Hello.

Question

For my chemistry of solutions class, we had a titration lab where we titrated NaOH into an HCl + H2O mix. This was a preparatory titration for the next one consisting of the hydrolysis of ethyl acetate into acetic acid with H+ ions as a catalyst (in our case the HCl).

So now, after we did 4 stock HCl titrations which are the practice ones, we're asked those 2 questions:

Mass of HCl in 5.00 mL HCl solution
Mass of 5.00 mL HCl solution (d=1.05g/mL)

Now I put the same answer in both as 5mL * 1.05 g/mL = 5.25g.
So my question is, what exactly is the difference between those 2 questions, are they asking for the same thing?

Also, further down they ask to find the Mass of H2O in 5mL HCl solution and the moles of H2O. Is this going to be calculated using the water density?

Thank you for your time.

Answer 1

So I was thinking that when we use the NaOH, because of the stoichiometry of it's reaction with HCl, would the mass used of NaOH be the same for HCl, when it reaches equilibrium, well the neutral pH? Or am I completely off

Answer 2

Those are two different questions.
mass HCl in 5.00 mL = mols HCl in 5.00 mL x molar mass HCl
mass 5.00 mL soln = 5.00 x 1.05 g/mL = ?

Because of the stoichiometry of the titration of NaOH + HCl, the MOLES are equal at the equivalence point but not the grams. 1mol HCl = 1 mol NaOH or 36.5 g HCl and 40 g NaOH. So mols are equal but not grams.

Answer 3

Amazing, thank you DrBob!