Sasha Shasha
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Write an equation with state symbols for first ionisation of h2s when it dissolves in water.
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eeiiiiio
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H2S (aq) + H2O (aq) <-> HS- (aq) + H3O+ (aq)
(acid 1) . . (base 2) . . . . (base 1) . . (acid 2)


Hydrogen sulphide acts as a weak acid in water, so donates a proton to the water molecule (which then becomes an acid - the hydronium ion)

It is reversible because it is an acid-base reaction and most are reversible.
(and theoretically all reactions are?)
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Sasha Shasha
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Why in marking scheme they just state a single arrow ? Does strong acids have reversible reaction too ? Equilibrium sign should be written or not for the chemical equation of strong acid
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(Original post by Sasha Shasha)
Why in marking scheme they just state a single arrow ? Does strong acids have reversible reaction too ? Equilibrium sign should be written or not for the chemical equation of strong acid
Strong acids have the single arrow because they don't generally react backwards, so are classed as 'irreversible' whereas weak acids may have the double arrow because they do not react 'fully'.

The markscheme probably had a single arrow because the question asked specifically for the ionisation of H2S. I would say it's correct to put either in that case. I don't think it's something that would be penalised, but I may be wrong.
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