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Edexcel A Level Chemistry:復習筆記1.6.3 Applying Equations

Category: A-level課程, 教材筆記, 福利干貨 Date: 2022年9月9日上午9:33

Displacement reactions

Br2?(aq) + 2KI (aq) → I2?(aq) + 2KBr (aq)

?In this reaction, the more reactive bromine?displaces?the less reactive iodide in potassium iodide
This can also be seen in the ionic equation for the reaction

Br2?(aq) + 2I-?(aq) → I2?(aq) + 2Br-?(aq)

The use of chemical equations can help identify risks and hazards in the reaction and suggest appropriate precautions where necessary

For example, the use of aqueous bromine in the above example should suggest the potential use of a fume cupboard and nitrile gloves because:

Bromine liquid is?toxic,?corrosive?and?harmful to the environment
Bromine water with a concentration of 0.2 mol dm3?is corrosive
With a concentration of between 0.06 mol dm3?and 0.2 mol dm3, bromine water is an?irritant
Only below concentrations of 0.06 mol dm3?is bromine water considered a?low hazard

Neutralisation reactions

These can be identified by the presence of reactant acids and bases as well as the formation of a?neutral salt solution?and water (and sometimes other compounds such as carbon dioxide)

HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)

Na2CO3?(aq) + 2HNO3?(aq) → 2NaNO3?(aq) +?H2O (l) + CO2?(g)

?The ionic equations can more clearly demonstrate the neutralisation of an acid and a base:

H+?(aq) + OH-?(aq) → H2O (l)

2H+?(aq) + CO32-?(aq) → H2O (l) + CO2?(g)

For neutralisation reactions, the main hazards are linked to:

The concentration of the acid
The type of acid
- This could mean?strong,? e.g. HCl, or?weak, e.g. CH3COOH
- This could also mean?monoprotic, e.g. HNO3,?diprotic,?e.g. H2SO4, or?triprotic, e.g. H3PO4
The concentration of the base
The strength of the base
The physical state of the base, e.g. NaOH (s) is arguably considered more corrosive than a high concentration solution of NaOH (aq)

Precipitation reactions