So I did a titration lab at school with NaOH and HCl. i have to find:

Question

- volume used, NaOH
- Moles of NaOH
- Moles of HCl
-Volume used unknown HCl
- Molarity of HCl solution

My concentration of NaOH stock solution was 0.100 mol/lL

Final buret reading, NaOH: 14.20 ml
Initial buret reading, NaOH: 50 ml

What I did :

Volume used NaOH: 35.8 mL (I subtracted 50 mL from 14.20 mL.. Am I doing this right??)

Moles of NaOH: 3.58 mol
Because n= C xV
n= (0.100 mol/L)(35.8 mL)

HCl (aq) + NaOH (aq) = H2O (l) + NaCl (aq)
That's what I think the chemical equation would be. So it's already balanced. I would do:

Moles HCL over moles of NaOH= 1 mole over 1 mole...
So wouldn't HCl have the same number of moles??

How could I find the volume used for unknown HCl if I don't know the concentration or volume???

I really appreciate the help, it means a lot

Answer 1

Volume used NaOH: 35.8 mL (I subtracted 50 mL from 14.20 mL.. Am I doing this right??)
You did it right but said it wrong. Volume is 50-14.20 = 35.8 mL NaOH BUT you subtracted 14.20 from 50 not the other way around.

Moles of NaOH: 3.58 mol
Because n= C xV
n= (0.100 mol/L)(35.8 mL)
Exactly right.

HCl (aq) + NaOH (aq) = H2O (l) + NaCl (aq)
That's what I think the chemical equation would be. So it's already balanced. I would do:

Moles HCL over moles of NaOH= 1 mole over 1 mole...
So wouldn't HCl have the same number of moles??
Yes, mols HCl = mols NaOH = 3.58

How could I find the volume used for unknown HCl if I don't know the concentration or volume???
You should have the volume of the HCl if this were a titration in the lab. You probably started with a known quantity of HCl, measured either with a buret or some other device.
Then since M HCl = mols HC/L HCl. You know mols HCl from above and L HCl you started with, solve for M HCl. Look in your lab notes or think back. You HAD to have some HCl in the titration flask when you started titrating with the NaOH. The only way it can get there is for you to have added it OR for your instructor to have handed you a flask containing the HCl. If you added it you know how much you added. If the instructor gave it to you s/he must tell you how much is there.