?

AP® Chemistry

Free Version

Upgrade subject to access all content

Moderate

Redox Titration

APCHEM-TQDOD0

A titration is carried out using 0.010 M $KMn{ O }_{ 4 }(aq)$ in the presence of excess sulfuric acid to determine the concentration of iron(II) ion in a solution of iron(II) sulfate ($FeS{O}_{4}$). The balanced equation for the reaction is:

$$2KMn{ O }_{ 4 }(aq)+10FeS{ O }_{ 4 }(aq)+8{ H }_{ 2 }{ SO }_{ 4 }(aq)\rightarrow 5{ Fe }_{ 2 }{ \left( { SO }_{ 4 } \right) }_{ 3 }(aq)+2MnS{ O }_{ 4 }(aq)+{ K }_{ 2 }{ SO }_{ 4 }(aq)+8{ H }_{ 2 }O(l)$$

If 25 mL of the $FeS{O}_{4}$ solution requires 37 mL of the permanganate titrant, which of the following expressions CORRECTLY gives the concentration of ${Fe}^{2+}$, in mol/L, in the iron(II) sulfate solution?

The molar masses of the reactants and products are:

  • $KMn{ O }_{ 4 }$: 158 g/mol
  • $FeS{O}_{4}$: 152 g/mol
  • ${ Fe }_{ 2 }{ \left( { SO }_{ 4 } \right) }_{ 3 }$: 400 g/mol
  • $MnS{ O }_{ 4 }$: 151 g/mol
A

$\cfrac { 0.037\times 0.010\times 5 }{ 0.025 } $

B

$\cfrac { 0.025\times 0.010\times 5 }{ 0.037 }$

C

$\cfrac { 0.025\times 5 }{ 0.037\times 0.010 }$

D

$\cfrac { 0.037\times 5\times 400 }{ 158\times 0.025 } $