求救!hkcee問題!bleaching!

由於Cl2 同埋 SO2都係酸性氣體，所以佢地都會將MOIST blue litmus paper turn to blue. 但係由於兩隻都係有bleaching effect嘅，所以會將試紙轉白。
我兩個月前做過chlorine bleaching嘅experiment，其實由blue轉白之間，係有2~3秒見到紅色嘅，所以Cl2應該係將blue litmus paper turns to red then white。SO2, 由於佢嘅bleaching effect比較mild，所以係會有多啲時間睇到紅色。

兩種chemical嘅bleaching equation:
chlorine:
Cl2 (g) + H2O (l) → HOCl (aq) + HCl (aq)
OCl- (aq) + dye (coloured) → Cl- (aq) + [dye + O] (colourless, bleached, oxidizied)
Sulphuric dioxide:
SO2 (g) + H2O (l) → H2SO3 (aq)
SO3 2- (aq) + dye (coloured) → SO4 2- (aq) + [dye - O] (colourless, bleached, reduced)

大家都會令blue litmus paper 由blue 變成 red 再變 white

不過the bleaching process of Cl2 is much faster, so it seems the paper turned from blue to white.

總之最後都會變白啦