Question

Titrations. Determine if the equivalence point (from the acid/base titration curve) will be equal to pH 7, will be lower than pH 7, or will be greater than pH 7 in the solutions below.

Strong acid/strong base

Weak acid/strong base

Strong base/weak acid

Rank the acids in order of increasing acidity:

H₂O, H₂S, H₂Se

H₃PO₄, H₂PO2, H₃PO₅

Answer 1

The equivalence point of the reaction, the point at which equivalent amounts of the reactants have reacted, will have a pH dependent on the relative strengths of the acid and base used. The pH of the equivalence point can be estimated using the following rules:

• A strong acid will react with a strong base to form a neutral (pH = 7) solution.
• A strong acid will react with a weak base to form an acidic (pH < 7) solution.
• A weak acid will react with a strong base to form a basic (pH > 7) solution.

Increasing order of acidity

H2O < H2S < H2Se, The larger the X atom, the weaker the H