Question

Write the balanced chemical equation for the reaction of aqueous potassium hydroxide with aqueous iron(III) chloride to form solid iron(III) hydroxide and aqueous potassium chloride.

Short answer

The balanced chemical equation for the reaction of aqueous potassium hydroxide with aqueous iron(III) chloride is \( 3KOH_{(aq)} + FeCl_3_{(aq)} \rightarrow Fe(OH)_3_{(s)} + 3KCl_{(aq)} \).

Step-by-step solution

Write the Unbalanced Equation

Begin by writing the formulas for the reactants (potassium hydroxide and iron(III) chloride) and the products (iron(III) hydroxide and potassium chloride). The unbalanced chemical equation is: \( KOH_{(aq)} + FeCl_3_{(aq)} \rightarrow Fe(OH)_3_{(s)} + KCl_{(aq)} \).

Balance the Iron Atoms

Start balancing the atoms one type at a time. There is one iron atom on each side of the equation, so iron is already balanced.

Balance the Chlorine Atoms

There are three chlorine atoms on the left side and only one chlorine atom on the right. To balance chlorine, put a coefficient of 3 in front of \( KCl \): \( KOH_{(aq)} + FeCl_3_{(aq)} \rightarrow Fe(OH)_3_{(s)} + 3KCl_{(aq)} \).

Balance the Potassium Atoms

With the chlorine atoms balanced, now balance the potassium atoms. There is one potassium atom in potassium hydroxide and three in potassium chloride on the right side. To balance, put a coefficient of 3 in front of \( KOH \): \( 3KOH_{(aq)} + FeCl_3_{(aq)} \rightarrow Fe(OH)_3_{(s)} + 3KCl_{(aq)} \).

Balance the Hydrogen Atoms

Now look at the hydrogens. There are three hydroxide groups on the left with a total of three hydrogen atoms, which matches the three hydroxide groups in the iron(III) hydroxide on the right.

Balance the Oxygen Atoms

There are three oxygen atoms in the three hydroxide ions on the left and three oxygen atoms in the iron(III) hydroxide on the right side. Oxygen is therefore balanced.

Write the Balanced Chemical Equation

Now that all the elements are balanced, we can write the final balanced chemical equation: \( 3KOH_{(aq)} + FeCl_3_{(aq)} \rightarrow Fe(OH)_3_{(s)} + 3KCl_{(aq)} \).

Key concepts

Chemical Reaction

A chemical reaction involves the transformation of one or more substances, known as reactants, into one or more different substances, called products. During this process, chemical bonds are broken and formed, leading to a change in the composition and properties of the matter involved.
For example, when aqueous potassium hydroxide reacts with aqueous iron(III) chloride, a new substance, solid iron(III) hydroxide, and aqueous potassium chloride are formed. This reaction demonstrates the conversion of reactants into products through a chemical process.

Stoichiometry

Stoichiometry is the calculation of the quantities of reactants and products in chemical reactions. It's based on the conservation of mass and the concept of moles, which allows chemists to predict the amounts of substances consumed and produced in a given reaction.
When balancing the reaction between potassium hydroxide and iron(III) chloride, stoichiometry is used to determine the correct ratio of potassium hydroxide to iron(III) chloride needed to form iron(III) hydroxide and potassium chloride without any excess reactants.

Balancing Equations

Balancing chemical equations is a fundamental skill in chemistry, ensuring that the number of atoms for each element is the same on both sides of the equation, as per the Law of Conservation of Mass. This process requires adding appropriate coefficients before the chemical formulas to achieve a balanced equation.
The balanced equation for the reaction between potassium hydroxide and iron(III) chloride shows the proper stoichiometric coefficients (3:1:1:3) to reflect the exact amounts of reactants and products involved.

Aqueous Solutions

Aqueous solutions are mixtures in which the solvent is water. In these solutions, substances (solutes) such as salts, acids, or bases are dissolved in water to form a homogeneous mixture.
Both potassium hydroxide and iron(III) chloride are solutes that dissolve in water to form aqueous solutions before reacting. The solubility of these compounds in water is a key factor for the reaction to occur.

Precipitation Reactions

Precipitation reactions occur when two aqueous solutions react and form an insoluble solid, known as a precipitate. During the reaction, the ions in the solution combine to form a compound that is not soluble in water.
In this example, the reaction between aqueous potassium hydroxide and aqueous iron(III) chloride produces solid iron(III) hydroxide, the precipitate. Recognizing the formation of the solid in the balanced equation is crucial in understanding precipitation reactions.