Dilution
Dilution calculations are common in both chemistry
courses and in lab. The calculations are actually quite
simple to perform as they only use one equation M1V1
= M2V2 where
M1 = the initial concentration
V1 = the initial volume
M2 = the final concentration
V2 = the final volume
The concentration is usually given in M (mol/L) and the
volume can be in any unit you want, as long as you use the same units
for V1 and V2.
Example Question:
Mixing
H2SO4?
"What volume, in mL, of
concentrated sulfuric acid
(18.0 M H2SO4) is needed
to prepare 2.50 L of a 1.00 M
solution? How would I do this problem?"
Answer:
We'll start with our equation
M1V1 = M2V2
where M1 = the initial concentration (18.0M)
V1 = the volume of that solution you will need
M2 = the final concentration you want (1.00M)
V2 = the final volume of solution you want
(2500mL, or 2.5L)
so you plug the numbers in, we're going to use 2500mL so it gives us
our answer in mL.
18.0 (V1) = 1.00 (2500mL)
V1 = 2500 / 18
V1 = 138.89 mL
So you would measure out 138.89 mL of sulfuric acid and dilute to
2500mL (Add 2361.11 mL of water)
*** VERY IMPORTANT - do not pour water into a
concentrated acid solution. The mixing of water and a
concentrated acid is an exothermic process (creates heat).
Instead, get about 1/2 to 3/4 of the water you need, add the
concentrated acid to that, then finish diluting with the rest of your
water.
Did I miss something?
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me know
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