calculate concentration ?? (1 Viewer)

[sando]

this was taken from 2004 hsc/

Beaker initially contained 250.0 mL of 0.050 mol L copper sulfate solutioon. The red-brown deposit was removed from the piece of zinc metal and dried. It was found to weigh 0.325g. Calculate the concentration of copper sulfate solution remaining in the beaker.


this confused me cos i think it contains unnecessary info.

is the answer just... (or am i terribly wrong)


concentration= #mol CuS04 x Volume (L)

= 0.050 x 0.25

= 0.0125 molL


??????

 

[Nodice]

First we calculate the number of mols that are in the original solution:
cV=n
nCuSO4= 0.25 x 0.05 = 0.0125 mols in the solution
Then we work out how many mols of the copper was taken out from the zinc
nCu = m/mm
nCu = 0.325/63.546 = 5.11 x 10^-3 mols
Now we minus original amount of mols from the final amount: 0.0125- 0.00511 = 0.00739
n=cV = 0.00739 x 0.25 = 0.0018475 mol/L
= 1.85x10^-3 mol/L (adjusting sig figs)