Problem 102 - Chemistry Matter and Change

Question

Paper A reaction occurs when sulfurous acid \(\left(\mathrm{H}_{2} \mathrm{SO}_{3}\right)\) is mixed with an aqueous solution of sodium hydroxide. The reaction produces aqueous sodium sulfite, a chemical used in manufacturing paper. Write the chemical and net ionic equations for the reaction.

Step-by-Step Solution

Answer

The balanced chemical equation for the reaction between sulfurous acid and sodium hydroxide is: 2\(\mathrm{H}_2\mathrm{SO}_3\) + 2\(\mathrm{NaOH}\) → \(\mathrm{Na}_2\mathrm{SO}_3\) + 2\(\mathrm{H}_2\mathrm{O}\). The net ionic equation for this reaction is: 2\(\mathrm{H^+}\) + 2\(\mathrm{OH^-}\) → 2\(\mathrm{H_2O}\).

Step 1: Write the unbalanced chemical equation

Write down the formulas of reactants and products for the given reaction: Sulfurous acid + Sodium hydroxide → Sodium sulfite + Water \(\mathrm{H}_2\mathrm{SO}_3\) + \(\mathrm{NaOH}\) → \(\mathrm{Na}_2\mathrm{SO}_3\) + \(\mathrm{H}_2\mathrm{O}\)

Step 2: Balance the chemical equation

Balance the chemical equation by making sure that the number of each type of atom on both sides of the equation is equal. 2\(\mathrm{H}_2\mathrm{SO}_3\) + 2\(\mathrm{NaOH}\) → \(\mathrm{Na}_2\mathrm{SO}_3\) + 2\(\mathrm{H}_2\mathrm{O}\)

Step 3: Write the complete ionic equation

Write down the complete ionic equation by showing all strong electrolytes in their ionic forms: 2\(\mathrm{H^+}\) + 2\(\mathrm{SO_3^{2-}}\) + 2\(\mathrm{Na^+}\) + 2\(\mathrm{OH^-}\) → 2\(\mathrm{Na^+}\) + \(\mathrm{SO_3^{2-}}\) + 2\(\mathrm{H_2O}\)

Step 4: Identify and remove spectator ions

Spectator ions are those ions that appear on both sides of the complete ionic equation and do not participate in the reaction. In this case, \(\mathrm{Na^+}\) and \(\mathrm{SO_3^{2-}}\) are the spectator ions. Remove the spectator ions from the complete ionic equation:

Step 5: Write the net ionic equation

Write the net ionic equation by including only those ions and molecules that are involved in the reaction: 2\(\mathrm{H^+}\) + 2\(\mathrm{OH^-}\) → 2\(\mathrm{H_2O}\) The net ionic equation for the reaction between sulfurous acid and sodium hydroxide is: 2\(\mathrm{H^+}\) + 2\(\mathrm{OH^-}\) → 2\(\mathrm{H_2O}\)

Key Concepts

Sulfurous Acid

Sulfurous acid, represented by the chemical formula \(\mathrm{H}_2\mathrm{SO}_3\), is an important chemical in many reactions. It is an unstable, weak acid formed when sulfur dioxide \( \mathrm{SO}_2 \) dissolves in water. While it is rarely found in pure form, it plays a crucial role in producing sulfites, which are useful in numerous applications, including as preservatives in the food and beverage industry. Sulfurous acid is characterized by its tendency to easily decompose into sulfur dioxide and water, making it an interesting subject of study in chemistry. Its reactivity is part of why it is useful in various chemical processes, like the reaction with sodium hydroxide described here.

Sodium Hydroxide

Sodium hydroxide, with the chemical formula \(\mathrm{NaOH}\), is a strong base used extensively in different chemical industries. Commonly known as lye or caustic soda, it is produced through the electrolysis of sodium chloride solution. Some key properties of sodium hydroxide include:

• Highly corrosive: It can cause severe burns upon contact with skin.
• Soluble in water: Dissolves easily, resulting in an exothermic reaction where heat is released.

Sodium hydroxide is widely used in the manufacture of paper, soap, and numerous chemical intermediates. In chemical reactions, it tends to dissociate into sodium ions \(\mathrm{Na^+}\) and hydroxide ions \(\mathrm{OH^-}\), which are effective reactants for neutralizing acids.

Net Ionic Equation

Net ionic equations are streamlined representations of a chemical reaction focusing only on the components directly involved in the reaction. Unlike full ionic equations, they exclude spectator ions, which are ions present on both sides of the reaction but do not participate. The process for creating a net ionic equation involves the following steps:

• Write out the complete ionic equation, showing all strong electrolytes as ions.
• Identify and remove spectator ions from the equation.
• Write the simplified version, including only the species that undergo a chemical change.

For the reaction between sulfurous acid \(\mathrm{H}_2\mathrm{SO}_3\) and sodium hydroxide \(\mathrm{NaOH} \), the net ionic equation is:\[2\mathrm{H^+} + 2\mathrm{OH^-} \rightarrow 2\mathrm{H_2O}\]This equation simplifies the interaction to focus on the formation of water from hydrogen and hydroxide ions.

Balancing Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is obeyed. This law states that matter cannot be created or destroyed in a chemical reaction. To balance an equation, ensure the number of atoms for each element is equal on both the reactant and product sides. This often involves adjusting coefficients of the molecules involved, rather than changing the chemical formulas themselves. Steps to balance an equation include:

• List each element and count the number of atoms present on both sides of the equation.
• Adjust the coefficients to balance each element one at a time.
• Check your work to ensure both sides are balanced.

In the reaction \(2\mathrm{H}_2\mathrm{SO}_3 + 2\mathrm{NaOH} \rightarrow \mathrm{Na}_2\mathrm{SO}_3 + 2\mathrm{H_2O}\), balancing ensures there is an equal number of each type of atom on both sides, maintaining the integrity of the reaction.