AP Chemistry Question- pH/Molarity?

Question

How do you answer or begin to work the following problem:

3.2 mL of NaOH neutralizes 4.55 mL of 0.0075 M HCl. What was the pH of the acid solution before neutralization.

Thanks!

Answer 1

pH = -log [H+]
where [H+] is the concentration of the H+ ion in the solution.

You are told that the initial concentration of HCl in the solution was .0075 Molar.
For every 1 mole of HCl in solution, there is also 1 mole of H+ ion solution since HCl is a strong electrolyte and will completely break up into H+ and Cl- ions.

So [HCl] = [H+] = 0.0075 M

You can now calculate the pH as,
pH = -log [0.0075]
pH = 2.12

Answer 2

gimmie points. =p

ok, one molecule of NaOH will yield one OH- ion while one HCl molecule will yield one H+ ion. thus, they react in a 1 to 1 ratio. H+ and OH- form H2O -- water.

i guess none of that really matters though because it simply wants you to find the pH of the acid solution, and it gives you everything you need to just plug into an equation.

M, or molarity, means mols / liter.

a formula for pH is:
pH = -log([H+])

[H+] means H+ concentration, or molarity.
[H+] = [HCl] because there is one H+ in every HCl.

pH = -log(0.0075) = 2.12493874, and minding significant digits,
pH of the HCl solution is: 2.1

[e-mail] <-- if you need more help in your studies.

pH = -log([H+])

Answer 3

most of the information given seems unimportant, except the original molarity of HCl. because HCl is a strong acid and dissociates completely, there would be 0.0075M H+ in the original solution. neg-log of that is the pH, which is 2.12

Answer 4

i took AP Chem and i thought i was pretty good at chem. but OMG its hard. really hard. take drawing if that was you really want ! follow your heart lol if your worried about getting into a pre-med program take BIO i guess...but just remember by the time u go through college (if ur still interested in med-a lot can happen in college) the med schools u apply for wont really be interested in what class you took in high school. and many colleges require u to score at least a 4 on the AP test to accept it as any college credit

Answer 5

The HCl solution is 0.0075 mole HCl/liter

pH = - log [conc HCl] - log [ 0.0075] = 2.12

Answer 6

difficult to answer since both chemicals are still under fusion, you might wanna ask this question to a Chemistry Teacher

Answer 7

Try looking it up in your textbook.