## dddan 3 years ago please help!; Assuming additivity of volumes, what is the concentration of KBr(in moles/L) in a solution prepared by mixing 2.50x10^2 of 0.0600 Molarity of KBr with 5.00x10^2 ml of 0.0830 Molarity?

1. ethayer

is the first one in mL too?

2. dddan

yea the 2.50x10^2 is in ml

3. ethayer

I think this is how you do it. 1st: change the mL into L (since M is in mol/L) 2nd: calculate the number of moles of KBr in each solution (M * L from above) 3rd: add the 2 numbers for moles together 4th: add the 2 numbers for volume together 5th: divide since you now have total moles and total volume (M = moles/L)

4. ethayer

let me know what you get.

5. dddan

alright

6. ethayer

just a way to check, your answer should be in-between the two given molarities since you are mixing them together and it should be a little closer to the larger molarity since you start with more of it.

7. dddan

alright i got a 5.2 Molarity does this sound right?

8. ethayer

try again. It should be between .6M and .083M since those are the values you started with and you are mixing the same compound. What did you get for your 2 new volumes?

9. ethayer

^sorry, .06M not .6

10. dddan

.25L and .5L

11. ethayer

great! now what about for the moles of KBr found in each solution (molarity * liters = moles)?

12. dddan

i got .15 and 0.0415....

13. ethayer

the first one should be .015...

14. dddan

alright hold on

15. dddan

16. ethayer

alright! now when you add up your volumes what do you get? also what do you get when you add up the moles?

17. dddan

alright then i got .075 as final answer

18. ethayer

correct! .0565mol/ .75L

19. dddan

thanks so much!!!

20. ethayer