Question 1

Which of the following best describes the process shown in the first image, where $$\Delta H = -1367 kJ $$for the reaction $$\mathrm{C_2H_5OH(\ell) + 3O_2(g) \rightarrow 2CO_2(g) + 3H_2O(\ell)}$$?

Accepted Answer

The reaction is exothermic, releasing 1367 kJ of heat to the surroundings.

Question 2

A cyclist at the top of a hill (as shown in the second image) has high potential energy and zero kinetic energy. As the cyclist descends, what happens to the energies?

Accepted Answer

Potential energy decreases and kinetic energy increases.

Question 3

According to the third image, what happens to the electrostatic potential energy ($$E_{el}) as $$two like charges are brought closer together?

Accepted Answer

$$E_{el}$$ increases, indicating greater repulsion.

Question 4

In the fourth image, which best describes the system and surroundings for the reaction occurring inside the piston?

Accepted Answer

The system is the H$$_2(g) $$and O$$_2(g) $$inside the piston; the surroundings are the cylinder, piston, and everything beyond.

Question 5

A pot of water is heated on a burner as shown in the fifth image. Which statement is correct about the energy transfer?

Accepted Answer

Heat is transferred from the burner to the water, increasing the water's temperature.

Question 6

The sixth image shows a thermos. Which type of system does a thermos best approximate?

Accepted Answer

Isolated system

Question 7

Refer to the seventh image. If the internal energy of a system decreases, what does this indicate about the energy exchange?

Accepted Answer

The system has lost energy to the surroundings.

Question 8

In the eighth image, the reaction $$\mathrm{H_2$(g) + O_2$(g) \rightarrow H_2O(\ell)}$$ shows $$\Delta E \u003c 0. $$What does this mean?

Accepted Answer

The system releases energy to the surroundings.

Question 9

According to the sign conventions in the ninth image, which of the following is true if $$q is $$negative and $$w is $$positive?

Accepted Answer

The system loses heat and has work done on it.

Question 10

The tenth image shows the standard enthalpy of formation for CO$$_2(g). $$What is the value of $$\Delta H_f^\circ$$ for CO$$_2(g$$), and what does it represent?

Accepted Answer

$$\Delta H_f^\circ = -393.5 kJ/$$mol; it represents the heat released when one mole of CO$$_2 is $$formed from its elements in their standard states.

Question 11

Using the data in the twelfth and thirteenth images, what is the standard enthalpy of formation ($$\Delta H_f^\circ) $$for H$$_2(g$$)?

Accepted Answer

$$0 kJ/$$mol

Question 12

The fourteenth image shows the enthalpy change for the combustion of methane. If the reaction is reversed, what happens to the sign of $$\Delta H$$?

Accepted Answer

It becomes positive.

Question 13

According to the fifteenth image, which substance has the highest specific heat capacity at 298 K?

Accepted Answer

H$$_2O(l)$$

Question 14

The sixteenth image shows a bomb calorimeter. What is the main purpose of this device?

Accepted Answer

To measure the heat evolved in combustion reactions at constant volume.

Question 15

The seventeenth image shows a coffee-cup calorimeter. What type of calorimetry does this setup represent?

Accepted Answer

Constant-pressure calorimetry

Question 16

A reaction in a coffee-cup calorimeter causes the temperature of the solution to increase. What can you conclude about the reaction?

Accepted Answer

The reaction is exothermic.

Question 17

In a bomb calorimeter experiment, 2.00 g of a substance is combusted, causing the temperature of the calorimeter to rise by 3.00°C. If the heat capacity of the calorimeter is 10.0 kJ/°C, what is the heat released by the reaction?

Accepted Answer

$$q_{rxn} = -30.0 kJ$$

Question 18

Which of the following statements about state functions is correct?

Accepted Answer

The value of a state function depends only on the initial and final states.

Thermochemistry and Calorimetry: Study Notes for General Chemistry

Guida di studio - Domande di pratica

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