mL Res The flask shown here contains 0.457 g of acid and a few drops of phenolph

Question

mL Res The flask shown here contains 0.457 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.290 M NaOH. 10 2015 30 20 What volume of base is needed to reach the end point of the titration? 25 Number R2AM 0.002465mL base 40 45 Assuming the acid is monoprotic, what is its molar mass? Add base to the solution until it just turns pink. You may need to reset the titration if you go past the end point. Number 185.40 g/ mol You may not have reached the end point of the titration yet, or you may be reading the volume in the buret incorrectly. Be sure to read the liquid level at the botiom of the meniscus. Once you see pink that fades away in the flask continue adding base drop by drop until the pink color persists in the

Explanation / Answer

Frim burette reading we get:

Volume of base : 18 ml

18 ml of 0.290 M NaOH is required to neutrslise the acid.

18 ml of 0.290 M NaOH solution contains 18×0.290/1000 mole = 0.00522 mole NaOH

0.00522 mole NaOH neutralises 0.00522 mole of the monoprotic acid. If x be the molar mass of the acid;

0.457/ x = 0.00522

Or; x = 87.6

The molar mass of the acid is: 87.6 g/ mole

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