A solution contains 30% alcohol by weight.How much more alcohol must be added to 100g of the solution so that the percentage of alcohol may become 50%?   

Expert Answers
tiburtius eNotes educator| Certified Educator

We can calculate mass percentage of alcohol in a solution this way


where `m_a` is mass of alcohol, `m_s` ` `  is mass of whole solution and `p` is percentage.

So if solution of 100g contains 30% of alcohol it follows that

`30=(100 m_a)/100`

`m_a=30`g  <-- current mass of alcohol in the solution

Now to get solution with 50% of alcohol we will add `x` grams of alcohol so we have






So we need to add 40g of alcohol to the solution to get solution with 50% of alcohol.

pramodpandey | Student

Alcohal in 100 solution is= 30%100=30g

let x grams alcohoal added to solution to make it 50% alcohol.

by given condition

50% of (100+x)=30+x




40g  alcohal must be added to make 50% solution.