Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DAT GenChem > GenChem6 (Thermochemistry) > Flashcards

GenChem6 (Thermochemistry) Flashcards

1
Q

Aspect of chemistry that helps determine whether a reaction is spontaneous

A

Thermodynamics/thermochemistry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

A reaction that can occur under a given set of conditions without outside assistance is said to be

A

Spontaneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A system that cannot exchange energy or matter with the surroundings, like an insulated bomb reactor

A

Isolated system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

A system that can exchange energy but not matter with the surroundings, like a steam radiator

A

Closed System

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

A system that can exchange both matter and energy with the surroundings, like boiling water

A

Open System

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

a process that occurs when the temperature of the system remains constant

A

Isothermal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

A process that occurs when no heat exchange occurs

A

Adiabatic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

A process that occurs when the pressure of a system remains constant

A

Isobaric

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A form of energy that can easily transfer to or from a system; the result of a temperature difference between the system and its surroundings

A

Heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Reactions that absorb heat energy are

Reactions that release heat energy are

A

Endothermic

Exothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

This measures heat changes

A

Calorimetry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the equation for the heat absorbed or released in a given process

A

q=mcΔT

m=mass, c=specific heat, ΔT=change in temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Type of calorimetry where the volume remains constant

Type of calorimetry where the pressure remains constant

A

Constant-volume calorimety

Constant-pressure calorimetry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the equation for measuring the q of a reaction with constant volume-calorimetry?

A

qrxn=-(qwater+qsteel)

q=mcΔT

Note that q of the entire system =zero (for review, page 352)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Properties whose magnitude depends only on the initial and final states of the system, and not on the path of the change, are known as

A

State Function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the state functions? (7)

A

Pressure, temperature, volume, enthalpy (H) entropy (S), free energy (G) and internal energy (E or U)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are standard conditions for measuring the enthalpy, entropy, and free energy of a reaction?

A

25 degrees C and 1 atm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

A substance in its most stable form under standard conditions is said to be in its

A

Standard State

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The term to express heat changes at constant pressure (typically 1 atm)

A

Enthalpy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the equation for the enthalpy change of a reaction using standard heat of formation?

A

ΔH(rxn)=H(prod) - H(react)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

A positive ΔH corresponds to anexothermic/endothermic process

A negative ΔH corresponds to an endothermic/exothermic process

A

endothermic

exothermic

22
Q

Defined as the enthalpy change that would occur if one mole of a compound were formed directly from its elements in their standard states

A

ΔH(f), enthalpy of formation

23
Q

What is the ΔH(f) of an element in its standard state

A

0

24
Q

Defined as the hypothetical enthalpy change that would occur if the reaction were carried out under standard conditions

A

ΔH°(rxn)

25
Q

What is the formula for ΔH°(rxn) using standard heat of formation?

A

ΔH°(rxn)=sum of ΔH°f(prod) - sum of ΔH°f(react)

26
Q

What value is used for Hess’s law

A

heat of vaporization, ΔH°(vap)

27
Q

an average of the energy required to break a particular type of bond in one mole of gaseous molecules

Bond breakage is always exothermic/endothermic

A

Bond Dissociation energy

endothermic

28
Q

There is one more ΔH° value, what is it.

A

Heat of combustion

29
Q

Defined as a measure of the disorder, or randomness, of a system.

What are the units of it?

A

Entropy

J/K or cal/K (energy/temperature)

30
Q

A system reaches its maximum entropy at ______, a state in which no observable change takes place as time goes on. What is the equation for ΔS(universe)

ΔS(universe) is _______ for a reversible process

A

ΔS(universe) = ΔS(system) + ΔS(surroundings) = 0

ΔS(universe)=0

31
Q

The thermodynamic state function that combines the two factors that affect to spontaneity of a reaction (ΔH and ΔS), it represents the maximum amount of energy released by a process, occurring at constant temperature and pressure, that is available to perform useful work.

A

G (Gibbs free energy)

32
Q

What is the equation for ΔG

A

ΔG=ΔH-TΔS

Get Higher Test Scores

33
Q

What does TΔS represent?

A

The total amount of heat absorbed by a system when its entropy increases reversibly

34
Q

Is free energy at a minimum or maximum at equilibrium?

What range of G can a reaction occur spontaneously?

A

Free energy is at a minimum in the equilibrium state

ΔG<0 (negative values)

35
Q

If ΔG is zero, the system is in a state of

What equation can be used in the circumstance

If ΔG is positive, the reaction is

A

equilibrium

ΔH=TΔS

non-spontaneous, but spontaneous in the reverse direction

36
Q

If ΔH is negative and ΔS is positive, what can be said about the spontaneity of the reaction?

A

Spontaneous at all temperatures

37
Q

If ΔH is positive and ΔS is negative, what can be said about the spontaneity of the reaction?

A

Non-spontaneous at all temperature

38
Q

If ΔH is positive and ΔS is positive, what can be said about the spontaneity of the reaction?

A

Spontaneous at high temperatures

39
Q

If ΔH is negative and ΔS is negative, what can be said about the spontaneity of the reaction?

A

Spontaneous at low temperatures

40
Q

What does the rate of a reaction depend upon?

A

Activation energy, not ΔG

41
Q

What are the parameters of standard free energy, or ΔG°

A

25°C, 1atm, all concentrations at 1M

42
Q

The free energy change that occurs when 1 mol of a compound in its standard state is formed from its elements in their standard states under standard conditions is

A

ΔG°(f), standard free energy

43
Q

The standard free energy of formation of any element in its most stable state/form is

A

0

44
Q

The free energy change that occurs when a reaction is carried out under standard state conditions, ie when th ereactants in their standard states are converted to produts in their standard states at standard conditions of T and P

A

ΔG°(rxn) or the standard energy of a reaction

ex: conversion of C(diamond) to C(graphite) is spontaneous, but very slow.

45
Q

What is the equation for ΔG°(rxn)?

A

ΔG°(rxn) = sum of ΔG°(f) of products- sum of ΔG°(f) of reactants

46
Q

The equation for ΔG°(rxn) derived from the equilibrium constant is

A

ΔG°(rxn) = -RT(lnKeq)

47
Q

Once a reaction commences, the standard state conditions no longer hold. Keq must be replaced by another parameter… the

A

reaction quotient

48
Q

What is the equation for the reaction quotient

A

Q= ([C]^c[D]^d)/([A]^a[B]^b)

for equation aA + bB —> cC + dD

49
Q

What is the equation for ΔG when standard state conditions no longer hold?

A

ΔG= ΔG° +RT in Q

50
Q

For the equation

2C6H6 (l) + 15O2 (g)—> 12CO2(g) + 6H2O(g) + heat

is the reaction spontaneous? Which side has greater entropy?

A

The reaction is spontaneous because heat is released, and there are more moles of gas on the right side of the equation.

DAT GenChem (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions