# Acids and Bases HL Help!!!!!!!!

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So I recently came across a question that I just can't figure out (it might be really simple but I seriously need help with this one). So here it is:

What is the concentration of OH ions (in mol dm–3) in an aqueous solution in which
[H+] = 2.0×10^–3 mol dm–3? (Kw = 1.0×10^–14 mol2 dm–6)

A. 2.0×10^–3

B. 4.0×10^–6

C. 5.0×10^–12

D. 2.0×10^–17

If you could just work through the steps to give you the answer (which by the way is C according to the markscheme) that would be great. Please help, it's killing me...

Edited by Gtemp

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Kw =[H+][OH-]. Then to solve for [OH-] it's just division.

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On 2017-9-19 at 2:44 AM, Gtemp said:

So I recently came across a question that I just can't figure out (it might be really simple but I seriously need help with this one). So here it is:

What is the concentration of OH ions (in mol dm–3) in an aqueous solution in which
[H+] = 2.0×10^–3 mol dm–3? (Kw = 1.0×10^–14 mol2 dm–6)

A. 2.0×10^–3

B. 4.0×10^–6

C. 5.0×10^–12

D. 2.0×10^–17

If you could just work through the steps to give you the answer (which by the way is C according to the markscheme) that would be great. Please help, it's killing me...

Maybe these videos will help:

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