GRE Subject Test: Chemistry : Titrations

Study concepts, example questions & explanations for GRE Subject Test: Chemistry

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Example Questions

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Example Question #21 : Acid Base Chemistry

A  sample of a monoprotic acid was titrated against a  solution of . If the end point was reached after adding , what is the molar mass of the weak acid?

Possible Answers:

Correct answer:

Explanation:

A pH indicator added to a solution causes a color change which is an indication that a reaction has reached the equivalence point. The equivalence point is when the number of moles of titrant equals the number of moles of analyte. The end point is an approximation of this in a titration.

At the equivalence point:

The number of moles of NaOH at equivalence point is calculated as follows:

Assuming we were trying to convert the number of grams of the monoprotic acid to moles, the equation would be set up as follows:

Let's plug the values we have into this equation and give the molar mass a value of :

Rearranging this equation to solve for the molar mass  gives:

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