Mapo apling Learning mL The flask shown here contains 0.354 g of acid and a few

Question

Mapo apling Learning mL The flask shown here contains 0.354 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.120 M NaOH 5 10 15 e 20 What volume of base is needed to reach the end point of the titration? 30 35 40 Number mL base Click to begin 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 Number you go past the end point g/ mol 0 Previous Give Up & View Solution O Check Answer O Ne xt Exit

Explanation / Answer

Steps:

1) use the buret on the right to dispense the required amount of titrnat ( NaOH)

stop when solutino turns pink color

V = read the volume, recall that we msut record the lowest ( meniscus value) volume

2)

calculate

NaOH + HA <-> NaA H2O

mmol of NaOH = MV = 0.12 * Vbase

then

mmol of Ha = mmol of NaOH = 0.12 * Vbase

now...

MM = mass of HA / mmol of Ha = 0.354 / (0.12 * Vbase) = 2.95 / (Vbase in liter) = 2950 /Vbase in mL

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