Ch 12 #27

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Ch 12 #27

Postby donnanguyen1d » Mon Dec 04, 2017 9:31 pm

How come for part B of the question the solution would be (200 mL x .025M HCL)/ (250ml)
why do you multiple the M and the volume and then divide by the other volume? What's the conceptual idea behind this

Michelle Dong 1F
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Re: Ch 12 #27

Postby Michelle Dong 1F » Mon Dec 04, 2017 10:53 pm

I believe it's like calculating M2 using the M1V1=M2V2 equation. M1=0.025 and V1=0.2 L. M2=? and V2=0.25 L. In order to find M2, you divide 0.025*0.2 by 0.25, and that gives you 0.02 M. Since HCl dissociates all the way and creates H3O+ ions, we can assume that the concentration of H3O+ is also 0.02. When you plug it into the pH equation, you get 1.7.

Janine Chan 2K
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Re: Ch 12 #27

Postby Janine Chan 2K » Tue Dec 05, 2017 12:40 am

We multiply 200 ml by .025 M to find the number of moles that were actually made. Then divide by 250 ml to get the molarity of the actual solution.

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