2018 - JAMB Chemistry Past Questions and Answers - page 8

The law of multiple proportion states that when element A and B combine to form more than one chemical compound then the various masses of sample A react with a fixed mass of sample B are in a simple multiple ratio.

p\(^{OH}\) = -Log [OH\(^-\)]

  [OH\(^-\) ] = 2.0 X 10\(^{-11}\)moldm\(^{-3}\)

  p\(^{OH}\) = -Log [2.0 X 10\(^{-11}\)]

  p\(^{OH}\) = 10.70

Ammonia gas can be removed from a dessicator by adding a conc. H2SO4 so as to neutralize it since ammonia gas is basic.

Aluminium doesn’t react with either dilute or concentrated trioxonitrate (V) acid because an insoluble oxide is formed on its surface which renders it passive. It will depend on the concentration of the nitric acid used…. Although aluminium reacts with dilute nitric acid to produce aluminium nitrate and hydrogen gas, concentrated (>60%) nitric acid is such a powerful oxidising agent that it instantly causes a thin layer of aluminium oxide to coat the surface of the aluminium

Tap water contains less Ca\(^{2+}\) and Mg\(^{2+}\)

The conductivity of a solution depends on the number of charge carriers (the concentrations of the ions), the mobility of the charge carriers and their charge. Theoretically, conductivity should increase in direct proportion to concentration.