Question 3 of 4 Sapling Learning mL, 10 15 20 30 45 50 Hint Map A Reset The flas

Question

Question 3 of 4 Sapling Learning mL, 10 15 20 30 45 50 Hint Map A Reset The flask shown here contains 0.141 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 110 M NaOH. What volume of base is needed to 10 reach the end point of the titration? Number 15 mL base Assuming the acid is monoprotic, what is its molar mass? Number Add base to the solution until it just turns pink. You may need to reset the g mol titration if you go past the end point AO Previous Give Up & View Solution Check Answer Next SExit

Explanation / Answer

The acid is monoprotic

HA + NaOH ------> NaA + H2O

From the stoichiometry of this reaction , we can understand 1mole of Acid ( HA) react with 1 mole of NaOH

Molarity of NaOH = 0.110M

0.110M =0.110 mole in 1000ml

Volume of NaOH consumed ( from the picture - lower meniscus) = 10.3ml

No of mole of NaOH = (0.110mole/1000ml)×10.3ml = 0.001133 mole

0.001133 mole of NaOH react with 0.001133mole of Acid

Therefore, No of mole of Acid = 0.001133

Mass of Acid = 0.141g

No of mol = Mass / Molar Mass

Molar mass = Mass / No of mole

= 0.141g/0.001133

= 124.45g/mole

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