Please help with chem?

Question

a 25.0-mL sample of an HCI solution is titrated w/ a 0.139M NAOH. the equivalence point is reached w/ 15.4mL of base. The concentration of HCI is.........

Answer 1

Neutralization reaction means the mole of acid = the mole of base, so once you know that you can just find out the mole of NaOH by using concentration = mole/volume

0.139M = mole/0.0154L

mole = 0.0021...mol

Now base on "mole of acid = mole of base" you can say that the mole of acid is also 0.0021...mol. So therefore to find out the concentration of the HCl, all you need to do is use the concentration = mole/volume equation again:

concentration of HCl = mole/volume

c=0.0021...mol/0.025L

c=0.0856M