Energy conversion in a neutralisation reaction

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Energy conversion in a neutralisation reaction

Aim

We are trying to find out what factors affect the energy conversion in a neutralisation reaction.

Variables

The variables that can be changed are

Concentration of acid

Type of Acid

Concentration of alkali

We choose type of acid

Prediction

I predict that if the acid is stronger (has a lower pH) than more heat will be given out in the endothermic reaction.

Theory

Strong and Weak Acids- Acid is an H+donor and a consequence of this is that, in aqueous solutions, acid donates H+ to water molecules to produce oxonium ions H3O+. The presence of oxonium ions gives rise to the familiar acidic properties of all aqueous solutions of acids.

Acids vary in strength. Different acids donate H+ to differing extents. Strong acids have a strong tendency to donate H+: the donation of H+ is essentially complete. The reaction with water can be regarded as going to completion and can be described by the following equation, where HA represents the strong acid. (We can assume no unreacted HA remains in the solution)

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HA(aq) + H20 (l) H30+(aq) + A-(aq)

We can simplify this to

HA(aq) H+(aq) + A-(aq)

By leaving out the water, which is present in excess.

In weak acids the tendency to donate H+ is weaker and the reaction with water is incomplete. Some H+ (aq) ions are formed but there is still some unreacted acid in solution. If we represent the weak acid as HA, its reaction with water can be represented as

HA(aq) Á H+(aq) + A-(aq)

Method

We choose to change the type of acid and keep the alkali the same. We choose the alkali to be sodium hydroxide after some preliminary work. The five different types ...

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