Question 1

Which of the following best describes a closed system as shown in the first two images?

Accepted Answer

A system that can exchange energy (as heat or work) but not matter with its surroundings.

Question 2

In the energy diagram for the reaction $$\mathrm{H_2$(g) + O_2$(g) \rightarrow H_2O(l)}$$, what does a negative $$\Delta E$$ indicate?

Accepted Answer

The system releases energy to the surroundings.

Question 3

A battery is fully charged and then used to power a motor, as shown in the last image. Which form(s) of energy are transferred from the battery to the motor?

Accepted Answer

Both heat and work are transferred.

Question 4

If a system absorbs 120 J of heat and does 40 J of work on the surroundings, what is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = 80\ \mathrm{J}$$

Question 5

Which scenario represents an endothermic process, as illustrated in the images?

Accepted Answer

Heat flows from the surroundings into the system, decreasing the temperature of the surroundings.

Question 6

A sample of water with a heat capacity of $$720\ \mathrm{J/\degree C} is $$heated from $$19.2\ \degree C to$$ $$23.5\ \degree C. $$How much heat ($$q) is $$absorbed?

Accepted Answer

$$q = 3,096\ \mathrm{J}$$

Question 7

Which of the following is NOT a state function?

Accepted Answer

Heat ($$q)$$

Question 8

A metal sample with mass $$32.91\ \mathrm{g}$$ absorbs $$235\ \mathrm{J} of $$heat, raising its temperature by $$2.53\ \degree C. $$What is its specific heat ($$C_s$$)?

Accepted Answer

$$C_s = 2.83\ \mathrm{J/g\degree C}$$

Question 9

Which of the following statements about specific heat is correct?

Accepted Answer

Specific heat is unique to each substance and is an intensive property.

Question 10

A sample of calcium carbonate ($$\mathrm{$$CaCO_3$$}) $$absorbs $$45.5\ \mathrm{J} of $$heat, increasing its temperature from $$21.1\ \degree C to$$ $$28.5\ \degree C. If $$the specific heat is $$0.82\ \mathrm{J/g\degree C}$$, what is the mass of the sample?

Accepted Answer

$$5.0\ \mathrm{g}$$

Question 11

Which of the following best describes an exothermic reaction, as shown in the images?

Accepted Answer

Heat flows from the system into the surroundings, increasing the temperature of the surroundings.

Question 12

Which equation correctly represents the relationship between internal energy, heat, and work?

Accepted Answer

$$\Delta E = q + w$$

Question 13

If a system loses 50 J of heat and has 30 J of work done on it by the surroundings, what is $$\Delta E$$?

Accepted Answer

$$\Delta E = -20\ \mathrm{J}$$

Question 14

Which of the following is a real-life example of an endothermic process?

Accepted Answer

Both ice melting and boiling soup

Question 15

Which property is path-independent and only depends on the current state of the system?

Accepted Answer

Internal energy ($$E)$$

Question 16

A chemical reaction occurs in a closed system and releases energy to the surroundings. Which sign convention is correct for $$\Delta E$$?

Accepted Answer

$$\Delta E \u003c 0$$

Question 17

Which of the following is true about heat capacity ($$C$$)?

Accepted Answer

It is an extensive property and depends on both sample size and substance identity.

Question 18

Which scenario would always result in an increase in the internal energy of a system?

Accepted Answer

The system gains heat and has work done on it by the surroundings.

Question 19

Which equation is used to calculate the heat absorbed by a sample using its specific heat?

Accepted Answer

$$q = C_s 	imes m 	imes \Delta T$$

Thermochemistry: Energy, Heat, and Work in Chemical Systems

Study Guide - Practice Questions

Study Guide - Flashcards