Units when calculating volume

Moderators: Chem_Mod, Chem_Admin

janessadai 1F
Posts: 14
Joined: Fri Sep 28, 2018 12:18 am

Units when calculating volume

Postby janessadai 1F » Tue Oct 02, 2018 11:32 pm

I understand that Dr Lavelle mentioned during the lecture that we have to use the units "L" for volume in our workings when using the equation Minitial Vinitial = Mfinal Vfinal (because the units for M is mol/L), but seeing that the equation is almost like a ratio between volume and molarity, won't using "ml" for calculations of volume just mean that the answer will be in "ml"?

Meghanhe1l
Posts: 60
Joined: Fri Sep 28, 2018 12:17 am

Re: Units when calculating volume

Postby Meghanhe1l » Tue Oct 02, 2018 11:44 pm

When we are calculating volume we use the equation M1V1=M2V2, where M=mol/L and we are given both M1 and M2 as well as one of the Vs. Because we are using mol/L in our calculations, we must remain uniform and keep all our calculations in L.

ian_haliburton_1f
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

Re: Units when calculating volume

Postby ian_haliburton_1f » Tue Oct 02, 2018 11:50 pm

When solving for a value using this equation, you will need to know three other values already. So, one of the known values needed to solve will always be a concentration. This value is given in terms of moles per liter, so any other values in terms of mililiters to the equation would be off the scale implied by the unit M (moles per liter).

Carine Tamamian 2B
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

Re: Units when calculating volume

Postby Carine Tamamian 2B » Tue Oct 02, 2018 11:58 pm

Molarity is always given in mol/L. In a problem if you're given a value for molarity, it will be in the units mol/L, so it becomes a problem when you don't convert to liters since now you're using two different units. So, I'd say convert any given volume to Liters if you're given a value for Molarity.
Keeping the volume units the same will give the actual correct answer.

Katie_Duong_1D
Posts: 69
Joined: Fri Sep 28, 2018 12:27 am

Re: Units when calculating volume

Postby Katie_Duong_1D » Wed Oct 03, 2018 2:43 pm

Molarity (M) represents moles of solute (mol) per volume of solution (L). M = mol/L. Because molarity is expressed in terms of moles and liters, it is much easier to keep units consistent, so you can cancel out units when cross multiplying.

If the volume is given in millimeters (mL), I would convert it to L by multiplying the volume by 10^3 because 1 L = 1000 mL = 1 x 10^3 mL.

For example, 3.5 mL = 3.5 x 10^3 L.

I hope this helps!


Return to “Molarity, Solutions, Dilutions”

Who is online

Users browsing this forum: No registered users and 1 guest