SOLUTION: Dear all I have prepared two solutions with different percentage 4% and 2% then I mixed 5 ml from each of the solutions. finally I got 10 ml solution. What is the final concentrat

Question 765923: Dear all
I have prepared two solutions with different percentage 4% and 2% then I mixed 5 ml from each of the solutions. finally I got 10 ml solution. What is the final concentration by %.
Thank you
Answer by MaartenRU(13) (Show Source): You can put this solution on YOUR website!
Let's say it's a solution of sugar. It doesn't matter what it is, but it makes the explanation easier.

You have 5ml of a 4% solution. That means that your 5ml solution is 4% sugar.

4% of 5ml is 4/100 of 5ml, so that's 0.2ml of sugar. (Using a volume for sugar seems a bit weird, but that doesn't matter right now)

In the same way, you have 5ml of a 2% solution. 2% of 5ml is 2/100 of 5ml, so that's 0.1ml of sugar.

Now you're mixing the solutions into one big solution. That means that you're also adding up the sugar. So 0.2ml from the one mixture and 0.1ml from the other, amounts to 0.3ml in the total 10ml solution.

Now we only have to find out what percentage 0.3ml is of 10ml.

That's quite simple! We find the fraction and multiply it by 100. So 0.3/10, that's 0.03. Now multiplying it by 100 gives us 3%.

You might find that this is the average of your 2% and 4%, but watch out! You can only take the average if the solutions have the same volume. See for yourself what happens if you take different volumes. As an exercise, try to work out what solution you will get from mixing 5ml of 2% and 10ml of 5%.
RELATED QUESTIONS
I'm having difficulties with this problem: "A chemist has a 30% acid solution and a... (answered by Paul)

A chemist has a 30% acid solution and a 60% solution already prepared. How much of each... (answered by stanbon,jim_thompson5910)

Hello, Can someone help me with the following: 1. write a quadratic equation having (answered by Alan3354)

Solve the problem by using the Gauss-Jordan method to solve a system of equations.... (answered by josgarithmetic)

Please help!! I need answers to the following questions, I really need to past this... (answered by sudhanshu_kmr)

. Ulysses made two alcohol solutions of different concentrations. When he mixed 4 liters... (answered by ikleyn)

A 5% solution of a drug is to be mixed with some 15% solution and some 10% solution to... (answered by stanbon)

I need for someone to confirm my answer for me. I get so confused with these mixture... (answered by ankor@dixie-net.com)

Consider the equation 4x^2 � 4x + 5 = 0. (i) Compute the discriminant, b2 � 4ac, and... (answered by Nate)