I'm working on an experiment in school and I need to create 200 mL of 2 mol/L boric acid. According to a formula I found on wikipedia, boric acid can be created with a reaction with hydrochloric acid.
$$\ce{Na2B4O7·10H2O + 2 HCl -> 4 H3BO3 + 2 NaCl + 5 H2O}$$
So to calculate the amount of moles of boric acid needed, I multiplied the volume with the concentration to get 0.4 mol. After using the molar ratios in the equation, the molar mass of borax decahydrate and the concentration of HCl, I calculated that I would need 38.14 g of borax and 33.56 mL of 5.96 mol/L HCl in order for a complete reaction.
After mixing these together, I ended up with about 40 mL of a really thick solution, which is not the intended 200 mL. What did I do wrong and how do I actually create boric acid of this volume and concentration? Am I missing steps in between?