Question

How would you prepare 455 g of aqueous solution that is 6.50% sodium sulfate Na2SO4 by mass?

percent by mass = grams/100 g solution.

X grams/455 = 0.065
solve for X. Subtract 455-X to calculate how much water must be added.

ok i got -454.935 is this right

Answer 1

Does it make sense to you that you can subtract 454.935 g from 455 g to make a 6.5% solution? What's X? X is the amount of Na2SO4 that must be added to some water to make the 6.5% solution of Na2SO4.

Answer 2

so then i did it wrong... :( is it 142g for the Na2SO4 that needs to be put into there

Answer 3

No.
(X/455) = 0.065
X = 455*0.065 = ??
Grams water = 455 - ?? = xx

Then check yourself.
(??/455)*100 = 6.5%

Answer 4

29.575/455*100=6.5%
Yay :)

Answer 5

I would round the 29.575 g Na2SO4 to to 29.6 grams. Remember the question. The question was how to prepare 455 g of a solution that was 6.5% Na2SO4. That answer is to dissolve 29.6 g Na2SO4 in 455-29.6 g water (which would make a total of 455 g).