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### Topic: Concentration Question (mol/L obviously... lol)  (Read 7058 times)

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#### sundrops

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##### Concentration Question (mol/L obviously... lol)
« on: October 05, 2005, 10:47:58 PM »
ok so I'm preparing solutions. I have 10mL of 0.150M Fe3+ and 5mL of 0.0005M  SCN- and 10mL of 0.10 M HNO3

my question is, how do I determine the concentration of Fe3+ in the solution?

0.150 mol/L * 0.01L = 0.0015mol Fe3+
o.oo15mol Fe3+ / .025L = 0.06M Fe3+

#### sundrops

• Guest
##### Re:Concentration Question (mol/L obviously... lol)
« Reply #1 on: October 05, 2005, 10:49:21 PM »
well apparently pink writing is UNREADABLE - so I'll copy and paste my post

ok so I'm preparing solutions. I have 10mL of 0.150M Fe3+ and 5mL of 0.0005M  SCN- and 10mL of 0.10 M HNO3

my question is, how do I determine the concentration of Fe3+ in the solution?

0.150 mol/L * 0.01L = 0.0015mol Fe3+
o.oo15mol Fe3+ / .025L = 0.06M Fe3+

#### mike

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##### Re:Concentration Question (mol/L obviously... lol)
« Reply #2 on: October 05, 2005, 10:52:18 PM »
yes.

can also use:

C1V1 = C2V2

C = concentration (1 = initial, 2 = final)
V = volume (1 = initial, 2 = final)
There is no science without fancy, and no art without facts.

#### sundrops

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##### Re:Concentration Question (mol/L obviously... lol)
« Reply #3 on: October 05, 2005, 11:02:18 PM »
just checking

thanks!

#### sundrops

• Guest
##### Re:Concentration Question (mol/L obviously... lol)
« Reply #4 on: October 06, 2005, 01:26:38 AM »
alrighty so we determined how to find the concentration of Fe3+ and I found the concentration of SCN- in the same way.

But now I need to determine the final concentration of FeSCN2+ but I'm not sure how to go about finding it.

any suggestions?

#### sundrops

• Guest
##### Re:Concentration Question (mol/L obviously... lol)
« Reply #5 on: October 06, 2005, 01:28:52 AM »
I know that all the SCN- will be used in forming the FeSCN2+, does that have anything to do with the final concentration of this compound?

#### Borek

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##### Re:Concentration Question (mol/L obviously... lol)
« Reply #6 on: October 06, 2005, 05:00:26 AM »
well apparently pink writing is UNREADABLE - so I'll copy and paste my post

So use black. I know it is boring, but it is perfectly readable

You may assume that SCN- reacted completely with Fe3+ - and treat is as a limiting reagent question. Then check if the change in the final concentration of Fe3+ (after dilution) is not below the significant digits level.
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#### sundrops

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##### Re:Concentration Question (mol/L obviously... lol)
« Reply #7 on: October 06, 2005, 11:31:24 AM »
but how do I determine [FeSCN2+]?
I cannot treat it as a limiting reactant if I do not have the concentration of the product?
product being: [FeSCN2+]

#### sundrops

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##### Re:Concentration Question (mol/L obviously... lol)
« Reply #8 on: October 06, 2005, 11:40:23 AM »
does [SCN-] = [FeSCN2+]?

#### Borek

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##### Re:Concentration Question (mol/L obviously... lol)
« Reply #9 on: October 06, 2005, 11:51:45 AM »
does [SCN-] = [FeSCN2+]?

Write down reaction equation between Fe2+ and SCN-. Amounts of both substrates are given in the question. This IS a limiting reagent question - you just have to convert concentrations to moles and moles to concentrations when needed.
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