3. Another student titrated a0.4721 g sample of unknown monoprotic acid with 0.1

Question

3. Another student titrated a0.4721 g sample of unknown monoprotic acid with 0.10801M sodium hydroxide per theproc ll Using the firs der ivative curve, the student found the equvalence point volumeto be 28.77 mL sodium hydrokide a. Calculate the number of moles of sodium hydraxide used in the titration NG1 b. How many equivalents of unknown acid were ttrated? c. Determine the equiv alent mass of the unknown acid 4. Of the buffers pH 4, 7 and 10, which two would you use to ces tbrare a pht probe for a wesx bace- grong acid titration? Explain your answer

Explanation / Answer

3) mass of unknown acid = 0.4721 g

Let the equivalent mass of acid = E

molarity of base = 0.10801 M

volume of base used = 28.77mL

part A)

number of moles of NaOh used = molarity x volume (L)

= 0.10801 x 28.77x10-3

= 3.1075 x10-3 moles

part B) In an acid base titration

The equivalents of acid used = the equivalents of NaoH used

= 3.1075 x10-3 equivalents

part C ) The equivalent mass of acid is calculated as

number of equivalents = mass/ equivalent mass

= 0.4271/E

From the tiration

number of equivalent of acid = equivalents of NaOH

Thus 0.4271/E = 3.1075x10-3

Thus equivalent mass of acid E = 137.44 g/eq

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