[Toy_03]

A 4.00mL aliquot of 0.001 M NaSCN is diluted to 25.0mL with 0.1 M HNO3

What is the Molar concentration of SCN (negative) in the diluted solution?

IS THE EQUATION: M1V1=M2V2

and is this right

0.001 M Na SCN x .400L=0.1 M HNO3 x .250L
4 x 10^-4=.025
4 x10^-4/.025L=.016M

[mike]

equation is right, calculation is wrong.

1mL = 0.001L

M referes to concentration of SCN not HNO3

[Toy_03]

A 4.00mL aliquot of 0.001 M NaSCN is diluted to 25.0mL with 0.1 M HNO3

What is the Molar concentration of SCN (negative) in the diluted solution?

IS THE EQUATION: M1V1=M2V2

and is this right

0.001 M Na SCN x .00400L=0.1 M HNO3 x .250L
4 x 10^-6=.025
4 x10^-6/.025L=1.6 x 10^-4

Is this right now or its still wrong.  I guess Im kinda confused on converting mL to Liters still.

Another question is : If all of the SCN (negative) is complexed with Fe3+ to FeNCS2+, what is the molar concentration of FeNCS2+

How do you do this???  

[mike]

Your math is wrong.

m1v1 = m2v2

m2 = m1v1/v2

m1 = initial cocentration of SCN
v1 = initial volume of SCN
v2 = vinal volume of SCN

Don't put the HNO3 concentration into this equation!

[mike]

similar post here:

http://www.chemicalforums.com/index.php?board=2;action=display;threadid=5136;start=msg22734#msg22734

[Toy_03]

I cant really understand the other thread.  But I think I may have the problem now:

M2=M1V1/V2

Well For some odd reason I kept getting the same answer like I did before which is 1.6 x 10 ^-4...I really dont know what Im doing wrong.

M2=?
M1=0.001M NaSCN
V1=.00400L
V2=.025

?

[mike]

Yes that answer is correct:

0.00016 mol.L^-1

It is just your working out that doesn't make any sense.