High School Chemistry : Help with Entropy
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Example Questions
Example Question #12 : Thermochemistry And Energetics
Which of the following phases and states has the highest entropy?
Colloid
Gas
Liquid
Solid
Aqueous solution
Gas
Entropy is defined as the amount of disorder in a system and is favored in biological and chemical systems. Any system will prefer to have higher entropy, and spontaneous reactions will generally increase entropy in the system.
Gas particles move at higher velocity and with greater range than particles in liquids and solids. This contributes to their high level of entropy. Aqueous solutions gain entropy with the number of ions in solution, but do not reach the same level of entropy of gases. Colloids are homogenized mixtures, such as milk, and follow relatively the same principles as aqueous solutions.
Example Question #2 : Help With Entropy
Which of the following results in a decrease in entropy?
Breaking a mirror
Melting ice
Allowing a gas to diffuse
Building a road
Building a road
Entropy can be thought of as the tendency for a system to favor disorder. This means that the least ordered scenario in a system is typically favored by probability. Entropy increases when disorder is increased. Examples include an ice cube melting into a puddle, a gas diffusing all throughout a room, and a mirror shattering. Each of these either increases the energy of the system or results in the creation of multiple pieces/particles from a single object.
When building a road, materials are placed in an ordered, specific manner. This gives it a negative entropy.
Example Question #3 : Help With Entropy
For any chemical reaction __________.
the entropy change of the universe is greater than or equal to zero
the system experiences an increase in entropy
the universe loses entropy
the entropy of the surroundings must decrease
the entropy change of the universe is greater than or equal to zero
Any reaction can be thought of as taking place in a system, while the surroundings are the rest of the universe. It helps to remember that the entropy of the universe is constantly increasing. This means that the entropy change in the universe increases following every reaction. A system can have a decrease in entropy, as long as the entropy of the surroundings increases by a greater value.
Example Question #2 : Help With Entropy
Is a process more or less likely to occur as temperature increases when 
More likely because Gibbs free energy will increase
The answer cannot be determined without knowing the change in enthalpy
Less likely because Gibbs free energy will decrease
More likely because Gibbs free energy will decrease
Less likely because Gibbs free energy will increase
More likely because Gibbs free energy will decrease
Spontaneity, or the likelihood that a reaction will occur, is determined by Gibbs free energy. The equation for Gibbs free energy is:
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