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Question

To prepare a solution for which you need to know the concentration accurately, you weigh out 4.2079g of sodium chloride and dissolve it in about 40cm3 of water in a beaker. You want to make this up to a final volume of 100cm3 of water, do you:
i) add water up to the 100cm3 line;
ii) transfer the solution into a measuring cylinder and add water up to the 100cm3 line;
iii) transfer the solution into a 100cm3 volumetric flask and add water to the mark;
iv) pipette 60cm3 of water into the solution.
Explain your choice.

Answer 1

i) you don't want to use the beaker because it is inaccurate
ii) or the cylinder for same reason
iii) do this, generally very accurate, usually says how accurate or actual volume on the side or bottom of them.
iv) don't know very well the original 40cm3, could be 41 could be 39, 35...

Answer 2

the answer is (iii)
It is because measuring from a volumetric flask ismore accurate (you can measure upto 0.01 cm3 )than a beaker or a measuring cylinder

the 4th one is not suitable as you have used ABOUT 40cm3 to dissolve the NaCl which means it can be 40.10 cm3 or 39.9 cm3

Answer 3

1-2-3 are all the same thing -
you are adding up to the 100cm3 line

only #4 is different

by adding 60 - you now have 100cm3 of water

FINAL ANSWER!

Answer 4

answer iii volumetric flasks are much more accurate