# Chemistry

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My final exam is coming up so I am doing study guides to help me practice. I would really appreciate any help that is given.

1. The hydronium ion concentration for a solution is determined to be
4.5 x 10^-7 M. What is the concentration of the hydroxide ion?

2. When a 5.00 mL sample of vinegar is titrated, 44.5 mL of 0.100 M NaOH solution is required to reach the end point. What is the concentration of vinegar in moles per liter of solution?

I'm not really sure what numbers to put where so if you could please walk me through how to do this so I can use it as a how-to for other problems like it on the study guide I would greatly appreciate it.

• Chemistry - ,

1.
(H^+)(OH^-) = Kw = 1E-14
Substitute for H^+ and solve for OH^-

2.
vinegar is acetic acid, HAc.
HAc + NaOH ==> NaAc + H2O
mols NaOH = M x L = ?
mols HAc = mols NaOH (Look at the coefficients in the balanced equation.) That's mols in 5.00 mL of the solution.
Then M HAc = mols HAc/L soln.
(you know L soln = 0.005L)

• Chemistry - ,

Thank you. That helps.