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### Test 1 Question Q2B

Posted: **Tue Nov 07, 2017 2:32 am**

by **Paula Dowdell 1F**

Hi! The question is how many milliliters of the stock solution would you need to use to make 250 mL 0.650 M NaOH solution.

How come the answer is 81.2mL? Thanks!

### Re: Test 1 Question Q2B

Posted: **Tue Nov 07, 2017 7:12 am**

by **Clara Rehmann 1K**

If you know the molarity of the stock solution, you can use the equation MiVi = MfVf, with Mf being .650M and Vf being .25 L.

### Re: Test 1 Question Q2B

Posted: **Thu Nov 09, 2017 4:31 pm**

by **Sarah Brauer**

The units in molarity is Liters not milliliters right?

### Re: Test 1 Question Q2B

Posted: **Thu Nov 09, 2017 4:55 pm**

by **Kourtney Nham 1L**

The molarity of the stock solution was 2.00 M NaOH. So you'd set up the equation as (2 M)(Vi)=(.650 M)(.250 L). Vi=.08125 L which is equivalent to 81.2 mL (only 3 sig figs are given, and numbers ending with 5 are rounded to the closest even number).

### Re: Test 1 Question Q2B

Posted: **Sun Dec 10, 2017 1:52 pm**

by **Sonja Kobayashi 1H**

Yes the units for molarity are in liters, however I believe if the question is asking for the final volume in milliliters and you are given milliliters you can keep the number in milliliters so you do not have to convert the answer at the end!