absoprtion questions?

Question

1. What volume of 0.2 M Fe(NO3)3 is needed to make 50 mL of 0.002 M Fe(NO3)3?
2. WHat are the concentrations of Fe+3 and NO-3 in a 0.2 M Fe(NO3)3 solution?
3. If 5 mL 0,002 M Fe(NO3)3 is mixed with 5 mL 0.002 M KSCN calculate the initial concentration of Fe+3 and SCN- in the solution

Answer 1

These are not absorption questions. In no instance are you addressing absorption.

These are high school chemistry homework quesitons. If you are taking freshman college chemistry you should have mastered this in high school and definately need to master it now. You have not mastered your lesson and need to get the assignment done. How will you end up passing the final exam?

Look at question # 1, youi need to make 50 ml of 0.002 M Ferric Nitrate solution from 0.2 M. How many mmoles of Ferric Nitrate is needed? Easy - 0.002 M means 0.002 mmole / ml so you need 50 ml x 0.002 mmole/ml or 50x0.002 mmoles. Now how many ml of 0.2 M feric nitrate solution gives you 50x0.002 mmoles? Remember M means mmole/ml so (50x0.002 mmoles)/(0.2 mmoles/ml) = [(50x0.002)/0.2] ml. Work with the units and treat them just like any algebraic equiation and all falls into place.

Now understand what I did, why I did it, and why it works. Once this is mastered the problems can be done.

By the way, I will let you do the actual number crunching.

Answer 2

1. C1V1 = C2V2
(0.2) V1 = (0.002)(50)
volume = 0.5 ml

2. no. of moles of Fe3+ : NO3- = 1:3
So concentration of Fe3+ is 0.2mol/ml
concentration of NO3- is 0.6 mol/ml

3. this question quite funny... isn't the info given already the initial concentration of Fe+3 and SCN- in the solution?

If so conc of Fe3+ = 0.002mol/ml
conc of SCN- = 0.002mol/ml

not very sure on Q3.