Question 17 of 31 Sapling Learning The flask shown here contains 0.606 g of acid

Question

Question 17 of 31 Sapling Learning The flask shown here contains 0.606 g of acid and a few drops of hthalein indicator dissolved in water. The buret contains 0.220 M NaOH What volume of base is needed to reach the end point of the titration? Number mL base 25 What is the molar mass of the acid (assuming it is diprotic and that the end point corresponds to the second equivalence point)? se to the solution until it just turns pink. You may need to reset the titration if you go past the end point Number g/ mol

Explanation / Answer

volume of NaOH = 19ml
molarity of NaOH = 0.22M
H2A is diprotic acid
no of moles of NaOH = molarity * volume in L
                     = 0.22*0.019   = 0.00418moles
H2A + 2NaOH -------------> Na2A + 2H2O
2 moloes of NaOH react with 1 moles of H2A
0.00418 moles of NaOH react with = 1*0.00418/2   = 0.00209 moles of H2A
molar mass of H2A = mass of H2A/no of moles of H2A
                   = 0.606/0.00209   = 289.95g/mole

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