Question

Which of the following processes are spontaneous, and \(\quad\) and \(1 \mathrm{~atm}\), (d) lightning, (e) formation of \(\mathrm{CH}_{4}\) and \(\mathrm{O}_{2}\) which are nonspontaneous: (a) the ripening of a banana, molecules from \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) at room temperature and (b) dissolution of sugar in a cup of hot coffee, (c) the re- 1 atm of pressure? action of nitrogen atoms to form \(\mathrm{N}_{2}\) molecules at \(25^{\circ} \mathrm{C}\)

Short answer

The spontaneous processes are: (a) the ripening of a banana, (b) dissolution of sugar in a cup of hot coffee, and (d) lightning. The nonspontaneous processes are: (c) the reaction of nitrogen atoms to form \(N_2\) molecules at \(25^{\circ}C\) and 1 atm of pressure, and (e) formation of \(CH_4\) and \(O_2\) molecules from \(CO_2\) and \(H_2O\) at room temperature and 1 atm pressure.

Step-by-step solution

(a) The ripening of a banana

Ripening of a banana is a natural process that occurs over time, without the need for any external influence once it starts. This is an example of a spontaneous process.

(b) Dissolution of sugar in a cup of hot coffee

The dissolution of sugar in a cup of hot coffee occurs naturally when sugar is added to the coffee. The sugar dissolves spontaneously, without the need for any continuous external influence. This is an example of a spontaneous process.

(c) The reaction of nitrogen atoms to form N2 molecules at 25°C and 1 atm of pressure

The reaction of nitrogen atoms to form N2 molecules at 25°C and 1 atm of pressure is not spontaneous, as nitrogen atoms do not naturally combine to form N2 molecules under these conditions. This process requires some external influence to occur (for example, high pressure or high temperature), so it is nonspontaneous.

(d) Lightning

Lightning takes place spontaneously as the result of a natural charge separation between clouds and the ground. The electrical discharge occurs without any external influence once it starts. Therefore, lightning is a spontaneous process.

(e) Formation of CH4 and O2 molecules from CO2 and H2O at room temperature and 1 atm pressure

The formation of CH4 and O2 molecules from CO2 and H2O at room temperature and 1 atm pressure is not a natural process. This reaction requires external influence or energy input, such as through a chemical reaction or photosynthesis. Hence, this is a nonspontaneous process.

Key concepts

Thermodynamics

Thermodynamics is a fundamental branch of physical science that explains energy and its transformations. It helps us understand whether a chemical process will occur spontaneously or will need an extra push from outside forces.
A key idea in thermodynamics related to spontaneity is the change in Gibbs free energy (\(\Delta G\)). A reaction is considered spontaneous if \(\Delta G\) is less than zero. On the contrary, for nonspontaneous reactions, \(\Delta G\) is greater than zero.
In simple terms:

• Spontaneous: Energy is released and the process happens naturally.
• Nonspontaneous: Energy must be added for the process to occur.

This principle helps us predict whether sugar will dissolve in coffee on its own or if energy is needed to combine nitrogen atoms at room temperature.

Chemical Reactions

Chemical reactions involve changes in substances through breaking and forming bonds between atoms. Whether these reactions occur on their own depends on various factors, including temperature and pressure.
For example, the ripening of bananas and the dissolution of sugar in coffee are processes where chemical transformations proceed without external energy. These are considered spontaneous as they result from internal conditions such as existing potential energy or entropy changes.
In contrast, forming molecules like methane (\(CH_4\)) from carbon dioxide and water at room temperature does not happen spontaneously. This is because the reactants need extra energy or the right catalysts to encourage the transformation. As a result, predicting spontaneity in chemical reactions involves understanding the required conditions for a reaction to occur.

Nonspontaneous Processes

Nonspontaneous processes are those that require additional energy to occur. Unlike their spontaneous counterparts, they do not happen naturally on their own.
A prime example is the reaction of nitrogen atoms to form \(N_2\) molecules at room temperature. This chemical process is nonspontaneous and requires specific conditions like high temperatures or pressures to proceed.
Nonspontaneous reactions are also significant in industrial and biological settings, where careful control of energy, temperature, and pressure leads to desired chemical transformations that do not occur under normal conditions.
In summary:

• Nonspontaneous: Needs energy input.
• Careful control is required to achieve the reaction.

Natural Phenomena

Natural phenomena are events that happen in nature without human intervention. They can range from simple processes like banana ripening to grand displays like lightning storms.
Lightning, for instance, is a striking natural occurrence that involves electrical discharges between clouds or from clouds to the ground. It happens spontaneously due to natural charge separations in the atmosphere, showcasing nature's spontaneity at work.
Similarly, the ripening of fruits, such as bananas, is a spontaneous natural process driven by internal changes in the fruit's chemistry. Unlike some agricultural techniques that may speed up or slow down this process, under natural conditions, it happens automatically without external aid.
These examples illustrate how spontaneous processes are often a hallmark of natural systems, reflecting a balance of energy and matter in the environment.