Question

You need to prepare some calcium nitrate. (a) Write an intact-molecule balanced equation for an acid-base neutralization reaction that could be used to prepare calcium nitrate. (b) Write the net ionic equation for the neutralization.

Short answer

The balanced equation for the acid-base neutralization reaction between calcium hydroxide and nitric acid is: \(Ca(OH)_2 (s) + 2HNO_3 (aq) \rightarrow Ca(NO_3)_2 (aq) + 2H_2O (l)\) The net ionic equation for this neutralization reaction is: \(Ca(OH)_2 (s) + 2H^+ (aq) \rightarrow Ca^{2+} (aq) + 2H_2O (l)\)

Step-by-step solution

a) Balanced equation for an acid-base neutralization reaction

To prepare calcium nitrate, we can start with calcium hydroxide, a strong base, and nitric acid, a strong acid. The general reaction for an acid-base neutralization is: Acid + Base → Salt + Water Let's write the balanced equation for the reaction between calcium hydroxide and nitric acid: \(Ca(OH)_2 (s) + 2HNO_3 (aq) → Ca(NO_3)_2 (aq) + 2H_2O (l)\) Here, the calcium hydroxide (base) reacts with nitric acid (acid) to form calcium nitrate (salt) and water.

b) Net ionic equation for the neutralization

First, we need to identify the major species present in the solution before the reaction occurs, and their states: - Calcium hydroxide, \(Ca(OH)_2 (s)\): Solid, not dissolved in water. - Nitric acid, \(HNO_3 (aq)\): Strong acid, completely dissociated in water into ions: \(H^+ (aq)\) and \(NO_3^- (aq)\). Now, let's write the total ionic equation, which is the same as the balanced equation but with all the soluble ionic species dissociated into their respective ions: \(Ca(OH)_2 (s) + 2H^+ (aq) + 2NO_3^- (aq) → Ca^{2+} (aq) + 2NO_3^- (aq) + 2H_2O (l)\) Now, we can remove the spectator ions, which are the ions that do not participate in the reaction. In this case, the nitrate ions, \(NO_3^-\), are spectator ions because they appear on both sides of the equation in the same form. So, we can remove them from the total ionic equation: \(Ca(OH)_2 (s) + 2H^+ (aq) → Ca^{2+} (aq) + 2H_2O (l)\) This is the net ionic equation for the neutralization reaction, showing only the species that are participating in the reaction and changing forms.

Key concepts

Balanced Chemical Equation

The cornerstone of understanding any chemical reaction lies in the balanced chemical equation. It serves not only as a recipe for how compounds interact but also provides insights into the proportions in which they combine. In balanced chemical equations, the number of atoms for each element and the total charge are the same on both sides of the reaction. This principle is known as the Law of Conservation of Mass.

For instance, the balanced equation provided in the exercise for preparing calcium nitrate via neutralization involves a reaction between calcium hydroxide and nitric acid. The right proportion of reactants is crucial: one molecule of calcium hydroxide reacts with two molecules of nitric acid, resulting in one molecule of calcium nitrate and two molecules of water. The equation \[Ca(OH)_2 (s) + 2HNO_3 (aq) → Ca(NO_3)_2 (aq) + 2H_2O (l)\]is balanced because the number of each type of atom (calcium, oxygen, hydrogen, and nitrogen) remains constant before and after the reaction, adhering to the conservation principle.

Net Ionic Equation

To fully grasp the specifics of what happens in a solution during a chemical reaction, a closer look through the net ionic equation becomes necessary. This equation provides a more precise depiction by eliminating spectator ions that do not participate in the actual chemical change, thereby focusing on the essence of the reaction.

In the neutralization reaction to form calcium nitrate, once we have the complete ionic equation, recognizing the spectator ions is the key step. The ionic equation portrays every substance that ionizes in solution, showing us the true active participants. After the spectator ions, in this case the nitrate ions (\(NO_3^−\)), are removed, we are left with the core of the reaction:\[Ca(OH)_2 (s) + 2H^+ (aq) → Ca^{2+} (aq) + 2H_2O (l)\].The net ionic equation reveals the essence of the reaction – the transformation of calcium hydroxide and hydrogen ions into calcium ions and water.

Reaction Stoichiometry

The term 'stoichiometry' originates from the Greek words 'stoicheion' (element) and 'metron' (measure), aptly describing the aspect of chemistry that involves the measurement of elements within a reaction. It is the calculated relationship between the quantities of reactants and products in a chemical reaction, which is determined by the balanced chemical equation.

When studying the stoichiometry of the calcium nitrate preparation reaction, we notice that stoichiometry outlines that one mole of calcium hydroxide reacts with two moles of nitric acid to yield one mole of calcium nitrate and two moles of water. This quantitative relationship allows chemists to predict the amounts of reactants needed and products formed, making stoichiometry a fundamental concept for practical chemistry applications, including lab work and industrial production.

Understanding reaction stoichiometry is fundamental for students as it not only aids in predicting product yield but also ensures that no reactants are wasted, a concept pivotal in both economic and environmental contexts.