CIE AS Chemistry (9701) exams from 2022

Revision Notes

1.7.7 Acids & Bases

Common Acids

  • An acid is a substance that neutralises a base forming a salt and water:

2HCl(aq) + CaO(s) ⇌ CaCl2(aq) + H2O(l)

acid                                salt

 

Equilibria Acid Base Reaction, downloadable AS & A Level Chemistry revision notes

Acids react with bases to form salt and water

  • Acids are also substances that release hydrogen ions when they dissolve in water:

HCl(g) → H+(aq) + Cl(aq)

 

Equilibria Acid Dissociation, downloadable AS & A Level Chemistry revision notes

Acids dissociate in water to release a hydrogen ion

Names & formulae of some common acids table

Equilibria Table 1_Common Acids, downloadable AS & A Level Chemistry revision notes

  • In organic acids (such as carboxylic acids) only some of the hydrogen atoms can form ions when the acid dissociates

Common Alkalis

  • A base is a compound that neutralises an acid forming a salt and water

2HCl(aq) + CaO(s) ⇌ CaCl2(aq) + H2O(l)

 base          salt

  • A base is a substance that accepts hydrogen ions or a compound that contains oxide or hydroxide ions
    For example:

NH3(g) + H2O(l) → NH4+(aq) + OH(aq)

base                                hydroxide ions

For example:

NaOH(s) + aq → Na+(aq) + OH(aq)

base                                hydroxide ions

  • A base that is soluble in water is called an alkali

Names & formulae of some common alkalis table

Equilibria Table 1_Common Alkalis, downloadable AS & A Level Chemistry revision notes

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