Extraction Of Metals Result Question 75
75. Write balanced chemical equation for developing a black and white photographic film. Also give reason, why the solution of sodium thiosulphate on acidification turns milky white and give balance equation of this reaction.
$(2005,2 M)$
Show Answer
Solution:
- (a)
$2 \mathrm{AgBr}+\underset{\text { Hydroquinone (developer) }}{\mathrm{C}_4 \mathrm{H}_4(\mathrm{OH})_2} \longrightarrow 2 \mathrm{Ag}+2 \mathrm{HBr}+\underset{\text { Quinone }}{\mathrm{C}_6 \mathrm{H}_4 \mathrm{O}_2} $
$\mathrm{AgBr}+2 \mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3 \longrightarrow \mathrm{Na}_3\left[\mathrm{Ag}\left(\mathrm{S}_2 \mathrm{O}_3\right)_2\right]+\mathrm{NaBr}$
(b) $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3+2 \mathrm{H}^{+} \longrightarrow 2 \mathrm{Na}^{+}+\mathrm{H}_2 \mathrm{SO}_3+ \underset{\text{Colloidal sulphur}}{\mathrm{S} \downarrow}$
BETA
