Chemistry Past Questions and Answers

(a)(i) Define allotropy.<br/>(ii) Name the allotrope of carbon used in gas masks.<br/>(iii) Mention two other elements which exhibit allotropy apart from carbon.<br/> <br/>(b) List the products of each of the following reactions:<br/>(i) Heating coal in the absence of air.<br/>(ii) Burning of candle wax in plentiful supply of air<br/> <br/>(c)(i) State the two properties of carbon (IV) oxide which make it useful in extinguishing fire.<br/>(ii) Write an equation for the reaction of carbon (IV) oxide with lime water<br/>(iii) Calculate the volume of oxygen that was in excess if 150cm\(^3\) of carbon (II) oxide was burnt in 80cm\(^3\) of oxygen according to the following equation: 2CO\(_{(g)}\) + O\(_{2(g)}\) \(\to\) 2CO\(_{2(g)}\).<br/> <br/>(d)(i) State how nitrogen can be obtained from ammonia gas.<br/>(ii) Name the gaseous fuels obtained when steam and air are passed over red hot coke.<br/>(iii) Which of the fuels in (d)(ii) has the lower heating ability? Give reason for your answer.

The atoms of four elements are represented as <sub style='font-size: smaller;'>20</sub>Q, <sub style='font-size: smaller;'>16</sub>R, <sub style='font-size: smaller;'>10</sub>S and <sub style='font-size: smaller;'>8</sub>T Which of the elements would be unreactive?

Chlorine atom forms CI by

An element Z has a combining power of 3. Which of the following formulae is correct of its compounds?

Electrovalent compounds are characterized by