Solutions and Concentration - Making a Solution

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 Our next step will be to make a solution of a desired concentration. For this, we need to:

  • calculate the amount (number of moles) that we need, then
  • calculate the mass of solute we need to dissolve.



We may not measure our mass out exactly. That is okay, so long as we record the mass we did use to three significant figures. We then can work out the exact concentration of the solution we did actually make.

For example, let's say the closest we could get to 2.65g was 2.68g:

n = m/MR
n = 2.68/105.99
n = 0.0253 mol (3s.f.)

c = n/V
c = 0.0253/0.2500
c = 0.101 mol L-1 (3s.f.)

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