Question

Write balanced molecular and net ionic equations for the reaction between nitric acid and calcium hydroxide.

Short answer

The balanced chemical equation is 2 HNO3 + Ca(OH)2 → Ca(NO3)2 + 2 H2O. The net ionic equation 2 H+ + 2 OH- → 2 H2O.

Step-by-step solution

Write the Reactants

Begin by writing the chemical formulas for the reactants on the left side of the equation. Nitric acid is represented by HNO3, and calcium hydroxide by Ca(OH)2.

Write the Products

After the reaction, the products are calcium nitrate (Ca(NO3)2) and water (H2O). Place these on the right side of the equation.

Balance the Equation

Balance the equation by adjusting the coefficients to ensure the same number of atoms of each element on both sides. The balanced molecular equation is: 2 HNO3 + Ca(OH)2 → Ca(NO3)2 + 2 H2O.

Write the Total Ionic Equation

Break all soluble strong electrolytes into their ions: 2 H+ + 2 NO3- + Ca2+ + 2 OH- → Ca2+ + 2 NO3- + 2 H2O.

Cancel Spectator Ions

Identify and cancel the spectator ions that appear unchanged on both sides of the total ionic equation. In this case, Ca2+ and NO3- are spectator ions.

Write the Net Ionic Equation

Write the net ionic equation by removing the spectator ions from the total ionic equation, leaving only the species that undergo a chemical change: 2 H+ + 2 OH- → 2 H2O.

Key concepts

Chemical Reactions

A chemical reaction is a process where substances, called reactants, transform into different substances, known as products. This process involves the breaking and forming of chemical bonds, resulting in a change of the properties and composition of the substances.

For example, when nitric acid reacts with calcium hydroxide, a chemical reaction takes place. The reactants are nitric acid (HNO3) and calcium hydroxide (Ca(OH)2), and the products of this reaction are calcium nitrate (Ca(NO3)2) and water (H2O). During the reaction, the hydrogen ions (H+) from nitric acid combine with hydroxide ions (OH-) from calcium hydroxide to form water, illustrating the concept of a chemical reaction through the transformation of reactants into products.

Balanced Molecular Equation

A balanced molecular equation is critical in properly representing a chemical reaction. It shows the chemical formulas of the reactants and products with coefficients adjusted so that the number of atoms for each element is the same on both sides of the equation.

To achieve a balanced equation, start with the molecular form of the reactants and products, and then adjust the coefficients to balance the atoms. In the reaction between nitric acid and calcium hydroxide, the balanced molecular equation is 2 HNO3 + Ca(OH)2 → Ca(NO3)2 + 2 H2O. This equation reflects the stoichiometry of the reaction—two nitric acid molecules react with one calcium hydroxide molecule to produce one calcium nitrate molecule and two water molecules. Balancing equations ensures the conservation of mass, a foundational law in chemistry, is upheld.

Spectator Ions

In the context of ionic reactions, spectator ions are ions that do not take part in the actual chemical change but are present in the solution. They are called spectators because they are unchanged and appear on both the reactant and product side of the equation.

When writing the total ionic equation, all the strong electrolytes are separated into their ions, as seen in the reaction between nitric acid and calcium hydroxide. The equation before the removal of spectator ions is 2 H+ + 2 NO3- + Ca2+ + 2 OH- → Ca2+ + 2 NO3- + 2 H2O. From this, we observe that the calcium (Ca^2+) and nitrate ions (NO3-) are present on both sides, indicating they do not participate in the reaction. Hence, they are eliminated to form the net ionic equation which shows only the ions that actually change during the reaction. In this example, the net ionic equation is 2 H+ + 2 OH- → 2 H2O. Understanding spectator ions is essential for simplifying equations and focusing on the substances that are involved in the reaction.