CHEM Unit 4

Which of the following is/are a reason that water is a desirable heat sink for use in calorimeters?

Consider a thermodynamic system that is si- multaneously releasing heat and doing work. The internal energy of this system will:

Which of the following statements is/are true? I) For a given process, ∆H must be zero when external pressure is zero. II) For a given process, ∆U and ∆H must have different values. III) For a given process, ∆Usys and ∆Usurr must have the same magnitude.

The formation of chemical bonds from sepa- rated atoms

? heat capacity is the amount of heat required to raise the temperature of one ? of an object by 1◦C. It is an ? product

The standard enthalpy of formation of Br2(l) is

in a closed system work is...

Which of the following will best help determine the direction of heat flow in a system?

If the products of a reaction have higher energy than the reactants, then the reaction...

Which of the following substances have ΔHf° = 0? Select all of the correct answers.

In order for an endothermic reaction to be spontaneous...

What are the values of ΔS for the water, the surroundings, and the universe for the evaporation of water from an open pan at 25°C?

True/False: For a given transfer of energy, a greater change in entropy occurs when the temperature is high.

H2 burning in O2 to form H2O (l) is an example of a system where the entropy of the universe decreases.

True/False: All entropies of fusion are negative.

A glass of cold water sits on a table top. As the day progresses, the water warms up to room temperature. For this process, ∆Ssurr is

The sublimation of solid carbon dioxide is a spontaneous process. Predict the sign (+, −, or 0) of ∆G◦r , ∆Hr◦, and ∆Sr◦, respectively.

At constant pressure and temperature, which of the following is true about ∆Ssurr

For a given reaction, if ∆H◦ rxn is (neg- is (nega- tive/positive/either), then the value of ∆G◦rxn will always be negative, regardless of the tem- perature.

The absolute entropy of a system (S mea- sured in J/K) is related to the number of microstates in that system. Consider the three processes listed below. Which one(s) will result in an increase in the number of microstates in the system?

The oxidation of sugar to carbon dioxide and water is a spontaneous chemical reac- tion. Since we know that reactions that occur spontaneously in one direction cannot occur spontaneously in the reverse direction, how can we understand photosynthesis?

The conditions for a specific exothermic re- action are such that it is currently non- spontaneous. Which of the following changes to the conditions will likely make the reaction spontaneous?

A particular protein folds spontaneously at 25 ◦C and 1 atm. During this folding, the pro- tein changes conformation from a higher en- tropy unfolded state to a lower entropy folded state. For this process, ∆H is

When water condenses, what are the signs for q, w, and ∆Ssys, respectively?

Which of the following is/are a reason that water is a desirable heat sink for use in calorimeters?

Consider a thermodynamic system that is si- multaneously releasing heat and doing work. The internal energy of this system will:

Which of the following statements is/are true? I) For a given process, ∆H must be zero when external pressure is zero. II) For a given process, ∆U and ∆H must have different values. III) For a given process, ∆Usys and ∆Usurr must have the same magnitude.

The formation of chemical bonds from sepa- rated atoms

The standard enthalpy of formation of Br2(l) is

You have two liquids of identical mass, and both with initial temperatures of 15◦C. One is ethanol, C2H5OH, with a specific heat of 2.46 J/g◦C and the other is benzene, C6H6, with a specific heat of 1.74 J/g◦C. If both liquids absorb the same amount of heat, which one will have the highest final temperature? Assume that neither liquid reaches its boiling point.

Which is true, considering the first law of thermodynamics?

Consider the following specific heats: copper, 0.384 J/g·◦C; lead, 0.159 J/g·◦C; water, 4.18 J/g·◦C; glass, 0.502 J/g·◦C. Which substance, once warmed, would be more likely to main- tain its heat and keep you warm through a long football game on a cold night?

Which statement about internal energy is true?

For an exothermic reaction, the sum of bond energies for the reactants are (greater/lesser) than those of the products.