Which of these processes are nonspontaneous? Are the...

Which of these processes are nonspontaneous? Are the nonspontaneous processes impossible?
a. a bike going up a hill
b. a meteor falling to Earth
c. obtaining hydrogen gas from liquid water
d. a ball rolling down a hill

Key Concepts

Gibbs Free Energy

Gibbs free energy is a thermodynamic potential that helps predict whether a process will occur spontaneously at constant temperature and pressure. A negative value of Gibbs free energy indicates that a process can proceed spontaneously, while a positive value indicates that the process is nonspontaneous and requires input of energy. This concept is essential for evaluating the energetic favorability of physical and chemical processes.

Nonspontaneous Process

A nonspontaneous process is one that does not occur under given conditions unless an external input of energy is provided. In thermodynamic terms, these processes have a positive Gibbs free energy change (?G > 0) and, by themselves, do not proceed in the forward direction because they are not energetically favorable. However, these processes are not impossible; they can proceed if energy is supplied or if they are coupled to other processes that are spontaneous.

Spontaneous Process

A spontaneous process is one that occurs naturally without the need for added energy from its surroundings. It is characterized by a decrease in the overall free energy of the system, meaning that the process has a negative Gibbs free energy change (?G < 0). Spontaneous processes happen because they are thermodynamically favorable under a given set of conditions, such as the release of energy or an increase in entropy.

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