Chemical Reactions: Aqueous Solutions

Aqueous Solution

Solution in which the solvent is water

Polar Molecule

Molecule that has two oppositely-charged poles and is known as a dipole

Dissociation

Ionic compounds are released from the crystal lattice

Dissociation process

Strong attractive forces from the polar sides of the water molecules attract the positive and negative ions in the crystal

Ionisation

Covalent compounds form ions in water

Ionisation process

Originally there are no ions present, but during the dissolution process ionisation of polar molecules occurs

Which covalent molecules ionise?

acids and ammonia

Dissolution process

Process whereby a solid moves into the solvent

Which processes make up the dissolution process?

1. Dissociation 2. Ionisation 3. Dissolving covalent molecules that don't ionise (sugar, C12H22O11)

Hydration

Process whereby ions are surrounded by water molecules in an aqueous solution

What are polar molecules attracted by?

1. negative ions attract the water molecules so that the positive pole (side) is directed towards the
negative ions.
2. Positive ions attract the water molecules so that the negative pole (side) is directed towards the
positive ions.

Solution

A homogeneous mixture of two or more substances

Solute

The dissolved substance in a solution - usually
the substance present in lesser amount.

Solubility

The maximum amount of a substance (the solute) that may be dissolved in another substance (the solvent)

Solvent

The substance in a solution in which the solute is dissolved - usually the substance present in greater amount

Electrolyte

any liquid which contains free ions and can conduct
on electrical current through the movement of the ions

What does the electrical conductivity of an aqueous solution depends on?

1. concentration of the ions in solution (higher concentration of ions in the solution are better conductors of electrical current)
2. type of substance 3. Increase in temp

Non-electrolyte

When a substance does not form ions in solution, it does not conduct a current.

Precipitate

insoluble substance that is formed during a chemical reaction.

Molecular equation

The reactants and products are written as molecules NaCl(aq) + AgNOg(aq) - NaNO,(aq) + AgCI(s)

Ionic equation

A the soluble substances are written as ions. Na (aq) + Cl- (aq) + Ag (aq) + NO3- (aq) -> Na +(aq) + NO3- (aq) + AgCl (s)

Net ionic equation

Only the reactants involved in the production of the precipitation are included in the comparison
Ag+ (aq) + Cl-(aq) -> AgCl(s)

Where do Redox reactions occur?

occur in batteries, combustion of fuels and natural reactions like respiration.

What does a redox reaction consist of?

- Consist of Oxidation substances and a reduction half reaction. - These two reactions are complementary processes- take place simultaneously

What happens during a redox reaction

A transfer of electrons take place

Redox reaction

Reaction between an oxidising and reducing substance in a chemical reaction

acid base reaction

transfer of protons

gas-forming reaction

when a gas forms during a reaction