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 M_{1}V_{1}
= M_{2}V_{2 }where
M_{1} = the initial concentration
V_{1} = the initial volume
M_{2} = the final concentration
V_{2} = 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 V_{1} and V_{2}.
Example Question:
Mixing
H_{2}SO_{4}?
"What volume, in mL, of
concentrated sulfuric acid
(18.0 M H_{2}SO_{4}) 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
M_{1}V_{1} = M_{2}V_{2}
where M_{1} = the initial concentration (18.0M)
V_{1} = the volume of that solution you will need
M_{2} = the final concentration you want (1.00M)
V_{2} = 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 (V_{1}) = 1.00 (2500mL)
V_{1} = 2500 / 18
V_{1} = 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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