K.C.S.E Chemistry Q & A - MODEL 2007.PP2.QN.5

14/10/2020

KCSE Chemistry 2007 Topical Questions and Answers

All Questions Featuring Chemistry Form 1, Form 2, Form 3, Form 4, Paper 1, Paper 2 and Paper 3

(a) The diagram below represents part of the structure of a sodium chloride crystal.
The position of one of the sodium ions in the crystal is shown as
(i) On the diagram, mark the position of the other three sodium ions
(ii) The melting and boiling points of sodium chloride are 801°C and 1413°C respectively.
Explain why sodium chloride does not conduct electricity at 25°C, but does so at temperatures between 801° C and 1413°C
(b) Give a reason why ammonia gas is highly soluble in water
(c) The structure of an ammonia ion is shown below:

Name the type of bond represented in the diagram by N → H
(d) Carbon exists in different crystalline forms. Some of these forms were recently discovered in soot and are called fullerenes
(i) What name is given to different crystalline forms of the same element?
(ii) Fullerenes dissolve in methylbenzene while the other forms of carbon do not.
Given that soot is a mixture of fullerenes and other solid forms of carbon, describe how crystals of fullerenes can be obtained from soot.
(iii) The relative molecular mass of one of the fullerenes is 720. What is the molecular formula of this fullerene? (C=12.0)

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