The flask shown here contains 0.502 g of acid and a few drops mL of phenolphthal

Question

The flask shown here contains 0.502 g of acid and a few drops mL of phenolphthalein indicator dissolved in water. The buret contains 0.270 M NaOH. What volume of base is needed to reach the end point of the titration? 10 15 mL Number mL base 5 50 What is the molar mass of the acid (assuming it is diprotic and that the end point corresponds to the second equivalence point)? Add base to the solution until it just turns pink. You may need to reset the titration if you go past the end point. g/ mol Previous Give Up & View Solution (2) Check Answer e) Next t1 Exit int

Explanation / Answer

Concentration of acid = (0.502/Molar mass of acid)/0.050 (it appears that the volume of acidic solution is 50mL) = 10.04/molar mass M

Since the acid is diprotic, Vollume of NaOH = ((2*10.04)/M.Mass-acid)/0.27 = 74.37/M.mass mL

If the concentration of acid is known, the molar mass of acid can calculated

and once molar mass of the acid is determined, then volume of base can be found out.

Because it is a titration of an unknown acid against NaOH of known concentration, the volume of NaOH solution added can be observed/measured from the buret. From this, molar mass of the acid can be calculated using this equation: Molar mass of acid = 74.37/VNaOH g/mol

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