I know the answer to the following question is A, but please explain your reason

Question

I know the answer to the following question is A, but please explain your reasoning. Thank you!

22. Methyl red is used as an indicator in a titration of 0.10M NaOH with 0.10M HCN. If you depend upon this indicator to complete the titration, will the titration be under-titrated or over-titrated or is it an appropriate indicator?

a. Under-titrated since the pH at the equivalence point is higher than the endpoint

b. Under-titrated since the pH at the equivalence point is lower than the endpoint

c. Over-titrated since the pH at the equivalence point is higher than the endpoint

d. Over-titrated since the pH at the equivalence point is lower than the endpoint

e. An appropriate indicator since the pH at the equivalence point is about the same as the endpoint

Explanation / Answer

option C - overtitrated since the pH at equivalence point is higher than at the end point

for titration of strong base (NaOH) and weak acid (HCN) the equivalence point is greater than 7, ph range of methyl red indicator is 4.8-6 hence it is not ab appropriate indicator for this titration.

as HCN is added gradually pH of NaOH solution decreases.....methyl red does not show colour change at equivalence point.... hence it is overtitrated

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