Quiz 1 Prep: Fall 2015, Question #1 [ENDORSED]

Eva_Wetzel_3K
Posts: 8
Joined: Wed Sep 21, 2016 2:56 pm

Quiz 1 Prep: Fall 2015, Question #1

I was able to figure out the first part, but my trouble is with this question in the workbook:

"How many milliliters of the stock solution would you need to add to obtain a 250 mL 0.650 M NaOH solution?" (Given that in the previous part of the question, we prepared a 3.0*10^3 mL stock solution with 2.00 M of NaOH using 24.0 g of NaOH) (And the answer to this is 81.3 mL)

I tried using the molarity equation by plugging in .6 for # of moles, and .650 for M. This didn't seem to be the right way to do it, though. Thank you so much in advance to anyone who answers!!

Pauline Tze 3B
Posts: 57
Joined: Sat Jul 09, 2016 3:00 am
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Re: Quiz 1 Prep: Fall 2015, Question #1  [ENDORSED]

I'm not sure where you got the .6 from, or even what molarity equation you used, but I think it'd be a good idea for you to review Mixtures and Solutions Fundamentals Section G.

You're supposed to use (Molarity)initial(Volume)initial = (Molarity)final(Volume)final
In this problem, 2.00 M is the initial molarity, 0.650 M is the final molarity, and 250 mL is the final volume. Using this information, you should be able to find the right answer.

Hope that helps!!