Sapling Learning The flask shown here contains 0.775 g of acid and a few drops o

Question

Sapling Learning The flask shown here contains 0.775 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.150 M NaOH. What volume of base is needed to reach the end point of the titration? Number mL base What is the molar mass of the acid (assuming it is diprotic and that the end point corresponds to the second equivalence point? Number g/mol mL 20 25 300 35 40 45 Map Reset 20 25 30 Add base to the solution until it just turns pink. You may need to reset the titration if you go past the end point.

Explanation / Answer

Volume of base needed = 26.0 mL

Moles of base used = 0.150 * 27.0 / 1000 = 0.00405 mol

So, same number of moles of acid should also present to reach to equilbrium state.

So, number of moles ofacid = 0.00405 mol

moles = mass / molar mass

therefore,

molar mass = 0.775 / 0.00405 = 191.4 g/mol

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