Question

If you mix 20.0mL of a 3.0M solution with 30mL of a 5.00M solution, determine the concentration in molarity of the new solution.

Answer 1

Solution 1: 20.0 mL x 3.0 M = ?1
Solution 2: 30.0 mL x 5.0 M = ?2

New concentration = ?1 + ?2

Answer 2

Isn't this less than the original concentrations?

Answer 3

First, convert mL to L:

20mL=0.0200L and 30.0mL=0.0300L


Solve for moles:

M=moles/Volume (L) so, moles=M*Volume(L)


New Molarity=Total moles/Total Volume

M=[(0.0200L)*(3.0 M)+(0.0300L)*(2.0M)]/(0.0200L+0.0300L)

Answer 4

I'll get in on the fray here. Irving has it wrong. Devron made a typo. I've copied Devron's work and replaced the typo part with a bold 5.0
M=[(0.0200L)*(3.0 M)+(0.0300L)*(<b>5.0M</b>)]/(0.0200L+0.0300L)

<b>The answer comes out to be about 4.2 which is the weighted average between the 3.0 and 5.0 M which makes sense. You know it must be somewhere between 3.0 M and 5.0 M. </b>