Question

A student writes the following incorrect chemical equation for a double replacement reaction between iron(III) bromide and sodium hydroxide solutions.

FeBr₃(aq) + NaOH(aq) FeOH(s) + NaBr₃, (aq)
a. What is wrong with the chemical formula(s) of the product(s) predicted by this student? -> b. Write the correct equation for the double replacement reaction between iron(III) bromide and sodium hydroxide.

Answer 1

The student's incorrect formula for the products of the reaction between iron(III) bromide and sodium hydroxide are corrected by writing the balanced chemical equation FeBr3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaBr(aq), with the insoluble iron(III) hydroxide precipitating out of the solution.

Step-by-step explanation:

The incorrect chemical formula predicted by the student for the double replacement reaction between iron(III) bromide and sodium hydroxide is FeOH(s) and NaBr3, (aq). The correct products should maintain the oxidation states of the cations and the charge balance. Iron(III) has a +3 charge and would react with three hydroxide ions to form iron(III) hydroxide, not FeOH. Sodium has a +1 charge and would form a 1:1 compound with bromide, not NaBr3.

The proper chemical equation for the double replacement reaction between iron(III) bromide (FeBr3) and sodium hydroxide (NaOH) is:

FeBr3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaBr(aq)

Iron(III) hydroxide is insoluble and will form a precipitate, whereas sodium bromide is soluble and will remain in solution.