Chem HELP Molarity

Question

Oxalic acid dihydrate is a solid, diprotic acid that can be used in the laboratory as a primary standard. Its formula is H2C2O4•2H2O.

A student dissolves 0.896 grams of H2C2O4•2H2O in water and titrates the resulting solution with a solution of barium hydroxide of unknown concentration. If 38.2 mL of the barium hydroxide solution are required to neutralize the acid, what is the molarity of the barium hydroxide solution ?

Answer 1

Lets start by writing a balanced chemical equation for the titration/ neutralization process:

 

                      H₂C₂O₄.2H₂O + Ba(OH)₂ =  BaC₂O₄ + 4H₂O

 

1 mole H₂C₂O₄.2H₂O = 1 mole Ba(OH)2 = 126g H₂C₂O₄.2H₂O 

 

Equality of mass and volume:

0.896g H2C2O4.2H2O = 0.0382 L Ba(OH)2

 

Our goal = mol Ba(OH)₂/L Ba(OH)₂ = Molarity of Ba(OH)₂

 

Now lets set up the given values and calculate the unknown:

 

     1mol Ba(OH)2                   0.896 g H2C2O4.2H2O
-------------------------------  x  ---------------------------- =  0.186 mol/L Ba(OH)2
126 g H2C2O4.2H2O                0.0382 L Ba(OH)2

The molarity of barium hydroxide is 0.186 M.