Problema Solution
you have been asked to mix up some 70% isopropyl alcohol solution.you have 95% isopropyl alcohol solution on hand how nuch do you need to have to add to450 ml of pure water to create a 70% alcohol
Answer provided by our tutors
Let y ml of 95% isopropyl alcohol solution required.
If this y ml of 95% isopropyl alcohol solution be added to 450 ml of pure water, then the strength of the solution will be 70%.
Thus,
In 100 ml of 95% isopropyl alcohol solution there is 95 ml isopropyl alcohol.
In y ml of 95% ,, ,, ,, ,, ,, 95y/100 ml isopropyl alcohol.
Now 450 ml of pure water be mixed.
Total volume of the solution = (450+y) ml
volume of isopropyl alcohol in this solution = 95y/100 ml
Therefore, strength of the isopropyl alcohol solution is (95y/100)/(450+y) x 100 %
By question,
(95y/100)/(450+y) x 100=70
or, 95y=450 x 70 +70y
or, 25y=450 x 70
or, y = (450 x 70)/25 = 1260.
We need 1260 ml of 95% isopropyl alcohol solution