Question

solution is prepared by adding 18 mL of 0.200 M Fe(NO3)3and 2 mL of 0.0020 M KSCN. Calculate the initial concentrations of Fe3 and SCN-in the solution

Answer 1

Answer : The initial concentration of $Fe^{3+}$ and $SCN^-$ in the solution are, 0.200 M and 0.0020 M respectively.

Explanation :  Given,

Concentration of $Fe(NO_3)_3$ = 0.200 M

Concentration of $KSCN$ = 0.0020 M

As, 1 mole of  $Fe(NO_3)_3$ dissociate then it gives 1 mole of $Fe^{3+}$ ion and 3 moles of $NO_3^-$ ion.

So, 0.200 M of  $Fe(NO_3)_3$ dissociate then it gives 0.200 M of $Fe^{3+}$ ion and (3×0.200 M) of $NO_3^-$ ion.

and,

As, 1 mole of  $KSCN$ dissociate then it gives 1 mole of $K^{+}$ ion and 1 mole of $SCN^-$ ion.

So, 0.0020 M of  $KSCN$ dissociate then it gives 0.0020 M of $K^{+}$ ion and 0.0020 M of $SCN^-$ ion.

Thus, the initial concentration of $Fe^{3+}$ and $SCN^-$ in the solution are, 0.200 M and 0.0020 M respectively.