how do i figure out the dilutions of 1.5L of a 15.0% (v/v) NaCl/water solution, what would the concentration of NaCl be if you added 3.0L of water
2 answers
double amount of water, same NaCl, half the concentration
I have a problem with the problem and I also have a problem with the answer. The answer first.
You aren't doubling the volume. Assuming the volumes are additive, and with this concn NaCl they probably are not, the volume is increased from 1.5L to 4.5 L so the new concn is
15 x (4.5/1.5) = 15 x 1/3 = 5%.
Next the problem with the problem. A 15% v/v makes no sense to me with NaCl a solid. How do you measure, for example, 15 mL of NaCl crystals (and what size are they and all of the complications that go with that). If you made a typo and that is 15% w/v you probably need the densities of the two solution; i.e., before and after dilution.
You aren't doubling the volume. Assuming the volumes are additive, and with this concn NaCl they probably are not, the volume is increased from 1.5L to 4.5 L so the new concn is
15 x (4.5/1.5) = 15 x 1/3 = 5%.
Next the problem with the problem. A 15% v/v makes no sense to me with NaCl a solid. How do you measure, for example, 15 mL of NaCl crystals (and what size are they and all of the complications that go with that). If you made a typo and that is 15% w/v you probably need the densities of the two solution; i.e., before and after dilution.
1 answer