Dissolving a chemical

[PRIYA RAWAL]

I want to ask,
Is there is any difference between

1. to dissolve a chemical directly in 1000ml water

2. dissolving a compound in little quantity of water and then making its volume upto 1000ml.

is it cause any change???

thanks...

[luisillo]

Yes it does. The chemical will raise the volume of the solution and it won't be 1000 ml anymore, which ultimately change the final concentration of the chemical in the solution.

The best way to prepare a solution with a know concentration of a certain chemical (powder) is to weight the needed amount of the chemical and then dissolve it in a no more than 80% of the total volume of solvent (water, etOH or whatever). Once your chemical has completely dissolved, raise the volume to, in this case, 1000 ml.

[danfive]

Originally Posted by luisillo

Yes it does. The chemical will raise the volume of the solution and it won't be 1000 ml anymore, which ultimately change the final concentration of the chemical in the solution.

The best way to prepare a solution with a know concentration of a certain chemical (powder) is to weight the needed amount of the chemical and then dissolve it in a no more than 80% of the total volume of solvent (water, etOH or whatever). Once your chemical has completely dissolved, raise the volume to, in this case, 1000 ml.

The post above is absolutely correct.
Some dunces tend to disagree when the subject comes up, because they don't understand the concept of mass.