Book: Ch. 6

Question 1

Define: thermodynamics

Answer 1

Study of energy and its transformations.

Question 2

Define: thermochemistry

Answer 2

Branch of thermodynamics that deals with heat in chemical and physical change.

Question 3

Define: system vs. surroundings [in thermodynamics]

Answer 3

System: the part of the universe we are focusing on.
Surroundings: everything else.

Question 4

Define: internal energy (E) of a system

Answer 4

The sum of all the energies of all the components of a system.

Question 5

What is the equation for change in the internal energy of a system?

Answer 5

∆E = E_final - E_initial = E_products - E_reactants

Question 6

Define: heat (q)

Answer 6

Thermal energy. The energy transferred as a result of a difference in temperature between the system and the surroundings.

Question 7

What is the equation for the total change in a system’s internal energy in terms of q and w?

Answer 7

∆E = q + w

Question 8

Define: law of conservation of energy (first law of thermodynamics)

Answer 8

∆E_universe = ∆E_sys + ∆E_surroundings = 0

Question 9

Define: joule (J)

Answer 9

SI unit of energy. 1 J = 1 kg m²/s²

Question 10

Define: calorie (cal)

Answer 10

1 cal = 4.184 J

Question 11

Define: state function

Answer 11

A property dependent only on the current state of the system, not on the path the system takes to reach that state. Examples: internal energy, composition, pressure, volume, temperature.

Question 12

Define: pressure-volume work (PV work)

Answer 12

A type of mechanical work done when the volume of the system changes in the presence of an external pressure: w = -P∆V

Question 13

Define: enthalpy (H)

Answer 13

For reactions at constant pressure, enthalpy eliminates the need to deal with PV work. H = E + PV

Question 14

Define: change in enthalpy (∆H)

Answer 14

Change in the system’s internal energy plus the product of the pressure and the change in volume: ∆H = ∆E + P∆V

Question 15

How is ∆H related to heat?

Answer 15

∆H = q_p, or enthalpy equals the heat absorbed or released at constant pressure.

Question 16

Define: exothermic process

Answer 16

Releases heat as a product. Decrease in the enthalpy of the system: ∆H < 0

Question 17

Define: endothermic process

Answer 17

Absorbs heat as a reactant. Increase in the enthalpy of the system: ∆H > 0

Question 18

Define: heat capacity (C)

Answer 18

The quantity of heat required to change the temperature of an object by 1 K: q/∆T = constant = heat capacity (C) [J/K]

Question 19

Define: specific heat capacity (c)

Answer 19

Quantity of heat required to change the temperature of 1 gram of a substance or material by 1 K: specific heat capacity (c) = q/m∆T [J/gK]

Question 20

Given the specific heat capacity of an object being heated, the mass or temperature change can be found along with the heat absorbed by what equation?

Answer 20

q = cm∆T

Question 21

Define: molar heat capacity (C_m)

Answer 21

Quantity of heat required to change the temperature of 1 mole of a substance by 1 K: C_m = q/n∆T [J/mol K]

Question 22

Define: calorimeter

Answer 22

A device used to measure the heat released or absorbed by a physical or chemical process.

Question 23

What is a coffee-cup calorimeter?

Answer 23

For processes that take place at a constant pressure, heat transferred may be measured with one of these: you use the equation -q_sys = q_water [in the calorimeter]

Question 24

How is the heat released during the combustion of a sample measured with a bomb calorimeter?

Answer 24

-q_rxn = q_calorimeter, where q_calorimeter = C_calorimeter ∆T_calorimeter

Question 25

Define: thermochemical equation

Answer 25

Balanced equation that includes the enthalpy change of the reaction (∆H).

Question 26

Define: Hess’s law

Answer 26

∆H_overall = ∑ ∆H_i

Question 27

Define: standard states

Answer 27

Established set of specific conditions used to reduce the number of variables when studying a reaction.

Question 28

Define: standard enthalpy of a reaction

Answer 28

∆Hº_rxn is the enthalpy change of a reaction when it is measured at the standard state. It is also called the standard heat of reaction.

Question 29

Define: formation equation

Answer 29

1 mol of a compound forms from its elements. Like C + 2H₂ → CH₄

Question 30

Define: standard enthalpy of formation

Answer 30

∆Hº_f is the enthalpy change for a formation equation when all the substances are in their standard states.

Question 31

What is the equation for the standard enthalpy of a reaction?

Answer 31

∆Hº_rxn = ∑m∆Hº_f (products) - ∑n∆Hº_f (reactants), where m and n are the amounts of products and reactants given by the coefficients in the balanced equation.