Question

Is a combination of iron(iii) iodide and sodium hydroxide soluble in water?

Answer 1

No. They react to produce `"Fe(OH)"_3"`, an insoluble solid (precipitate).

Explanation:

Individually, yes. But when mixed, they react in a double replacement reaction to form a precipitate ( insoluble solid resulting from mixing two solutions).

Molecular equation

`"FeI"_3("aq") + "3NaOH(aq)"` `rarr` `"3NaI(aq) +Fe(OH)"_3darr"`

The down arrow means that the compound is a precipitate, which is an insoluble solid formed from two solutions.

So the reaction produces the precipitate iron(III) hydroxide.

Net ionic equation: includes only the ions that reacted and their product.

`"Fe"^(3+)("aq") + "3OH"^(-)("aq")"` `rarr` `"Fe(OH)"_3darr"`

We can tell whether an ionic compound is soluble in water by consulting solubility rules.