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1994 WAEC Chemistry Theory (a)(i) Draw a labelled diagram for the laboratory preparation of a dry sample of chlorine...

Chemistry
WAEC 1994

(a)(i) Draw a labelled diagram for the laboratory preparation of a dry sample of chlorine

(ii) Give one chemical test for chlorine.

 

(b) Write equations to represent the reaction of chlorine gas with: (i) iron (II) chloride solution;

(ii) potassium iodide solution;

(iii) hot concentrated sodium hydroxide solution.

 

(c) State what is observed on:

(i) bubbling hydrogen chloride gas into an solution of lead (II) trioxonitrate (V);

(ii) heating the mixture from (c)(i) above to boiling and aging it to cool.

(d) A solution of bismuth chloride was prepared by adding the oxychloride which is a white powder to concentrated hydrochloric acid. The following equilibrium was set up: BiOCI\(_{(s)}\) + 2HCI\(_{(aq)}\) \(\rightleftharpoons\) BiCl\(_{3(aq)}\) + H\(_2\)O\(_{(q)}\). State what would be observed if some water is added to the system. Explain your answer

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Explanation

(a)(i) Diagram for the laboratory preparation of a dry sample of chlorine.

 

Reactants are conc. HCI and MnO\(_2\), drying agent is conc. H\(_2\)SO\(_4\) removal of impurities is brine or KHCO\(_3\)

(i) When moist starch iodide paper is applied, the colour will change from white to blue black indicating the presence of chlorine

 

(b)(i) CI\(_2\) + 2FeCl\(_2\) \(\to\) 2FeCl\(_3\)

(ii) Cl\(_2\) + 2Kl \(\to\) 2Kcl + l\(_2\)

(iii) 3Cl\(_2\) + 6NaOH -> NaCIO\(_3\) + 5NaCI + 3H\(_2\)O

 

(c)(i) White precipitate is formed.

(ii) The precipitate disappears on heating and re-appears on cooling.

 

(d)(i) A white precipitate or suspension would form. The solution turn out to be milky. The reason is that the addition of water would drive the equilibrium to the left with the result that BiCI\(_3\) and H\(_2\)O would react to produce more BiOCI which is insoluble.
 


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