Question

In the United States over the past few decades, emissions of ammonia have dramatically increased, although less so in the east than in the west. a. Show with a chemical equation that ammonia dissolves in rain to form a basic solution. b. Write the neutralization reaction for rain that contains both ammonia and nitric acid. c. Ammonium sulfate also is found in rain. Write a chemical equation that demonstrates how it could have formed.

Short answer

a. Ammonia dissolves in rain: \( NH_3 + H_2O \rightarrow NH_4^+ + OH^- \). b. Neutralization: \( NH_3 + HNO_3 \rightarrow NH_4NO_3 \). c. Ammonium sulfate formation: \( 2NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4 \).

Step-by-step solution

Dissolution of ammonia

When ammonia (\( NH_3 \)) dissolves in water, it reacts with water to form ammonium ions (\( NH_4^+ \)) and hydroxide ions (\( OH^- \)), creating a basic solution. The equation representing this reaction is:\[ NH_3(g) + H_2O(l) \rightarrow NH_4^+(aq) + OH^-(aq) \]

Neutralization of nitric acid with ammonia

When ammonia in rain comes in contact with nitric acid (\( HNO_3 \)), a neutralization reaction occurs. Nitric acid reacts with ammonia to produce ammonium nitrate (\( NH_4NO_3 \)). The balanced equation for this reaction is:\[ NH_3(aq) + HNO_3(aq) \rightarrow NH_4NO_3(aq) \]

Formation of ammonium sulfate

Ammonium sulfate can form in rain through the reaction of ammonia with sulfuric acid (\( H_2SO_4 \)). When ammonia gas reacts with sulfuric acid, ammonium sulfate (\( (NH_4)_2SO_4 \)) is produced. The balanced chemical equation is:\[ 2NH_3(g) + H_2SO_4(aq) \rightarrow (NH_4)_2SO_4(aq) \]

Key concepts

Chemical Equations

Chemical equations show how substances transform in chemical reactions. They provide information about the reactants, the products, and the process of the reaction. In a chemical equation, reactants are written on the left, while the products are on the right, separated by an arrow indicating the direction of the reaction.
For example, when ammonia (\( NH_3 \)) dissolves in water, it forms ammonium ions (\( NH_4^+ \)) and hydroxide ions (\( OH^- \)). This can be expressed as:

• Reactants: \( NH_3 \) (ammonia gas) and \( H_2O \) (water)
• Products: \( NH_4^+ \) (ammonium ion) and \( OH^- \) (hydroxide ion)

Understanding chemical equations helps us predict the properties and behaviors of substances involved in reactions.

Neutralization Reactions

Neutralization reactions occur when an acid and a base react to form water and a salt. This chemical reaction generally results in a neutral solution if all reactants are in the right proportions. A practical example is the reaction between ammonia, which acts as a base, and nitric acid (\( HNO_3 \)).
In this neutralization, ammonia neutralizes nitric acid to form ammonium nitrate (\( NH_4NO_3 \)), a type of salt. The chemical equation for this reaction is:

• Ammonia: \( NH_3 \)
• Nitric Acid: \( HNO_3 \)
• Ammonium Nitrate: \( NH_4NO_3 \)

This type of reaction is fundamental in many environmental and industrial processes.

Ammonium Sulfate Formation

Ammonium sulfate is commonly found in rain due to its formation through a reaction involving ammonia.When ammonia reacts with sulfuric acid (\( H_2SO_4 \)), it forms ammonium sulfate (\( (NH_4)_2SO_4 \)).

• The balanced chemical equation is: \[ 2NH_3(g) + H_2SO_4(aq) \rightarrow (NH_4)_2SO_4(aq) \]
• This reaction explains one of the many ways ammonium sulfate can appear in natural environments.

It's important in industrial applications, and in environmental chemistry because it influences soil chemistry and atmospheric acidity.

Basic Solution

A basic solution forms when a substance increases the concentration of hydroxide ions (\( OH^- \)) in water. Ammonia is a common agent known for creating a basic solution.
When dissolved in water, ammonia (\( NH_3 \)) takes up a hydrogen ion from water, forming an ammonium ion (\( NH_4^+ \)) and a hydroxide ion (\( OH^- \)). The increase in \( OH^- \) ions makes the solution basic. Basic solutions are usually characterized by:

• Pleasant smell, often associated with cleaning products like ammonia
• Ability to turn red litmus paper to blue
• A pH greater than 7

Understanding how basic solutions form helps in grasping many natural and industrial processes.

Environmental Chemistry

Environmental chemistry is the study of chemical processes that occur in the environment. It covers the behavior of chemicals in natural settings, how they affect ecosystems, and how they can be managed or mitigated.
Ammonia emissions have increased, affecting both air and water quality.

• Ammonia impacts soil chemistry and can contribute to the formation of fine particulate matter in the atmosphere.
• In rain, ammonia can form compounds such as ammonium sulfate, influencing the acidity and composition of precipitation.
• Neutralization reactions like those with nitric acid reduce acidity but change water chemistry by forming new compounds.

Awareness and control of these processes are crucial for environmental conservation and sustainable resource management.