K.C.S.E Chemistry Q & A - MODEL 1998.PP2.QN.7

27/10/2020

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KCSE Chemistry 1998 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 table below gives the solubilities of hydrated copper (II) sulphate in mol dm³ at different temperatures

(i) On the grid provided, plot a graph of solubility of copper (II) sulphate (vertical axis) against temperature.

(ii) From the graph, determine the mass of copper (II) sulphate deposited when solution is cooled from 70⁰C to 40⁰C.

(Molar mass of hydrated copper (II) sulphate = 250g)

(b) In an experiment to determine the solubility of sodium chloride, 5.0cm³ of a saturate solution of sodium chloride weighing 5.35g were placed volumetric and diluted to a total volume of 250cm³.

25.0cm³ of the dilute solution chloride completely reacted with 24cm³ of 0.1M silver nitrate solution.

AgNO₃(aq) + NaCI(aq) → AgCl(s) + NaNO₃(aq)

Calculate:

(i) Moles of silver nitrate in 24cm³ of solution

(ii) Moles of sodium chloride in 25.0cm³ of sodium

(iii) Moles of sodium chloride in 250cm³ of solution

(iv) Mass of sodium chloride in 5.0cm³ of saturated sodium chloride Solution (Na = 23.0, CI = 35.5)

(v) Mass of water in 5.0cm³ of saturated solution of sodium chloride

(vi) The solubility of sodium chloride in g/100 water

ANSWERS