Wednesday, January 6, 2010

How do I figure out this chemistry problem?

Calculate the mass of solution required to prepare a 6.0% w/w tile and houshold cleaner solution containing 15.5g of sodium phosphate.How do I figure out this chemistry problem?
i think you would do 15.5 divided by .06. so basically my way is fastest instead of 3rd oneHow do I figure out this chemistry problem?
If you make a 6% w/w solution of sodium phosphate. you must know:

%w/w = mass solute/mass solution

let the mass of solute = X

6/100 = X/100+X

100X = 600+6X

94X = 600

X = 6.383g

Mass of solution = 106.383g

Check: 6.383/106.383*100 = 6.00% solution

But you want to use 15.5g sod phosphate

Mass of solution = 15.5/6.383*106.383

Mass of solution = 258.333g solution

Check: 15.5/258.333*100 = 6.00%

You must dissolve 15.5g sod phos in sufficient water to make a final solution with a mass of 258.333g
15% w/w means 15% of the solution is sodium phosphate, by weight (actually mass). Let ';x'; be the mass of water needed to make the solution.

6.00 = 15.5 g

------- ------------

100 x +15.5 g

The mass of the solution is (x + 15.5 g).

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