18.1.1 Spontaneous Processes

Question 1

Spontaneous Processes

Answer 1

• The spontaneity of a process is independent of the time it takes for the process to occur.
• The reverse of a spontaneous process will not be spontaneous.
• Some processes are spontaneous without being energy-driven; these processes are driven by an increase in disorder.

Question 2

note

Answer 2

• In chemistry, a spontaneous process is a process that occurs without outside assistance.
• The spontaneity of a process is independent of the time it takes for the process to occur.
• For example, the rate at which honey flows from a bottle, sap moves through a tree, or a rock falls down a mountain does not determine whether or not the processes are spontaneous.
• The three events occur at different rates, yet are all considered to be spontaneous processes.
  The reverse of a spontaneous process will not be spontaneous.
• Energy differences, as found when a chemical reaction proceeds from a high to a low energy state, often cause a process to be spontaneous. For example, butane combustion is a spontaneous process. The reaction proceeds from butane and oxygen (high-energy molecules) to carbon dioxide and water (lower energy molecules). The formation of butane from carbon dioxide and water is not spontaneous.
• Some processes are spontaneous without being
  energy-driven; these processes are driven by an increase in disorder.
• In a spontaneous process, the gas inside the balloon explodes out, but is not expected to rush back into the balloon as a spontaneous process. A change in energy states is not the reason for the spontaneity of the process. This is one example of disorder-driven spontaneity; a spontaneous process that increases the disorder of the system

Question 3

Which statement about spontaneous events is not correct?

Answer 3

All spontaneous events occur because of a system’s desire to minimize its potential energy.

Question 4

Which of the following is not a potential cause for a spontaneous reaction?

Answer 4

the rate of a reaction or process

Question 5

Which of the following events involves a spontaneous reaction that does not include a change in energy?

Answer 5

releasing a gas into the atmosphere

Question 6

Which of the following spontaneous events is not explained correctly?

Answer 6

Marbles dispersing in a tray is an example of a spontaneous event that is exclusively driven by gravity.

Question 7

Which of the following is a nonspontaneous event?

Answer 7

a wheelbarrow being moved from one place to another

Question 8

Which statement about a spontaneous process is not true?

Answer 8

When energy is used to propel an event (such as a chemical reaction), the event cannot be considered spontaneous.

Question 9

Look at the curve for the reaction of butane and oxygen (with heat) to form CO2 and H2O.

Which statement best explains why the forward reaction (i.e., butane and oxygen (with heat) combine to form CO2 and H2O) is considered spontaneous?

Answer 9

When butane and oxygen are heated, they readily and naturally convert to CO2 and H2O, minimizing their potential energy in the process.

Question 10

Recall the demonstration in which a group of marbles was released onto a tray and subsequently shaken. Which statement about this event is not correct?

Answer 10

This process (or event) cannot be reversed.

Question 11

Look at the butane and oxygen reaction.

Which statement about this reaction is not correct?

Answer 11

Because the forward reaction is spontaneous, there is no energy demand for this reaction to proceed.

Question 12

Which of the following examples of a spontaneous reaction does not involve a chemical energy difference?

Answer 12

a glider (plane) landing on an airport runway