Equilibrium and indicator equation

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Increasing alkali, such as NaOH, introduces OH- ions that react with H+ ions, reducing their concentration. This shift in H+ concentration leads to a decrease in HIn, causing the equilibrium to shift to the right, favoring the formation of more H+ and In-. The coursebook's assertion that the equilibrium moves to the right aligns with Le Chatelier's principle, which states that a system will adjust to counteract changes. The confusion arises from interpreting equilibrium in terms of weights rather than chemical concentrations. Understanding the dynamics of the reaction and the role of alkali is crucial for grasping these concepts in chemistry.
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The equation for indicator is:
HIn ⇌H+ + In-
Which reaction (forward or reverse) will be preferred when I increase the Alkali.
According to me, The reverse reaction should be preferred as the reaction will try to minimize the effect of the change. Hence In- (i.e the conjugate base) will be increased as it will react with H+ to form HIn.
But the coursebook says that the position of the equilibrium will move to the right. Kindly explain why is that so?
 

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How would the reverse reaction minimise the effect of the change?
How is [In-] increased by reacting with H+?
 
Not enough information to answer. Alkali what? Alkali salt? Alkali base?
 
haha0p1 said:
The equation for indicator is:
HIn ⇌H+ + In-
Which reaction (forward or reverse) will be preferred when I increase the Alkali.
According to me, The reverse reaction should be preferred as the reaction will try to minimize the effect of the change. Hence In- (i.e the conjugate base) will be increased as it will react with H+ to form HIn.
But the coursebook says that the position of the equilibrium will move to the right. Kindly explain why is that so?
The question should be in the homework section. I think it is a good question, deserving some attention by chemistry teachers. I think when I first met this subject at school I felt confused, the reason being what I saw as ambiguous expressions like "the equilibrium will move to the right" I was thinking of equilibrium as weights on a lever… but never mind.

Help yourself by writing out the equation for the equilibrium constant relating [HIn] to the dissociation products molarities [H+] and [In-]. "Adding alkali" means adding something like NaOH, I.e. essentially adding OH- to the solution, which will react with H+ there, and directly or indirectly with HIn (it matters not which) to do - what? So think again through what will happen – you have got it wrong.

I think it is better to work out your own way of thinking and talking about these things (which you are likely to meet again again) rather than someone else's way of expressing it.
 
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