Acids

• All acids contain hydrogen in their formulae
• When dissolved in water, an acid releases hydrogen ions as protons 

HCl (g) + aq -> H+(aq) + Cl-(aq)

Strong acids:

• releases all its hydrogen atoms into solution as protons= completely dissociates

HCl -> H+ + Cl-

Weak acids: 

• CH3COOH (aq) -> H+ (aq) + CH3COO- (aq) 

Not all compounds that contain hydrogen are acids and only the hydrogens in the relevant functional group will dissociate. Lots of organic acids are weak. 

Bases: 

• Metal oxides (MgO, CaO, CuO)
• Metal hydroxides 
• Metal carbonates (Na2CO3, CaCO3, CuCO3) 
• Ammonia 

A BASE NEUTRALISES AN ACID TO FORM A SALT

ALKALI: A BASE THAT DISSOLVES IN WATER RELEASING HYDROXIDE IONS INTO THE SOLUTION 

NaOH(s) + aq -> Na+ (aq) + OH- (aq) 

Alkali examples: NaOH, KOH, NH3

In the neutralisation of an acid, H+ ions react with a base to form a salt and water.

The H+ ions from the acid are replaced by metal or ammonium ions from the base. 

Metal oxides and hydroxides are neutralised to produce salt and water only.

CuO (s) + H2SO4 (aq)-> CuSO4 (aq) + H2O(l)

CuO(s)  + 2HCl(aq) -> CuCl2 (aq)  + H2O (l) 

Alkalis: the reactants are in solution 

acid + alkali -> salt + water 

Ionic equation: H+(aq) +OH- (aq) -> H20 (l) 

Acid + carbonate -> salt + carbon dioxide

ZnCO3 (s) + H2S04(aq) -> ZnSO4 (aq) + H2O (l) +CO2 (g)

MgCO3 (s) + 2HCl (aq) -> MgCl2 (aq) +H20 (l) + CO2 (g) 

Dissociation in sulfuric acid:

• H2SO4 is a strong acid but only for one of the hydrogen atoms
• When mixed w water each molecule dissociates, releasing just one of two hydrogen atoms

H2SO4 (aq) -> H+ (aq) + HSO4- (aq) 

• The resulting HS04- (aq) then only partially dissociates

HSO4- -> H+ (aq) + SO4 2- (aq)

Titration- a technique used to accurately measure the volume of one solution that reacts exactly w another solution 

Used for:

• finding the conc. of a substance
• identification of chemicals
• finding purity of a substance

Checking purity is an important part of quality control, especially for medicines, food and cosmetics. 

1) Weigh mass of solid

2) dissolve in small amount of solvent

3) transfer to volumetric flask

4) rinse out beaker and funnel with distilled water several times

5) add distilled water until approximately 1cm below the line

6) add distilled water dropwise until the meniscus sits on the line

7) stopper and invert 

A solution of acid is titrated against a solution of a base using a pipette and a burette.

Typical tolerances:

• 10cm3 pipette : +/- 0.04cm3
• 25cm3 pipette: +/- 0.06 cm3
• 50cm3 burette: +/- 0.10 cm3 

A burette reading is recorded to the nearest half division. with the bottom of the meniscus on a mark or between two marks. 

Each burette reading is measured to the nearest +/-  0.05 cm3 so the reading always has two decimal places. 

 1) Use a pipette to add a measured volume of one solution to a conical flask

2) Add the other solution to a burette and record the initial reading to the nearest 0.05cm3

3) Add a few drops of indicator to the solution in the conical flask

4) Run solution in burette into the conical flask and swirl

5) Colour change indicates end point to near this point go dropwise 

6) Record the final burette reading, the titire is the volume of solution added from the burette, this is calculated by subtracting the initial from the final reading

7) Do a quick titration to find the approximate titre

8) the titration is then repeated accurately, adding the solution dropwise to the end point is approached.

9) repeat until titres are concordant- agreeing within 0.10cm3 (use these to calculate a mean titre)