Q: A sample of water is heated from 20.0°C to 36.0°C. If the mass of water is 250 g and the specific heat capacity is $$4.18 \ \mathrm{J} \ \mathrm{g}^{-1} \ \mathrm{K}^{-1}$$, how much heat was transferred to the water?

$$q = 250 \times 4.18 \times 16 = 16,720 \ \mathrm{J}$$

Question 1

Which of the following best describes a spontaneous process in chemical thermodynamics?

Accepted Answer

A process that occurs without any input of energy from the surroundings under given conditions.

Question 2

Which equation correctly represents the first law of thermodynamics for a closed system?

Accepted Answer

$$\Delta U = q + w$$

Question 3

A sample of water is heated from 20.0°C to 36.0°C. If the mass of water is 250 g and the specific heat capacity is $$4.18 \ \mathrm{J} \ \mathrm{g}^{-1} \ \mathrm{K}^{-1}$$, how much heat was transferred to the water?

Accepted Answer

$$q = 250 	imes 4.18 	imes 16 = 16,720 \ \mathrm{J}$$

Question 4

Which of the following statements about heat capacity is correct?

Accepted Answer

Heat capacity is an extensive property and depends on the amount of substance.

Question 5

Which formula is used to calculate the change in temperature when a known amount of heat is added to a substance?

Accepted Answer

$$\Delta T = \frac{q}{mC}$$

Question 6

In a bomb calorimeter experiment, which equation is used to determine the heat released by the reaction?

Accepted Answer

$$q_{reaction} = -C_{cal} \Delta T$$

Question 7

Which of the following is true about enthalpy ($$\Delta H) $$under constant pressure?

Accepted Answer

$$\Delta H is $$equal to the heat absorbed or released by the system.

Question 8

Which equation represents Hess's Law for calculating the enthalpy change of a reaction?

Accepted Answer

$$\Delta H_{reaction} = \sum \Delta H_{products} - \sum \Delta H_{reactants}$$

Question 9

Which of the following factors increases the entropy ($$S) of a $$system?

Accepted Answer

Changing the physical state from solid to liquid.

Question 10

Which equation is used to calculate the entropy change ($$\Delta S) $$for a chemical reaction?

Accepted Answer

$$\Delta S = \sum S_{products} - \sum S_{reactants}$$

Question 11

A reaction has $$\Delta H = -100 \ \mathrm{kJ}$$ and $$\Delta S = 200 \ \mathrm{J} \ \mathrm{K}^{-1}. At $$what temperature will the reaction become non-spontaneous?

Accepted Answer

$$T \u003e 500 \ \mathrm{K}$$

Question 12

Which of the following is the correct definition of standard enthalpy of formation ($$\Delta H_f^\circ$$)?

Accepted Answer

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states at 298 K and 1 atm.

Question 13

Which of the following reactions would have the greatest increase in entropy?

Accepted Answer

$$CaCO_3(s$$) \rightarrow CaO(s) + $$CO_2(g$$)$$

Question 14

Which of the following is the correct expression for calculating the enthalpy change of a reaction using bond enthalpies?

Accepted Answer

$$\Delta H = \sum 	ext{Bond enthalpies of bonds broken} - \sum 	ext{Bond enthalpies of bonds formed}$$

Question 15

Which of the following statements about the universe, system, and surroundings is correct in thermodynamics?

Accepted Answer

The surroundings are everything outside the system.

Question 16

Which of the following is an example of an extensive property?

Accepted Answer

Volume

Question 17

Which equation is used to calculate the work done by a system during expansion at constant pressure?

Accepted Answer

$$w = -P_{ext} \Delta V$$

Question 18

Which of the following best explains why entropy increases with temperature?

Accepted Answer

Higher temperature means molecules move faster, increasing the number of possible arrangements.

Question 19

Which of the following is the correct formula for calculating the standard enthalpy change of a reaction using standard enthalpies of formation?

Accepted Answer

$$\Delta H_{reaction}^\circ = \sum \Delta H_f^\circ (	ext{products}) - \sum \Delta H_f^\circ (	ext{reactants})$$

Chemical Thermodynamics and Entropy: Core Concepts and Applications

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