For the following acid pairs determine which solvent could b

For the following acid pairs, determine which solvent could be used to be used to discriminate between the acidities: PH3 (pKa 27) vs GaH4 (pKa 25) Ph(=O+H) OH(pKa=-7.8) vs Ph(=O+H)CH3(pKa=-6.2) Explain why water could not be used to discriminate between the pKa values for either of these acids.

Solution

The pH range allowed by a particular solvent is called the acid-base discrimination window

a) DMSO(Dimethylsufoxide) {acid-base discrimination window of pH 0 to 30}

b) Methanoic acid {acid-base discrimination window of pH -2 to -10}

c)Water could not be used to discriminte between the pKa for either of these acids as its acid-base discrimination window is of pH 0 to 14 .Any acid that is stronger than H₃O⁺ reacts with H₂O to form H₃O⁺. Therefore, no acid stronger than H₃O⁺ exists in H₂O.