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    Consider the following simplified equilibrium for an indicator, HIn.

    HIn(aq) ~~~~ H+(aq) + In–(aq)
    Yellow Purple

    Addition of a few drops of sodium carbonate solution would
    A make the colour of the equilibrium mixture turn purple and then yellow.
    B make the colour of the equilibrium mixture paler.
    C make the equilibrium mixture more yellow.
    D make the equilibrium mixture more purple.

    Correct answer is D
    Don't know why
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    (Original post by Sarwa)
    Consider the following simplified equilibrium for an indicator, HIn.

    HIn(aq) ~~~~ H+(aq) + In–(aq)
    Yellow Purple

    Addition of a few drops of sodium carbonate solution would
    A make the colour of the equilibrium mixture turn purple and then yellow.
    B make the colour of the equilibrium mixture paler.
    C make the equilibrium mixture more yellow.
    D make the equilibrium mixture more purple.

    Correct answer is D
    Don't know why
    The sodium carbonate reacts with the H+ ions in the equilibrium pulling it to the RHS and the purple colour intensifies.
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    Why doesn't sodium carbonate react with HIn?
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    (Original post by Sarwa)
    Why doesn't sodium carbonate react with HIn?
    Because HIn is molecular and cannot interact with the carbonate ion.
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    (Original post by charco)
    Because HIn is molecular and cannot interact with the carbonate ion.
    oh okay thanks
 
 
 
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