# Question 6ba0b

Apr 15, 2017

Yes, it is a double displacement reaction.

#### Explanation:

The balanced equation is

3("NH"_4)_2stackrelcolor(blue)("+2")("Fe")("SO"_4)_2 + 2"K"_3 stackrelcolor(blue)("+3")("Fe")"(CN)"_6 → stackrelcolor(blue)("+2")("Fe"_3)[stackrelcolor(blue)("+3")("Fe")"(CN)"_6]_2 + 3("NH"_4)_2"SO"_4 + "3K"_2"SO"_4

Note that the iron is present in two different oxidation states.

Also, the ${\left({\text{NH"_4)_2"Fe"("SO}}_{4}\right)}_{2}$ is just a double salt of ("NH"_4)_2"SO"_4and ${\text{FeSO}}_{4}$.

The ammonium sulfate doesn't take part in the reaction, so we can rewrite the equation as

underbrace(3stackrelcolor(blue)("+2")(color(red)("Fe"))"SO"_4)_color(red)("iron(II) sulfate") + underbrace(2color(blue)("K")_3 stackrelcolor(blue)("+3")("Fe""(CN)"_6))_color(red)("potassium hexacyanoferrate(III)") → underbrace(stackrelcolor(blue)("+2")(color(red)("Fe"))_3[stackrelcolor(blue)("+3")("Fe")"(CN)"_6]_2)_color(red)("iron(II) hexacyanoferrate(III)") + underbrace(3color(blue)("K")_2"SO"_4)_color(red)("potassium sulfate")#

We see that the $\text{K"^"+}$ and $\text{Fe"^"2+}$ ions have changed partners.

This is the classic definition of a double decomposition reaction.