Thermochemistry

Question 1

What are isolated, closed, and open systems?

Answer 1

isolated: cannot exchange energy or matter with surrounding closed: can exchange energy but not matter with surroundings open: can exchange energy and matter with surroundings

Question 2

What is the area under a pressure-volume graph equal to?

Answer 2

work

Question 3

What does 1st law of thermodynamics become for an isothermal process?

Answer 3

W=Q since when change in T = 0, change in U = 0

Question 4

what does 1st law of thermodynamics become for an adiabatic process?

Answer 4

change in U = -W since when no heat exchange between system and environment, Q = 0 in other words, change in U equals work done “ON” the system (the negative of the work done “BY” the system)

Question 5

What does the curve of an isothermal process look like on a pressure-volume graph?

Answer 5

hyperbolic curve

Question 6

What does an isobaric process appear as on a pressure-volume graph?

Answer 6

a flat line pressure is constant

Question 7

What does the 1st law of thermodynamics become for an isochoric/isovolumetric process?

Answer 7

change in U = Q since when no change in volume, no work is done by the system

Question 8

what does an isochoric/isovolumetric process look like on a pressure-volume graph?

Answer 8

a vertical line volume is constant

Question 9

What are standard conditions, and what problems are they used for?

Answer 9

25 degrees Celsius, 1 atm, 1 M kinetics, equilibrium, thermodynamics

Question 10

what are standard temperature and pressure, and what problems are they used for?

Answer 10

0 degrees Celsius, 1 atm ideal gas calculations

Question 11

what is the definition of boiling point?

Answer 11

the temperature at which the vapor pressure equals the ambient pressure

Question 12

what is the critical point on a phase diagram?

Answer 12

the point at which there is no distinction between liquid and gas phases

Question 13

How does sweat help prevent overheating?

Answer 13

evaporation is an endothermic process, so heat energy is absorbed from the body by the sweat so that sweat particles gain enough kinetic energy to evaporate

Question 14

What is heat (Q)?

Answer 14

the transfer of energy from one substance to another due to their difference in temperature

Question 15

Under what condition is enthalpy equivalent to heat?

Answer 15

constant pressure

Question 16

what is calorimetry?

Answer 16

the way of measuring the transfer of heat

Question 17

what is the definition of specific heat?

Answer 17

the amount of energy required to raise the temperature of 1g of a substance by 1 degree

Question 18

what is heat capacity?

Answer 18

mass times specific heat

Question 19

what is the process to solve heat transfer problems? ex. mix two substances with different temperatures and determine equilibrium temperature

Answer 19

1. q_cold = -q_hot
2. mcAT = mc(-AT)
3. AT_cold = T_f - initial T

AT_hot = initial T - T_f

Question 20

what type of calorimeter is used to determine heat of combustion?

Answer 20

bomb calorimeter or decomposition vessel

constant volume calorimetry –> work is zero

Question 21

what is the heat of fusion?

Answer 21

the enthalpy change to melt a mole of a solid

Question 22

what is heat of vaporization?

Answer 22

the enthalpy change to turn a mole of liquid to gas

Question 23

what is standard heat of formation?

Answer 23

enthalpy required to form one mole of compound from its constituent elements in their standard states

Question 24

what is standard heat of reaction?

Answer 24

enthalpy change that occurs when reaction is carried out under standard conditions

Question 25

what is bond dissociation energy or bond enthalpy?

Answer 25

average energy required to break a particular bond between atoms in the gas phase (endothermic)

Question 26

what is standard heat of combustion?

Answer 26

enthalpy change that occurs for the combustion of one mol of a fuel

Question 27

what is the second law of thermodynamics? what is entropy?

Answer 27

energy spontaneously disperses from being localized to being spread out if it is not hindered from doing so. In other words, entropy of universe is increasing.

entropy is the measure of this dispersal at a specific temperature