The action of heat on the blue crystalline solid A, gives a reddish brown gas B, a gas which re-lights a glowing splint and leaves a black residue. When gas C, which has a rotten egg smell, is passed through a solution of A, a black ppt. is formed.
(a) Identify A, B and C
(b) Write an equation for the action of heat on A.
(c) Write equation between solution of A and gas C. [5 MARKS]

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Solution

a) 3 Marks
b) 1 Mark
c) 1 Mark

(a) A - Copper nitrate, $C u (N O_{3})_{2}$ - a blue crystalline solid
B - Nitrogen dioxide $(N O_{2})$ - a gas which relights a glowing splint
C - Hydrogen sulphide gas $(H_{2} S)$ - a gas with a smell of rotten eggs
(b) $2 C u (N O_{3})_{2} B l u e, c r y s t a l l i n e s o l i d Δ \to 2 C u O B l a c k r e s i d u e + 4 N O_{2} R e d d i s h b r o w n g a s$
(c) $C u (N O_{3})_{2} + H_{2} S \to C B S (d) B l a c k p p t . + 2 H N O_{3}$

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