Answer :
The litmus paper is useful for detecting the endpoint of the reaction between bromotriphenylmethane and ethanol because of the production of HCl that can interact with litmus.
What is litmus paper?
The term litmus paper refers to an organic paper that can be used to detect the presence of an acid or a base. It happens because the color of the dye that was used to make the paper is able to change in response to the hydrogen ion concentration of the solution.
This implies that the litmus paper would have a different color in an acid and a basic medium. In this case, we are considering the reaction between bromotriphenylmethane and ethanol which produces hydrochloric acid as a side product.
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