Chemistry 15.1-15.2

Which of the following familiar processes is/are spontaneous? Select all that apply. A ball rolling down a hill Water decomposing to H2 and O2 at 25oC Water boiling at 0°C and 1 atm A teaspoon of table salt dissolving in 1 L of boiling water

A ball rolling down a hill A teaspoon of table salt dissolving in 1 L of boiling water

Two unknown reactions (A and B) are analyzed. It is found that reaction A is exothermic, while reaction B is endothermic. Which of these reactions is spontaneous? Multiple choice question. Reaction B is spontaneous because it is endothermic. Reaction A is spontaneous because it is exothermic. Spontaneity cannot be determined from the given information.

Correct Answer Spontaneity cannot be determined from the given information. Why the rest of them is not right? Reaction B is spontaneous because it is endothermic. Reason: We must also know how the entropy of the system changes to assess spontaneity. Spontaneity is determined by the sign of ΔG, and ΔG is a function of both ΔH and TΔS. Reaction A is spontaneous because it is exothermic. Reason: Exothermic reactions are often spontaneous, but not always. The freezing of water to form ice is an exothermic process, but the process is not spontaneous at all temperatures. Spontaneity is determined by the sign of ΔG, and ΔG is a function of both ΔH and TΔS. Spontaneity cannot be determined from the given information. Reason: Correct - we must also know how the entropy of the system changes to assess spontaneity. Spontaneity is determined by the sign of ΔG, and ΔG is a function of both ΔH and TΔS.

Which of the following types of energy are forms of motional energy? Select all that apply. Multiple select questions?. rotational mechanical thermal vibrational translational

Correct Answer rotational vibrational translational

Match each symbol in the equation S = k ln W correctly with its definition. Instructions S S drop zone empty. k k drops zone empty. ln ln drop zone empty. W

S entropy k Boltzmann constant ln natural logarithm W number of possible arrangements

Match each definition with the appropriate term. Instructions Spontaneous process Nonspontaneous process

Spontaneous process A process that does occur under a given set of conditions Nonspontaneous process A process that does not occur under a given set of conditions

What quantity is a measure of how spread out or dispersed a system's energy is? Motional energy. Entropy Enthalpy Gibbs free energy

THE CORRECT ANSWER IS ENTROPY Motional energy Reason: Motional energy includes translational, vibrational, and rotational energy. Enthalpy Reason: Enthalpy is a measure of the heat exchanged between the system and the surroundings. Gibbs free energy Reason: Gibbs free energy is the energy available to do work.

True or false: If a process occurs spontaneously in one direction under a certain set of conditions, it does not occur spontaneously in the opposite direction under the same conditions.

TRUE. If a process occurs spontaneously in one direction under a certain set of conditions, it is not possible for the process to also occur spontaneously in the opposite direction under the same set of conditions.

Which of the following statements correctly describe why the process depicted in the illustration is spontaneous? Select all that apply. (The change is occurring from left to right in the illustration, and the system remains at a constant temperature.) Multiple select questions. The process is spontaneous because it possesses a positive value for ΔH. The process is spontaneous because it possesses a negative value for ΔH. The process is spontaneous due to an increase in entropy. The process is spontaneous due to the dispersal of the system's energy over a larger volume.

The process is spontaneous due to an increase in entropy. The process is spontaneous due to the dispersal of the system's energy over a larger volume.

Match the different forms of motional energy of molecules with their descriptions? Translational Vibrational Rotational

Translational The entire molecule moves through space. Vibrational Atoms in the molecule move relative to one another. Rotational Atoms spin about an axis running through the center of mass of the molecule.

Select the statements that correctly describe the microstates of a system, W. Select all that apply. W = NX, where N is the number of particles and X is the number of cells they occupy. W is the number of energetically equivalent ways the particles of a system may be arranged. Increasing the temperature of a system will increase W. Entropy increases with the number of microstates.

W is the number of energetically equivalent ways the particles of a system may be arranged. Increasing the temperature of a system will increase W. Entropy increases with the number of microstates.

Which of the following changes are favored in a spontaneous process? An increase in entropy A decrease in entropy An overall increase in energy An overall decrease in energy

An increase in entropy An overall decrease in energy

True or false: The state with the largest number of possible arrangements has the greatest entropy.

Correct Answer True reason: True Reason: The most probable state is the one with the largest number of energetically equivalent possible arrangements: S = k ln W. False Reason: The most probable state is the one with the largest number of energetically equivalent possible arrangements: S = k ln W.

In order to assess the spontaneity of a chemical reaction or physical process both the change in? and? associated with the reaction or process must be known.

Enthalpy and entropy

The ? a system is a measure of the ways in which the energy of the system can be dispersed.

Entropy

Which of the following familiar processes is/are spontaneous under the conditions stated? Select all that apply. . Ice melting at -10°C Ice melting at room temperature Iron rusting at room temperature A ball rolling uphill

Ice melting at room temperature Iron rusting at room temperature

Which of the following familiar processes is/are spontaneous under the conditions stated? Select all that apply. Multiple select question. Ice melting at -10°C Iron rusting at room temperature Ice melting at room temperature A ball rolling uphill

Iron rusting at room temperature Ice melting at room temperature

Which of the following statements correctly reflect the relationship between the spontaneity of a reaction and the sign of ΔH? Select a All endothermic processes are nonspontaneous. The spontaneity of a process is easily determined from the sign of ΔH for the reaction. A negative value of ΔH favors spontaneity. A negative value of ΔH favors spontaneity but does not assure it.

The sign of ΔH alone is not sufficient evidence to determine the spontaneity of a process. A negative value of ΔH favors spontaneity.

Mathematically entropy is defined by the equation S = k ln W. W represents the number of possible arrangements, where mathematically W = XN. X ? represents the number of containing N ?.

cells molecules