bob800 - 10-1-2011 at 18:12
When following many procedures for experiments, they often call for a "dilute" solution of some chemical, and the exact concentration is not stated.
Obviously this means that the concentration is not critical, but sometimes I have no idea what a "dilute" solution is.
What would a "dilute" solution be for the following chemicals:
-Hydrochloric Acid
-Sulfuric Acid
-Sodium Hydroxide
-Nitric Acid
etc.
Does it vary from chemical to chemical, or does "dilute" usually refer to a rough molarity? I'm guessing most chemicals might be "dilute" at 1M?
Any help would be appreciated!
woelen - 10-1-2011 at 23:16
What is dilute for one experiment may be highly concentrated for another, even for the same chemical.
E.g. I have done experiments with chromium-peroxo complexes and I used solutions of potassium dichromate for these experiments. A concentration of
0.1% already is very high in those experiments if you want to be able to observe colors. In another experiment, where dichromate is used as oxidizer
for some alcohol, a concentration of 2% is considered dilute.
Just as a rule of thumb, when nothing special is stated about the experiment, you may consider a concentration of approximately 1% by weight 'dilute'.
E.g. an experiment asks for 1 small spatula of solid to be added to a few ml of water. Then you will have a few tens of mg in a few ml of water, which
is roughly 1% by weight. But, as I said, this is a very coarse rule.
Similar things can be said for acids and bases. A concentration somewhere between 0.1M and 1 M can be considered 'dilute', but again, this is a coarse
rule and there may be exceptions where a concentration of 0.1M is considered very high.
unionised - 11-1-2011 at 11:39
When I was at school the bottles labelled as, for example, "dilute sodium hydroxide" contained about 2 normal solutions.
http://en.wikipedia.org/wiki/Concentration#Normality
ItalianChemist - 26-1-2011 at 06:11
You can concentrate sulfuric acid only boiling it, until withe smokes of SO3 appears.
The other acid must be distilled, if you want concentrate nitric acid to >90% you must use a dessiccant such as sulphuric acid!
Sodium Hydroxide can be concentrated boiling it and evaporating the water.