Question

A chemist has 3 liters of a 40% alcohol solution. How much should he pour out and then replace with pure alcohol to get 3 liters of a 75% alcohol solution?

Answer 1

Given:

3 liter of a 40% alcohol solution.

`\begin{gathered} =3*(40)/(100) \\ =3*0.4 \\ =1.2 \end{gathered}`

Then here 1.2 liter of alcohol.

3 liter of a 75% alcohol solution.

`\begin{gathered} =3*(75)/(100) \\ =2.25 \end{gathered}`

So 2.25 liter pure alcohol required in 3 liter of solution.

for add 2.25 liter alcohol solution

`\begin{gathered} =2.25-1.2 \\ =1.05 \end{gathered}`

So the 1.05 liter alochol required to maintain the 75% alcohol solution.