5.00mL of .00500 M ferric nitrate is added to 5.00 Ml of nitric acid and 10.0 Ml of .00250 M thiocyanate solution. Calculate the initial FE^3+ concentration before reaction.
I know F3^3+=Cfe-[FESCN^2+]
after that I have no idea what to do.
Help please?? =-(
YOu may have posted only part of the problem BUT the part you posted is the simplest of all and you are making it too complicated.
BEFORE the reaction, the concn Fe^+3 =
M x L = 0.005 M x 0.005 L = ??moles.
What's the volume? 5 mL + 5 mL + 10 mL = 20 mL = 0.020 L.
So (Fe^+3) = ?? moles from above/0.020 L = xx M.
To calculate the initial Fe^3+ concentration before the reaction, you can use the equation given: Fe^3+ = [Cfe] - [FESCN^2+].
First, let's calculate the initial concentration of Fe^3+ ions:
Given:
Volume of ferric nitrate solution = 5.00 mL
Concentration of ferric nitrate solution = 0.00500 M
Using the formula C = n/V, where C is the concentration, n is the amount of substance, and V is the volume, we can calculate the amount of substance (n) of Fe^3+ ions in the ferric nitrate solution.
n = C x V
n = 0.00500 M x 5.00 mL
n = 0.0250 moles
Since the stoichiometry of the equation is 1:1 between Fe^3+ and FeSCN^2+, the initial moles of Fe^3+ ions (n) can be directly taken as the initial moles of Fe^3+ ions.
Now, let's calculate the initial moles of FeSCN^2+ ions (the product) using the other given solutions:
Given:
Volume of nitric acid solution = 5.00 mL
Concentration of nitric acid solution = 5.00 M
n(HNO3) = C x V
n(HNO3) = 5.00 M x 5.00 mL
n(HNO3) = 0.0250 moles
Given:
Volume of thiocyanate solution = 10.0 mL
Concentration of thiocyanate solution = 0.00250 M
n(SCN^-) = C x V
n(SCN^-) = 0.00250 M x 10.0 mL
n(SCN^-) = 0.0250 moles
Since the stoichiometry of the equation is 1:1 between Fe^3+ and FeSCN^2+, the initial moles of FeSCN^2+ ions (n) can be directly taken as the sum of the moles of HNO3 and SCN^-.
n(FeSCN^2+) = n(HNO3) + n(SCN^-)
n(FeSCN^2+) = 0.0250 moles + 0.0250 moles
n(FeSCN^2+) = 0.0500 moles
Finally, substitute the values into the equation Fe^3+ = [Cfe] - [FESCN^2+].
Fe^3+ = 0.0250 moles - 0.0500 moles
Fe^3+ = -0.0250 moles
The initial concentration of Fe^3+ ions before the reaction is -0.0250 M. Note that the negative sign arises because the concentration of FeSCN^2+ is larger than that of Fe^3+ ions, meaning that Fe^3+ is being consumed in the reaction.