Answer :
Answer:
[tex]\approx 6.667ml[/tex]
Explanation:
Let [tex]x[/tex] be the quantity of pure acid that you must add, and [tex]y[/tex] the total quantity of acid in the solution final solution. Then when you add x to the solution the 25% of it will be [tex]y[/tex]:
[tex]y=.25(50+x)[/tex]
And [tex]y[/tex] is also equal to 15% of the solution of 50ml plus [tex]x[/tex].
[tex]y=.15(50)+x[/tex]
Equalize these two equations to form a new without y and solve:
[tex].25(50+x)=.15(50)+x\\12.5+0.25x=7.5+x\\12.5-7.5=x-0.25x\\5=0.75x\\x=5/0.75\\x=6\frac{2}{3}\approx 6.667ml[/tex]