Base properties of aminesAQA A-Level Chemistry: Mind map

Exam questions on Base properties of amines

1. A technician measures the pH of three aqueous solutions, each of concentration 0.100 mol dm⁻³, at 298 K. The solution of methylamine has a pH of 11.8, the solution of ammonia has a pH of 11.1 and the solution of phenylamine has a pH of 8.8.
   Write an equation for the reaction of phenylamine with water and explain why phenylamine is described as a weak base.2 marks
2. A technician has separate 0.100 mol dm⁻³ solutions of ethylamine, CH₃CH₂NH₂, and phenylamine, C₆H₅NH₂, and plans to titrate samples of each against hydrochloric acid.
   A 25.0 cm³ sample of 0.100 mol dm⁻³ ethylamine reacts with 0.125 mol dm⁻³ hydrochloric acid. Calculate the volume of acid needed to neutralise it.2 marks
3. A student measures the pH of a 0.100 mol dm⁻³ solution of ammonia at 298 K and finds it is 11.1. At this temperature the ionic product of water, Kw, is 1.00 × 10⁻¹⁴ mol² dm⁻⁶.
   Write an equation for the reaction of ammonia with water, and calculate the concentration of hydroxide ions in the solution.3 marks