Q: Which of the following is the correct formula for calculating heat ($$q) $$when the temperature of a substance changes?

$$q = m \times C \times \Delta T$$

Question 1

Which statement best describes the First Law of Thermodynamics?

Accepted Answer

The total energy of the universe is constant; energy can be transferred but not created or destroyed.

Question 2

A chemical reaction occurs in a closed container. The internal energy of the reactants is higher than that of the products. What is the sign of $$\Delta E_{sys}$$ and what does it mean?

Accepted Answer

$$\Delta E_{sys} is $$negative; energy flows out of the system into the surroundings.

Question 3

Which of the following is the correct formula for calculating heat ($$q) $$when the temperature of a substance changes?

Accepted Answer

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

Question 4

A 50.0 g aluminum block initially at 25.0 $$^\circC $$absorbs 725 J of heat. What is its final temperature? (Specific heat capacity of Al = 0.900 J/g$$^\circC)$$

Accepted Answer

40.1 $$^\circC$$

Question 5

Which of the following best defines 'specific heat capacity'?

Accepted Answer

The amount of heat required to raise the temperature of 1 gram of a substance by 1 $$^\circC.$$

Question 6

During a chemical reaction in a hand warmer, heat is released to the surroundings. How is this process classified?

Accepted Answer

Exothermic; the system releases heat to the surroundings.

Question 7

Which of the following is NOT considered part of the 'system' in thermochemistry?

Accepted Answer

The air outside the reaction vessel.

Question 8

If a system does work on the surroundings and loses heat, what is the sign of $$q$$ and $$w$$?

Accepted Answer

$$q is $$negative, $$w is $$negative.

Question 9

Which equation correctly relates the change in internal energy ($$\Delta E) to $$heat and work?

Accepted Answer

$$\Delta E = q + w$$

Question 10

A student mixes two solutions in a calorimeter and observes the temperature increases. What does this indicate about the direction of heat flow?

Accepted Answer

Heat flows from the surroundings to the system.

Question 11

Which of the following statements about state functions is correct?

Accepted Answer

State functions depend only on the initial and final states, not on the path taken.

Question 12

Which unit is larger: calorie or joule? (Given: $$1 	ext{ cal} = 4.184 	ext{ J})$$

Accepted Answer

Calorie is larger than joule.

Question 13

A metal block at 80.0 $$^\circC is $$placed in water at 25.0 $$^\circC. $$What is the final temperature when thermal equilibrium is reached?

Accepted Answer

Between 25.0 $$^\circC $$and 80.0 $$^\circC$$

Question 14

Which of the following best describes 'thermal equilibrium'?

Accepted Answer

When two objects reach the same temperature and no net heat flows between them.

Question 15

In the reaction $$\mathrm{C(s) + O_2$(g) \rightarrow CO_2$(g)}$$, which statement is true regarding the internal energy change?

Accepted Answer

The internal energy change is the difference between the energy of the products and the reactants.

Question 16

A student stirs a hot beverage and notices it cools down over time. Which process is responsible for the temperature decrease?

Accepted Answer

Heat flows from the beverage to the surroundings.

Question 17

Which of the following is a correct statement about energy transfer in a system?

Accepted Answer

Energy can be transferred as heat or work between the system and surroundings.

Question 18

If the surroundings do work on the system, what is the sign of $$w$$ for the system?

Accepted Answer

$$w is $$positive.

Question 19

Which of the following scenarios best illustrates the concept of energy conservation?

Accepted Answer

A chemical reaction releases heat, which is absorbed by the surroundings.

Thermochemistry: Energy, Heat, and Work in Chemical Systems

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