Problem 42 - Chemistry Matter and Change

Question

Mixing nitric acid (HNO \(_{3} )\) and aqueous ammonium hydroxide produces water and aqueous ammonium nitrate.

Step-by-Step Solution

Answer

The reaction between nitric acid (HNO3) and aqueous ammonium hydroxide (NH4OH) is a balanced acid-base neutralization reaction, represented by the equation: HNO3(aq) + NH4OH(aq) → H2O(l) + NH4NO3(aq). In this reaction, an H+ ion from nitric acid combines with an OH- ion from ammonium hydroxide to form water, while the remaining NH4+ and NO3- ions combine to form the salt ammonium nitrate.

Step 1: Write the balanced chemical equation for the reaction.

The reaction between nitric acid and aqueous ammonium hydroxide can be written as: HNO3(aq) + NH4OH(aq) → H2O(l) + NH4NO3(aq) Now, we need to balance this chemical equation. We can notice that the equation is already balanced, as there is one nitrogen atom, one oxygen atom, and four hydrogen atoms on both the reactants and products side. The balanced chemical equation is: HNO3(aq) + NH4OH(aq) → H2O(l) + NH4NO3(aq)

Step 2: Identify the type of reaction.

This reaction can be classified as an acid-base neutralization reaction. A neutralization reaction occurs when an acid reacts with a base to produce a salt and water. In this case, the acid is nitric acid (HNO3) and the base is aqueous ammonium hydroxide (NH4OH). The products formed are water (H2O) and aqueous ammonium nitrate (NH4NO3), which is a salt.

Step 3: Explain the reaction in terms of the displacement of ions.

In an acid-base neutralization reaction, a hydrogen ion (H+) from the acid combines with a hydroxide ion (OH-) from the base to form water (H2O). The remaining positive ion from the base (NH4+) and the negative ion from the acid (NO3-) combine to form a salt (NH4NO3). This process can be described as a displacement of ions. So, in the given reaction: H+ (from HNO3) + OH- (from NH4OH) → H2O NH4+ (from NH4OH) + NO3- (from HNO3) → NH4NO3 Therefore, mixing nitric acid with aqueous ammonium hydroxide produces water and aqueous ammonium nitrate through an acid-base neutralization reaction involving the displacement of ions.

Key Concepts

Balanced Chemical Equation

When dealing with chemical reactions, it's vital to represent the process with a balanced chemical equation. This equation shows how reactants transform into products. Each side of the equation must contain the same number of each type of atom to obey the law of conservation of mass.

In our example of mixing nitric acid (HNO₃) and ammonium hydroxide (NH₄OH), the reaction produces water (H₂O) and ammonium nitrate (NH₄NO₃). The initial equation is written as:

• Reactants: HNO₃(aq) + NH₄OH(aq)
• Products: H₂O(l) + NH₄NO₃(aq)

Since there is an equal number of nitrogen, oxygen, and hydrogen atoms on both sides, the equation is already balanced, making it simpler to understand and analyze the chemical process.

Ion Displacement

Ion displacement refers to the exchange of ions between the reacting substances during a chemical reaction. In acid-base neutralization, a special kind of ion displacement takes place.

Let's break it down:

• The hydrogen ion \(H^+\) from the acid \(HNO_3\) comes together with the hydroxide ion \(OH^-\) from the base \(NH_4OH\) to form water \(H_2O\).
• Meanwhile, the ammonium ion \(NH_4^+\) formed from the base combines with the nitrate ion \(NO_3^-\) from the acid to create ammonium nitrate \(NH_4NO_3\).

This step-wise movement of ions showcases how reactants transform into products while maintaining the integrity of charges, conserving both mass and charge.

Reaction Types

Chemical reactions can be classified into different types, helping scientists understand and predict the outcomes of these reactions.

In this instance, we classify the reaction as an acid-base neutralization. In such a reaction:

• It involves an acid (nitric acid - \(HNO_3\) in this case) and a base (aqueous ammonium hydroxide - \(NH_4OH\)).
• These substances react to produce water and a salt.

Recognizing this type of reaction helps in predicting the products when combining various acids and bases and allows for better understanding of their properties.
It also plays a significant role in fields like chemistry and environmental science.

Chemical Equations

A chemical equation is the symbolic representation of a chemical reaction. It includes the reactants and products, their physical states, and sometimes conditions like temperature or catalysts.

For example, the equation:

• \( \text{HNO}_3(aq) + \text{NH}_4\text{OH}(aq) \rightarrow \text{H}_2\text{O}(l) + \text{NH}_4\text{NO}_3(aq) \)

provides comprehensive yet concise information.

By showing the transformation from reactants to products, chemical equations help chemists communicate how matter interacts and changes without needing a lengthy description of the processes. Understanding chemical equations is essential for fields ranging from biochemistry to pharmaceuticals and helps in modeling various scientific phenomena.