What mass of 4.00% NaOH solution by mass contains 15.0g of NaOH?

Question

Please explain how to do this problem.

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Answer 1

% by mass = mass solute x 100 / mass solution
4.00 % = 15.0 g x 100 / mass solution
mass solution = 15.0 x 100 / 4.00 = 375 g

Answer 2

1% = 1g NaOH per 100 mls,
4% = 4g / 100 mls,
= 1 g / 25 mls,
= 1 *15 g NaOH in 15*25 mls solution
= 15g 375 mls solution
We now multiply the result by 1.0443 being the specific density
of 4% w/w NaOH : 375*1.0443 = 392 g.
ANS: 392 g 4% NaOH (w/w) contains 15g NaOH.

Answer 3

100g solution contains 4.00 g NaOH.
g solution needed = 15.0 gNaOH x 100g solution/4.00 g NaOH
g solution needed =3.75 x 100 = 375 g solution.