteries to cleaning to food preservation. Processes like the Contact Process are used industrially to produce acids like sulfuric acid.

1. Chemistry Notes

2. Acids
• An acid is a substance that produces hydrogen ions
when dissolved in water.
• All acids contain hydrogen. But not all substances with
hydrogen contains acids (Water).
• The hydrogen ions produced are responsible for the
properties of an acid.
• A strong acid is one that is completely ionized in water
(eg HCl) whereas a weak acid is only partially ionized in
water
o Strong acids: Sulphuric acid, Nitric acid, Hydrochloric
acid, Carbonic acid, Sulphurous acid, Phosphoric acid
o Weak acids: Ethanoic acid, Methanoic acid, Lactic acid,
Citric acid

3. Properties of Acids
• Acids have a sour taste eg vinegar
• Acids are electrolytes because they dissolve in
water to form ions which conduct electricity.
• Acids turn blue litmus paper red.
• pH value < 7.
• If concentrated they can be corrosive

4. Some common acids
• Artificial
o Hydrochloric Acid (HCl)
o Sulphuric Acid (H2SO4)
o Nitric Acid (HNO3)
• Natural
o Ethanoic Acid (Found in vinegar)

5. Chemical Properties of
Acids
1.Acids react with reactive metals to form
hydrogen gas and a salt.
• Formula: Metal + Acid Salt + Hydrogen
• Reactive metals give out electrons easily to form positive
ions.
• Example: Magnesium Ribbon with Dilute sulphuric acid.
Equation:
o Mg (s) + (H2SO4) (aq) MgSO4 (aq) + H2 (g)

6. Chemical Properties of
Acids
• To test for hydrogen, place a lighted splint at the test
tube and a “pop sound” will be heard.
• Some acid and metal reactions which do not give
hydrogen:
o Unreactive metals (copper and silver)
o Concentrated nitric acid reacts with metals but it does
not give hydrogen (gives nitrogen dioxide)
o Lead does not react as a coating is formed once lead is
placed inside the acid.

7. Chemical Properties of
Acids
2. Acids react with carbonates to form a salt,
carbon dioxide and water.
• Equation: Acid + Carbonate Salt + Carbon Dioxide
+ Water
• Example: Sodium Carbonate + Dilute hydrochloric
acid Sodium Chloride + Water + Carbon Dioxide
• Bubble the gas through limewater to test for carbon
dioxide.

8. Chemical Properties of
Acids
1.Acids react with metal oxides and
hydroxides (Insoluble bases) to form salt
and water.
• General Equations:
Metal Oxide + Acid Salt and Water.
Metal Hydroxide + Acid Salt and Water

9. • Acids only react when placed into water.
This is because water can break apart the acid into
hydrogen ions and a salt.
• Therefore, an acid dissociate in water to produce
hydrogen ions which are responsible for the acidic
properties.
• Acids only show their properties when dissolved in water.
• The hydrogen ions produced are not hydrogen gas.
• They react with metals like magnesium to produce
hydrogen gas and magnesium ions.
• A few drops of water is enough to allow an acid to
dissociate.
Acidity and Water

10. • Sulphuric Acid:
o Detergents
o Car Batteries
• Ethanoic Acid:
o Vinegar to preserve food
o Adhesives (glue)
• Hydrochloric acid
o Cleaning metals
o Leather processing
Uses of acids

11. Uses of Sulphuric acid &
Sulphur dioxide
• Sulphuric acid used to
o Electrolyte in lead-acid batteries
o Production of fertilizers such as ammonium sulphate,
potassium sulphate, and calcium sulphate
o Manufacture non-soapy detergents
o Make artificial silks like rayon
o Remove oxide from iron and steel before galvanising or
electroplating
• Sulphur dioxide used to
o Manufacture sulphurous acid H2SO3
o Manufacture sulphuric acid H2SO4
o Use as preservative
o Used to sterilize things
o Used to bleach wood pulp before making paper

12. Sulphur
• Sulphur exists as S8 molecule in which 8 atoms of sulphur join
together by covalent bonding
o Weak van der Wal’s forces between sulphur molecules so sulphur
has low melting and boiling point
• Sources of sulphur
 Volcanic regions
 Natural gas and crude oil
 Minerals
• Oxides of sulphur
o Sulphur dioxide SO2
 S (s) + O2 (g) -- > SO2 (g)
 An acidic gas with choking smell
o Sulphur trioxide SO3
 2SO2 (g) + O2 (g) < --- > 2SO3 (g)

13. Manufacture of Sulphuric
acid by Contact Process
• The Contact Process is the current method of
producing sulphuric acid in high concentrations
needed for industrial processes
o Catalyst: Vanadium(V) oxide

14. Contact Process Steps
1. Sulphur dioxide produced by burning sulphur
o S (s) + O2 (g) -- > SO2 (g)
2. Sulphur dioxide is purified
3. Sulphur dioxide reacted with oxygen over vanadium(V) oxide catalyst
o 2SO2 (g) + O2 (g) < ---- > 2SO3 (g)
o Reaction is exothermic so it favors a low temperature for high yield of
SO2
o But if temperature lowered, rate of reaction slows down so average
temperature of 450oC used
o Pressure kept at 2ATM
4. Sulphur trioxide dissolved in concentrates sulphuric acid to form oleum
1. SO3 (g) + H2SO4 (l) -- > H2S2O7 (l)
5. Oleum diluted with water to form sulphuric acid
1. H2SO4 (l) + H2O (l) -- > 2H2SO4 (l)

15. • Bases are metal oxides and hydroxides
• Soluble bases are known as alkalis
• A base is a substance that reacts with an acid to
give salt and water only --- neutralization reaction
• Acid + Base Salt and Water
Similar to: Acid + Metal Oxide/Hydroxide Salt and
Water.
• Ionic Equation for this is always:
OH- + H+ H2O (l)
Bases

16. • Sodium Oxide
• Zinc Oxide
• Copper (II) Oxide
• Magnesium Hydroxide
• Aluminum Hydroxide
Common Bases

17. Family of Bases

18. Alkalis
• An alkali is a base that is soluble in water.
• Some examples include:
o Sodium Hydroxide
o Potassium Hydroxide
o Calcium Hydroxide
o Barium Hydroxide
o Aqueous Ammonia

19. Properties of Alkalis
• Alkalis have a bitter taste and soapy feel.
• Alkalis turn red litmus paper blue.
• pH value > 7.

20. • All alkalis produce hydroxide ions when
dissolved in water.
• Example: Sodium Hydroxide + Water Sodium
Ion + Hydroxide ion.
Chemical Properties of
Alkalis

21. • All alkalis react with acids to form salt and water
only.
o This is also known as neutralization.
• In neutralization, the hydrogen ions from the acid
react with the hydroxide ions of the alkali
o Neutralization reactions are exothermic
• The salt depends on the acid used.
o Sulphuric Acid Sulphide
o Hydrochloric Acid Chloride
• The ionic equation for this is standardized.
o H+ (aq) + OH- (aq) H2O (l).
Neutralization

22. Applications of
Neutralization
1. Soil treatment – farming
• Most plants grow best at pH 7. If the soil is acidic or
alkaline the plant may grow badly.
• Therefore, chemicals can be added to the soil to
change its pH.
• If the soil is too acidic - the most common complaint - it
is treated with a base (chemicals opposite to an acid) in
order to neutralize it.
• Common treatments use quicklime (calcium oxide) or
chalk (calcium carbonate).

23. 2. Indigestion
• We all have hydrochloric acid in our stomach - it
helps breakdown food
• However, too much acid leads to indigestion.
• Therefore, to cure this ailment we need to neutralize
the acid with a base such as, sodium hydrogen
carbonate (baking soda), or an indigestion tablet.
Applications of
Neutralization

24. Applications of
Neutralization
3. Insect stings
• A bee sting contains acid.
• To relieve the painful symptoms of the sting we need to
neutralize the acid. By rubbing on calamine lotion (zinc
carbonate) or baking soda the acid can be neutralized.
• Wasp stings are alkaline, hence acid is needed to
neutralize and remove the painful sting.
• Vinegar (ethanoic acid) is used.

25. 1. Alkalis heated with ammonium salts gives
off ammonia gas.
• General Equation: Alkali + Ammonium Salt
Ammonia + Water + Salt.
• Ammonia has a strong smell and turn red litmus
paper blue.
• Example: Calcium hydroxide + Ammonium chloride
-- > Calcium Chloride + Water + Ammonia.
Chemical properties of
alkalis

26. 2. Alkalis can react with the solution of 1 metal
salt to give metal hydroxide and another metal
salt.
• General Equation: Alkali + Salt (of metal A) --> Metal
Hydroxide + Salt (of metal B)
• Example: Sodium Hydroxide + Iron (II) Sulphate -->
Iron (II) Hydroxide + Sodium Sulphate.
Chemical properties of
alkalis

27. Some common alkalis and
bases
Type Common name Chemical name Formula
Alkalis Caustic soda Sodium hydroxide NaOH
Caustic potash Potassium
hydroxide
KOH
Ammonia
solution
Aqueous
ammonia
NH3 (aq)
Bases Slaked lime Calcium
hydroxide
Ca(OH)2
Milk of magnesia Magnesium oxide MgO
Verdigris Copper(II) oxide CuO
Rust Iron(III) oxide Fe2O3

28. • Ammonia Solution:
o Window cleaning solutions
• Calcium Oxide:
o To make iron, concrete, cement
• Magnesium Hydroxide:
o Toothpaste to neutralise acid o teeth
o In antacids to relieve indigestion.
• Sodium Hydroxide:
o In making soaps and detergents.
Uses of alkalis

29. Uses of Ammonia
• Ammonia is important in
o Manufacture nitric acid which is made by the
catalytic oxidation of ammonia over heated platinum
o Producing fertilizers to supply nitrogen that is
essential for plant growth
 Eg ammonium sulphate, ammonium nitrate, urea
 To reduce acidity of soil, better not to add calcium
hydroxide to soil as it can cause the loss of nitrogen
from nitrogenous fertilisers

30. Haber Process
• Haber Process mass produces ammonia by passing nitrogen gas and
hydrogen gas through iron catalyst
• Reversible reaction:
o N2 + 3H2 < ------ > 2NH3
• Exothermic reaction
• Increase in pressure will increase
o the yield of ammonia because in forward reaction, less number of moles
are formed
o Rate of reaction because of more effective collisions so pressure is kept
high at 200 ATM
• Temperature
o Raising temperature of the system will favor the backward reaction
o Lowering temperature will favor ammonia production
o However, at low temperature, the reaction will be very slow which is not
economical, so temperature is kept optimum at 540oC

31. • Concentration tells us how much of a substance is
dissolved in 1dm3 of a solution.
• It can be changed by either adding more solute or more
solvent.
Concentration

32. • Strength refers to how easily an acid or alkali dissociates when
dissolved in water.
• A strong acid like hydrochloric acid dissociates easily in water
(almost 100% of the acid dissociates)
• A weak acid like ethanoic acid does not fully dissociate when
dissolved in water.
• The strength of an acid cannot be changed.
• No matter how concentrated ethanoic acid is, it is still a weak
acid.
• The strength of an acid of an alkali can be shown using the pH
scale.
Strength of acid/alkali

33. pH indicators
• Indicators are substances that turn to different colors in
acidic and alkali solutions
• The pH of a solution is a number that shows how acidic or
alkaline a solution is
o A neutral solution like ethanol has a pH of 7
o An acidic solution like HCl has a pH of 2
o An alkaline solution like NaOH has a pH of 14
• The lower the pH, the more acidic; the higher the pH, the
more alkaline the substance is
• Farmers neutralize excess acidity in the soil by adding
calcium hydroxide (slaked lime) to the soil

34. Preparation of Salts
1. Insoluble salts are prepared using the
precipitation method
o Mixing 2 soluble salts and obtain insoluble salt
through filtration
2. Soluble salts are prepared using acid + excess
metal/insoluble metal oxide/carbonate (if reacting
with insoluble substance) or titration (acid + alkali
reaction)
3. After getting the salt solution, saturate it and then
let it crystallize to get the salt

35. Preparation of salts -
summary

36. Titration
Preparation of NaCl
• Titrate NaOH against HCl
o Pipette 25.0cm3 of HCl into a conical flask
o Add a few drops of indicator (phenolphthalein)
o Add NaOH dropwise to the conical flask until end
point (when 1 drop of NaOH turns permanent pink)
• Heat the resulting solution to dryness
o NaCl is stable to heat

37. Metal oxide/carbonates &
Acids
Preparation of Copper(II) Sulphate
• To 25.0cm3 of sulphuric acid, add CaO or CaCO3 until it
is in excess
o Some excess solid will remain at the bottom
• Filter the mixture
• For the filtrate, warm the solution to half its solution
o Concentration of solution increases
• After crystals form, wash with distilled water and dry it
o Do not heat to dryness as copper sulphate is not
stable to heating

38. Precipitation
Preparation of Barium Sulphate
• Mix two soluble salt to obtain the insoluble salt
o Barium nitrate with sodium sulphate
• Filter the mixture
• Wash the precipitate with distilled water
• Dry using filter paper

39. Aqueous
cation
Addition of dilute NaOH Addition of dilute NH3
Few drops Excess Few drops Excess
Al3+ White
precipitate
Precipitate dissolves
Colorless solution
White
precipitate
Precipitate insoluble
Pb2+ White
precipitate
Precipitate dissolves
Colorless solution
White
precipitate
White precipitate
Zn2+ White
precipitate
Precipitate dissolves
Colorless solution
White
precipitate
Precipitate dissolves
Colorless solution
Ca2+ White
precipitate
Precipitate insoluble No reaction No reaction
Cu3+ Blue
precipitate
Precipitate insoluble Blue
precipitate
Precipitate dissolves
Fe2+ Green
precipitate
Precipitate insoluble Green
precipitate
Precipitate insoluble
Fe3+ Brown
precipitate
Precipitate insoluble Brown
precipitate
Precipitate insoluble
NH4
+ Ammonia gas produced on warming
with dilute NaOH. Gas has a pungent
smell and turns damp red litmus blue
No reaction No reaction
Identification of cations