WAEC Chemistry 2014 Paper

Concept:Thermal decomposition of copper(II) nitrate produces copper(II) oxide, nitrogen dioxide, and oxygen.Explanation:When solid copper(II) nitrate is heated, it breaks down into a black solid residue and two gases.The balanced equation for the decomposition is:$$2\mathrm{Cu(NO_3)_2(s)} \xrightarrow{\Delta} 2\mathrm{CuO(s)} + 4\mathrm{NO_2(g)} + \mathrm{O_2(g)}$$From the equation, the gas products are nitrogen dioxide ($\mathrm{NO_2}$) and oxygen ($\mathrm{O_2}$).$\mathrm{NO_2}$ is a brown gas, while $\mathrm{O_2}$ is a colourless gas that supports combustion.No other gaseous products are formed in this reaction.Answer:D. $\mathrm{O_2}$ and $\mathrm{NO_2}$