Question

How do I calculate the concentration of a bottle of hydrogen peroxide marked 3%?

Answer 1

Also, how do I calculate the concentration for:
1) A (which contains 5ml hydrogen peroxide and 10ml water)?
2) B (which contains 7.5ml hydrogen peroxide and 10ml water)?

Answer 2

When you said in your question 3%, that it is a form of express the concentration of a solution, it that's means that you have 3g of solute in 100 g of solution.
Then I think that want you want to mean is the concentration in moles per liter.
In this case, you have to assume that your solution has a density of 1.00 g/mL and calculate how many moles of H2O2 you have in 3g of the solution. Then calculate how many moles you would have in one liter of solution.

For the other questions you supposed to use the formula M1V1=M2V2 for calculate the concentration of a dilution, but also you didn't include how concentrated are your 5mL or your 7.5mL.

I will assume that you want to make that dilutions from the original 3% solution. Then again, you want to know the concentration in moles/L (Molarity) or in %.

If it is in % you just apply the formula M1V1=M2V2 where M1 and V1 are the concentration and volume of the concentrated solution and M2 and V2 the concentration and volume of the final solution.

If it is in Molarity you should use the value of concentration calculated in the first part of the problem

Answer 3

Thank you very much!

"I will assume that you want to make that dilutions from the original 3% solution"
Yes, that's correct.

This is actually a bio lab where the aim is to investigate the effects of substrate conc. on an enzyme catalysed reaction. By the way, this has been confusing me, what's the difference between M and mold/dm3?

Answer 4

*mol/dm3 sorry

Answer 5

in number is exactly the same

Answer 6

okay. Thanks :)

Answer 7

or 1ml = 1cc = 1cm^3