Acid Bath Murder

http://www.discoverychannel.co.uk/web/crime-museum-uk/episode-guide/acid-bath-murder/

Sulphuric acid:- Making detergents- Making fertilisers- In car batteries

Ethanoic acid:- (In vinegar) to preserve food- In making adhesives such as glue

Hydrochloric acid:- In leather processing- For cleaning metals

An acid is a substance that produces hydrogen ions,

H+ (aq) in water.

Acids only show the properties of acids when they are dissolved in water.

Acids only show the properties of acids when they are dissolved in water.

Exists as molecules when dissolved in organic solvents like alcohol

HCl dissociates into H+

and Cl- when dissolved in water

Acids dissociate in water to produce hydrogen ions which are responsible for the acidic properties.

How about sulfuric acid and nitric acid?

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

Reaction with metals2H+ (aq) + Mg (s) H2 (g) + Mg2+ (aq)

The H+ ions (produced by HCl) allows acids to react with the metal, magnesium.

Similarly, the H+ ions from the acid are responsible for the other reactions with carbonates, hydrodencarbonates, hydroxides and oxides.

from HCl (aq)

An ionic equation is an equation involving ions in aqueous solution; only those ions formed or changed during the

reaction are included.

The maximum number of hydrogen ions produced by a molecule of an acid is called the basicity of the acid.

E.g. Hydrochloric acid is monobasic. Sulfuric acid is dibasic.

Can you think of a tribasic acid?

Can you tell the difference?

A strong acid is one that completely ionises in water.

All acid molecules become ions in the water.

Examples of strong acid: HCl (aq) HNO3 (aq) H2SO4 (aq)

E.g. HCl (aq) H+ (aq) + Cl- (aq)

A weak acid is one that partially ionises in water.

Most acid molecules remain unchanged in the water (99%)

Examples of weak acid: Ethanoic acid CH3COOH Citric acid C6H8O7

Phosphoric acid H3PO4

Eg. CH3COOH (aq) CH3COO- (aq) + H+ (aq)

Would you expect the reactivity to be different?

Yes, strong acids react more vigorously than weak acids.

‘Strong’ does not mean ‘concentrated’. ‘Weak’ does not mean ‘dilute’.

Strength refers to the extent to which the acid molecule dissociates when dissolved in water.

Concentration refers to the amount of solute in the solution.

The term concentration tells us how much of a substance is dissolved in 1 dm3 of a solution.

It can be changed, either by adding more solvent or solute.

Adding solvent to make it dilute

Adding solute to make it

concentrated

Strong acid

Weak acid

Concentrated, strong acid

Dilute, strong acid

Strength VS Concentration

The strength of an acid can be shown on a pH scale.

In ionic equations: Formulae of ions that change (react) are

included; ions that do not change are omitted.

Formulae of solid, liquid, gases are written in full