Question

1. according to the zeroth law of thermodynamics (teks 13a), if object a is in thermal equilibrium with object b, and object b is in thermal equilibrium with object c, then

a. a and c must be at different temperatures.
b. a and c must be in thermal equilibrium.
c. b must be warmer than a.
d. c must be cooler than a.

1. in a constant - pressure calorimeter, the heat flow into the system is measured and gives a negative q value. this indicates:

a. the system absorbed heat from surroundings.
b. the system released heat to surroundings.
c. no heat exchange took place.
d. the experiment was conducted incorrectly.

1. which of the following best describes why reaction rate and heat flow are separate concerns under teks 13d?

a. rate concerns how fast, while heat flow concerns how much energy is absorbed or released.
b. both rate and heat flow always increase together.
c. heat flow determines the rate of reaction.
d. rate only applies to gases, heat flow only to solids.

1. a chemical reaction in which the bonds formed in the products are stronger (and lower energy) than the bonds broken in the reactants is likely to be:

a. endothermic because net energy is absorbed.
b. exothermic because net energy is released.
c. endothermic because net energy is released.
d. exothermic because net energy is absorbed.

1. a sample of cold metal is dropped into warmer water in a calorimeter and the final temperature of the mixture is measured. which assumption must you make for accurate calculation under teks 13b and 13d?

a. the calorimeter absorbs no heat.
b. the pressure varies significantly.
c. the metal and water exchange electrons.
d. the water mass is negligible.

Explanation:

• Question 10: According to the zeroth law of thermodynamics, if \(A\) is in thermal equilibrium with \(B\) and \(B\) is in thermal equilibrium with \(C\), then \(A\) and \(C\) must be in thermal equilibrium (same temperature).
• Question 11: In a constant - pressure calorimeter, \(q=\Delta H\). A negative \(q\) value means the system released heat to the surroundings (\(q_{system}=-q_{surroundings}\)).
• Question 12: Rate of a reaction (e.g., in \(M/s\)) is about how fast reactants convert to products. Heat flow (\(q\) or \(\Delta H\)) is about the energy (absorbed or released) during the reaction.
• Question 13: If bonds formed in products are stronger (lower energy) than bonds broken in reactants, energy is released. An exothermic reaction has \(\Delta H<0\) (net energy released).
• Question 14: For calorimetry calculations (\(q_{metal}=-q_{water}\)), we assume that the calorimeter absorbs no heat. If it did, our calculation of \(q_{metal}\) and \(q_{water}\) based on \(q = mc\Delta T\) for water (and metal) would be incorrect.

Answer:

1. B. \(A\) and \(C\) must be in thermal equilibrium.
2. B. The system released heat to surroundings.
3. A. Rate concerns how fast, while heat flow concerns how much energy is absorbed or released.
4. B. Exothermic because net energy is released.
5. A. The calorimeter absorbs no heat.