# What mass of potassium dichromate is required to oxidize an 100*mL volume of Fe^(2+) solution whose concentration is 0.10*mol*L^-1?

Feb 17, 2017

$\text{Approx. 1/2 a gram of potassium dichromate............}$

#### Explanation:

We need an oxidation equation:

$F {e}^{2 +} \rightarrow F {e}^{3 +} + {e}^{-}$

And a reduction equation:

$C {r}_{2} {O}_{7}^{2 -} + 14 {H}^{+} + 6 {e}^{-} \rightarrow 2 C {r}^{3 +} + 7 {H}_{2} O \left(l\right)$

Overall:

$C {r}_{2} {O}_{7}^{2 -} + 6 F {e}^{2 +} + 14 {H}^{+} \rightarrow 2 C {r}^{3 +} + 6 F {e}^{3 +} + 7 {H}_{2} O \left(l\right)$

$\text{Moles of}$ $F {e}^{2 +} :$

$100 \times {10}^{-} 3 \cdot L \times 0.10 \cdot m o l \cdot {L}^{-} 1 = 0.010 \cdot m o l$

And thus we need $\frac{0.010 \cdot m o l}{6} \times 294.18 \cdot g \cdot m o {l}^{-} 1 = 0.490 \cdot g$ ${K}_{2} C {r}_{2} {O}_{7}$.