If 5.25 mL of an unknown HCl sample was titrated with 25.3 mL of a 0.00100 M solution of NaOH to its equivalence point, what is the initial concentration of the acid?

A. 4.64 × 10^-3 M
B. 4.82 × 10^-3 M
C. 8.28 × 10^-4 M
D. 2.08 × 10^-2 M

Question

If 5.25 mL of an unknown HCl sample was titrated with 25.3 mL of a 0.00100 M solution of NaOH to its equivalence point, what is the initial concentration of the acid?

 		A.	4.64 × 10^-3 M
 		B.	4.82 × 10^-3 M
 		C.	8.28 × 10^-4 M
 		D.	2.08 × 10^-2 M

vera_ewing · Answer

@JoannaBlackwelder I think it's A or B.

joannablackwelder · Answer

What calcs did you use?

vera_ewing · Answer

I couldn't figure out which ones to use, so I asked for help and someone said either A or B. I'm not sure what he did.

joannablackwelder · Answer

Ok, can you write out the acid-base reaction?

vera_ewing · Answer

Yeah I have it written down right now.

joannablackwelder · Answer

Ok, what did you get the molar ratios of the acid and base to be?

vera_ewing · Answer

Oh wait it's B! Haha sorry :) thanks!

joannablackwelder · Answer

Yep, good job. :-)

cuanchi · Answer

I dont think it is B I got a different value @vera_ewing

vera_ewing · Answer

It's B. I got it right :)

cuanchi · Answer

How come, I got D, how did you do?

joannablackwelder · Answer

Find the moles of the base, and since the reaction is equimolar in the acid and base, the acid needs the same number of moles. @Cuanchi

cuanchi · Answer

I was using the formula V1M1=V2M2 and I got D its something wrong if I use the formula @vera_ewing?

joannablackwelder · Answer

That is the same formula I used....not sure why we get different answers.