Calculating Molarity of FeSCN with Given Moles and Known Reactants

[Prone17]

i combined 5 mL of 0.20 M Fe with 1 mL of 4.0x10^-4 M HSCN and 4 mL of 0.5 M HNO3

i am asked to find the molarity of FeSCN.

i am given this statement: "The concentration of Fe is so high relative to that of HSCN that we can assume that all SCN present is in the complexed form, FeSCN. In other words, HSCN is the liming reagent and the number of moles of HSCN added equals the number of moles of FeSCN that forms."

so i calculated the moles of HSCN by multiplying the molarity by the amount added -> (4.0x10^-4)(0.001) = 4.0x10^-7
apparently this is the same as the moles of FeSCN.

how do i find the molarity of FeSCN? i know the moles, so all i need is the volume (Liters), but i don't know how much to use in the equation... any suggestions?

Thanks

 

[Borek]

You have mixed everything together, right? So what is the final volume of the mixture?

 

[symbolipoint]

A matter of simple accounting for total volume of the prepared solution of FeSCN. Sum of the volumes used in preparing the solution.

 

[Prone17]

the total volume would be 10 mL

thanks guys, i got it from here (hopefully) :D

 

[DeeNos]

for your question. To find the molarity of FeSCN, you can use the formula M = moles of solute / volume of solution (in liters). In this case, you have already calculated the moles of FeSCN to be 4.0x10^-7. To find the volume of the solution, you can add up the volumes of all the reactants used (5 mL + 1 mL + 4 mL = 10 mL = 0.01 L). So, the molarity of FeSCN would be 4.0x10^-7 moles / 0.01 L = 4.0x10^-5 M.

It is important to note that the assumption made in the given statement is crucial in this calculation. If the concentration of Fe was not significantly higher than that of HSCN, then the assumption that all SCN is in the complexed form may not hold true and the molarity of FeSCN would need to be calculated using a different approach.