You added solid sodium hydrogen sulfate solution to NaHSO4 and thymol blue and o

Question

You added solid sodium hydrogen sulfate solution to NaHSO4 and thymol blue and observed a color change.

and explain which way the equilibrium is shifting by using La Chatelier princple.

I think this would be the right answer but im not sure "When solid sodium hydrogen sulfate is added to the well,

the equilibrium shifts to the right (product) in order to lower the concentration of the hydrogen sulfate ion.

This shift in equilibrium also causes the acid concentration to increase. The color change from a rose red to

a purple-red solution indicates the acid concentration has increased, which supports the shift in the equilibrium

to the product (right) side."

You added solid sodium hydrogen sulfate solution to NaHSO4 and thymol blue and observed a color change.

and explain which way the equilibrium is shifting by using La Chatelier princple.

I think this would be the right answer but im not sure "When solid sodium hydrogen sulfate is added to the well,

the equilibrium shifts to the right (product) in order to lower the concentration of the hydrogen sulfate ion.

This shift in equilibrium also causes the acid concentration to increase. The color change from a rose red to

a purple-red solution indicates the acid concentration has increased, which supports the shift in the equilibrium

to the product (right) side."

Explanation / Answer

The ion HSO4- is :

- a weak acid   (HSO4- + H2O < == > SO42- + H+)       (A)

- an ineffective base (because the conjugated acid H2SO4 is strong)

You may consider HSO4- as a monoprotic weak acid HA and not an amphoter at least for a pH estimation.

Thymol blue has a transition red/yellow at pH 1.2(red)…2.8(yellow).

By adding solid NaHSO4, you have more HSO4- in solution and, according to Le Chatelier principle, more H+ by dissociation.

The initial and final pH were both acidic (the solution contains a weak acid). For a clear colour change, you may assume that the initial pH was >2.8 and the final pH<1.2

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