Question

Although the alkali metal halides can be prepared directly from the elements, the far less expensive industrial route is treatment of the carbonate or hydroxide with aqueous hydrohalic acid (HX) followed by recrystallization. Balance the reaction between potassium carbonate and aqueous hydriodic acid.

Short answer

The balanced equation is \( K_2CO_3 + 2HI \rightarrow 2KI + CO_2 + H_2O \).

Step-by-step solution

Identify the Reactants and Products

The reactants are potassium carbonate (\(K_2CO_3\)) and hydriodic acid (\(HI\)). The products will be potassium iodide (\(KI\)), carbon dioxide (\(CO_2\)), and water (\(H_2O\)).

Write the Unbalanced Equation

We begin by writing the chemical equation with the correct formulas:\[ K_2CO_3 + HI \rightarrow KI + CO_2 + H_2O \]

Balance Potassium (K) Atoms

There are 2 potassium (K) atoms in \(K_2CO_3\) and 1 in \(KI\). Therefore, we need 2 \(KI\):\[ K_2CO_3 + HI \rightarrow 2KI + CO_2 + H_2O \]

Balance Iodine (I) Atoms

We have 2 iodine (I) atoms in 2 \(KI\), so we need 2 \(HI\) to balance the iodine:\[ K_2CO_3 + 2HI \rightarrow 2KI + CO_2 + H_2O \]

Balance Hydrogen (H) and Oxygen (O) Atoms

Check the balance for hydrogen and oxygen atoms. On the product side, we have 1 \(H_2O\), which means 2 hydrogens (H) and 1 oxygen (O). Since the reactants already balance the oxygens (3 from \(CO_3\)) and hydrogens (2 from 2 \(HI\)), the equation is balanced.

Write the Balanced Equation

The final balanced equation is:\[ K_2CO_3 + 2HI \rightarrow 2KI + CO_2 + H_2O \]

Key concepts

Reactants

In a chemical reaction, 'reactants' are the starting substances that react with each other. They are the ingredients needed to start the chemical process. For example, in the exercise, the reactants are potassium carbonate \(K_2CO_3\) and hydriodic acid \(HI\).
Reactants always undergo a transformation during the reaction to become new substances called products. They are typically listed on the left side of the chemical equation.
Understanding the nature of reactants helps us predict the kind of reaction that will take place.

Products

'Products' are the substances that are formed as a result of the chemical reaction. They come from the transformation of reactants.
In our balancing exercise, the products are potassium iodide \(KI\), carbon dioxide \(CO_2\), and water \(H_2O\).
Products are shown on the right side of the chemical equation. Knowing the products of a chemical reaction allows us to understand the chemical changes that occurred and the result of the reaction.

Balanced Chemical Equation

A 'balanced chemical equation' ensures that the number of atoms for each element is the same on both sides of the equation. This is essential because the Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction.
To balance the provided exercise, we started with the unbalanced equation: \( K_2CO_3 + HI \rightarrow KI + CO_2 + H_2O \).
We then adjusted coefficients to ensure the same number of each type of atom appeared on both sides:

• Balanced potassium by adding a coefficient of 2 to \(KI\)
• Balanced iodine by adding a coefficient of 2 to \(HI\)
• Checked hydrogen and oxygen to confirm they balanced
• The final balanced equation is \( K_2CO_3 + 2HI \rightarrow 2KI + CO_2 + H_2O \).

This method helps in correctly describing the reaction.

Stoichiometry

'Stoichiometry' is the area of chemistry that involves calculating the quantities of reactants and products in a chemical reaction. It helps in understanding how much of a reactant is required or how much of a product will be formed.
In our example, stoichiometry helps us understand the ratio of reactants to products, such as 1 mole of potassium carbonate reacting with 2 moles of hydriodic acid to produce 2 moles of potassium iodide, 1 mole of carbon dioxide, and 1 mole of water.
This helps in practical applications, such as determining the quantities needed for industrial processes or laboratory experiments.