Commercially available concentrated sulfuric acid is 18.0 M H2SO4. What volume of concentrated H2SO4 would I use in order to make 3.00 L of a 4.0 M stock solution?
1 Answer
You would need 0.67 liters of the concentrated acid.
This question demonstrates a technique that chemists use on a regular basis; it is called dilution.
You will use the equation (M1)(V1) = (M2)(V2)
The original concentration x initial volume = final concentration x final volume.
In this example, the original concentration is the concentration of the concentrated sulfuric acid which is 12 Molar which is M1 and the final diluted concentration is 4 Molar (M2) with a final volume of 3.00 liters.

To solve for V 1 , multiply 4.0 Molar by 3.00 L and divide by 18.0 M

#V _1# =#(M_2 . V _2) / M _1# 
#V _1# =#( 4.0 M . 3.00 L ) / (18.0 M# #V _1# . =#0.67 L#

This means that you need to dilute 0.67 liters of the original stock solution of concentrated acid and add water until it is diluted to 3.00 liters.
Here is a video which illustrates another example using (M1)(V1) = (M2)(V2)