Question

How many grams of a stock solution that is 92.5 percent H2SO4 by mass would be needed to make 250 grams of a 35.0 percent by mass solution? Show all of the work needed to solve this problem.

Answer 1

M1m1 = M2m2

where M1 is the concentration of the stock solution, m1 is the mass of the stock solution, M2 is the concentration of the new solution and m2 is its new mass.

M1m1 = M2m2

.925(m1) = .35(250)

m1 = 94.59 g

Answer 2

Answer: 94.59 grams of 92.5 % $H_2SO_4$ by mass solution will be needed.

Explanation:

Mass of sulfuric acid is 250 grams of 35 % by mass solution:

$35=\frac{x}{250 g}\times 100$

$x=87.5 g$

Mass of $H_2SO_4$ in 250 g of 35 % solution = 87.5 g

Mass of 92.5 % $H_2SO_4$ needed to make 35 % by mass solution.

$92.5=\frac{87.5 g}{\text{mass of the solution required}}\times 100$

Mass of the solution required = 94.59 g

94.59 grams of 92.5 % $H_2SO_4$ by mass solution will be needed.