Test 1 Question Q2B

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Paula Dowdell 1F
Posts: 72
Joined: Tue Nov 15, 2016 3:00 am

Test 1 Question Q2B

Postby Paula Dowdell 1F » Tue Nov 07, 2017 2:32 am

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!

Clara Rehmann 1K
Posts: 53
Joined: Fri Sep 29, 2017 7:03 am

Re: Test 1 Question Q2B

Postby Clara Rehmann 1K » Tue Nov 07, 2017 7:12 am

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.

Sarah Brauer
Posts: 17
Joined: Fri Sep 29, 2017 7:06 am

Re: Test 1 Question Q2B

Postby Sarah Brauer » Thu Nov 09, 2017 4:31 pm

The units in molarity is Liters not milliliters right?

Kourtney Nham 1L
Posts: 20
Joined: Fri Sep 29, 2017 7:04 am

Re: Test 1 Question Q2B

Postby Kourtney Nham 1L » Thu Nov 09, 2017 4:55 pm

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).

Sonja Kobayashi 1H
Posts: 20
Joined: Fri Sep 29, 2017 7:04 am

Re: Test 1 Question Q2B

Postby Sonja Kobayashi 1H » Sun Dec 10, 2017 1:52 pm

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!


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