mL The flask shown here contains 0.728 g of acid and a few drops of phenolphthal

Question

mL The flask shown here contains 0.728 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.170 M NaOH 15 20 25 30 35 40 45 50 What volume of base is needed to reach the end point of the titration? Number 31 mL base Click to begin 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 276 g/ mol Since molar mass has units of grams per mole, you can calculate the molar mass of a sample by dividing its mass in grams by the number of moles in that sample The number of molés of monoprotic acid in the flask is equal to the number of moles of NaOH you need to add to reach the equivalence point

Explanation / Answer

Answer

Molar mass of acid = 138.14g/mol

Explanation

The acid base reaction is

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

1mole of NaOH react with 1mole of HA

No of mole of NaOH consumed =(0.170mol/1000ml)×31ml =0.00527

No of moles of acid = 0.00527

Molar mass of acid = mass of acid/No of moles of acid

Molar mass of acid = 0.728g/0.00527mol = 138.14g/mol

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