Question

3) 0.3382 g of an unknown diprotic acid, when dissolved in water, required 32.34 mL of 0.1046 M KOH to reach the endpoint. Calculate the molar mass of the unknown acid.

Also, for this problem I keept getting 99 close to 100 g/mol, but the answer has to be 200 g/mol, so can someone plz explain how you get 200g/mol?

Answer 1

H2A + 2KOH ==> H2A + 2H2O
mol KOH = 0.1046*0.03234 = 0.0033876
mol H2A = 1/2 that or 0.0016914
mol = g/molar mass or
molar mass = g/mol = 0.3382/0.0016914 =199.95 which I would round to 200.0 to 4 s.f.

Answer 2

Thank you for your help and time!