Question

Need help with a molarity question!!

Answer 1

What is the question? But before anything, this should help: http://erhs.rcsnc.org/UserFiles/Servers/Server_4766394/Image/Donna%20Scofield/mole%20conversion%20map.bmp

Answer 2

50ml of 4 M H2SO4 is diluted to 250 ml. If 25ml of the diluted solution is taken, how many moles of H2SO4 are in the sample?

Answer 3

Well the number of moles of a solute in solutions never change no matter how much it is diluted or concentrated. (Note that this is as long as no solution with solutes is taken away or added) The only thing that changes is the concentration. So, if you take 25 out of 50+250 of solution, what number of moles will be in that portion?

Answer 4

4?

Answer 5

I'm sorry if that was a stupid answer, haven't really done this in a while

Answer 6

4 moles will be in that 50+250 solution after dilution. If I am doing this right, if you take 25ml out it will be a fraction of 25/(50+250) of the number of mole.

I will try to get someone to check for me. Somehow I confused myself.

Answer 7

did you get 0.0833 mole?

Answer 8

That is the fraction. So you want that fraction of 4 moles.

Answer 9

okay, so then I would just multiply my answer by four, yeah?

Answer 10

If my method is actually correct, yeah.

Answer 11

cool, Thanks so much! it helped

Answer 12

Was it correct? And if so, do you know what and why we did what we did?

Answer 13

Won't find out till Monday. I can see that you had used the formula to get that answer

Answer 14

There wasn't a really formula in this one. You just have to remember that the number of moles doesn't change with volume. The thing that changes is the concentration.

Answer 15

alright then, I'll try to remember that. Thanks again

Answer 16

You're welcome and welcome to OS again!

Answer 17

Talk to ya later!