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CHEM 1210 > Chapter 5: Thermochemistry > Flashcards

Chapter 5: Thermochemistry Flashcards

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1
Q

What does the term ‘pressure-Volume Work’ describe?

A

Work done by or to a system to exert or resist pressure in scenarios involving constant pressure

For the purposes of chapter 5, all reactions are considered to be under constant pressure in one way or another (because they either occur under constant pressure from the Earth’s atmosphere or inside of containers with lids)

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2
Q

What is the concept of enthalpy meant to describe/quantify?

A

The flow/measure of heat that occurs in a system during a reaction (like neutralization) or process (like phase change)

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3
Q

what does Hess Law state?

A

that the total enthalpy of a rxn it equal to the sum of the enthalpies of its intermediate rxns

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4
Q

what types of reactions are more accurately studied with constant PRESSURE calorimeters?

A

solutions

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5
Q

What is the equation for enthalpy?

A

H= E + PV where P is constant and E is the system’s total energy

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6
Q

What are the base units for Newtons?

A

N = kg(m/s^2)

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7
Q

What does ‘Internal Energy’ refer to?

A

The sum of a system’s total energy: heat plus work

where heat and work can both have positive or negative values, depending on the situation

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8
Q

What are the 3 state functions related by the concept of enthalpy (H)?

A

Pressure
Volume
Energy

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9
Q

What is the purpose of the concept of ‘Enthalpy’

A

‘Enthalpy’ allows us to relate the state functions pressure, volume, and energy in a way that lets us set DELTA enthalpy equal to q when a system is under constant pressure

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10
Q

What is the gist of the First law of thermodynamics?

A

that energy cannot be created or destroyed; it has to come from somewhere and go to somewhere

By extension: Heat/work gained by the system is lost by the surroundings (and vice versa)

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11
Q

why doesn’t the expression for the heat capacity of constant volume/bomb calorimeters include mass?

A

because Ccal is based the heat capacity of the entire machine, not by the heat capacity of individual grams or moles of the water it contains

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12
Q

Does Potential Energy pertain to motion, temperature, storage, or intermolecular attraction?

A

Stored energy (related to position) that can be converted to kinetic energy

Has types: gravitational potential energy (pertains to objects), chemical (pertains to energy stored in chemicals that can be used to do work), electrostatic (pertains to charged particles), and spring/elastic (pertains to energy stored in things that are stretched or compressed)

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13
Q

what does Calorimetry measure?

A

the heat transfer (delta enthalpy) between a system and its surroundings based on the magnitude of the temperature changes that occur

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14
Q

what does ThermoCHEMISTRY examine?

A

the Transformation of energy (especially heat) in chemical rnxs

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15
Q

Is enthalpy considered a state function?

A

yes, because it is composed of/relates 3 state functions: E, P, V

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16
Q

Is the water in a calorimeter a solution?

A

No. water is a compound.

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17
Q

Why/when is it that in thermo calculations, ‘work’ can cancel with -‘PdeltaV’?

A

In DELTA!!! enthalpy calculations, when pressure is constant, work = - work, and thus cancels in the equation

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18
Q

How many joules are in 1 Calorie?

A

1 calorie = 4.184J

Amount of energy needed to RAISE 1 gram of water by 1 degree

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19
Q

what types of reactions are more accurately studies with constant VOLUME calorimeters?

A

combustions

20
Q

What are joules units for?

A

energy

21
Q

What is the gist of the equation for delta enthalpy of reaction?

A

net heat = heat require to produce products - heat required to react reactants

22
Q

In a calorimetry experiment involving solutions, what/whose heat capacity issued for heat calculations?

A

The water’s heat capacity is used (provided the solution is considered dilute)

23
Q

what does Molar heat capacity describe/quantify?

A

the amount of Energy req to RAISE 1 mol of a material by 1 degree (celsius or kelvin)

24
Q

What is the term ‘Energy’ meant to describe?

A

The ‘fuel’ needed to do work or transfer heat (where work is energy transfer involving motion and heat is energy transfer involving temperature change)

25
Q

What does it mean to call something a ‘State Function’?

A

that the Function is not dependent on direction/history

26
Q

what does Specific heat describe/quantify?

A

the amount of Energy req to RAISE 1 gram of a material by 1 degree (celsius or kelvin)

27
Q

What is Thermodynamics the study of?

A

Study of energy and its transformations

28
Q

True or false: (as it relates to calorimetry), qsln = -qrxn

A

true (as the ‘solution’ is composed of the water, the reactants, AND products)

29
Q

In a calorimetry experiment involving solutions, what is considered the system?

A

The reactants and products

30
Q

What is the standard enthalpy of formation value (in kJ) for pure elements?

A

usually 0

31
Q

what does Standard Enthalpy of formation describe/quantify?

A

Enthalpy involved in making 1 mol of compound from the standard forms of its component elements

32
Q

how do bond enthalpies related to enthalpy of reaction?

A

the net sum of a reaction’s bond enthalpies is APPROX. equal to the enthalpy of reaction

33
Q

Does Kinetic Energy pertain to motion, temperature, storage, or intermolecular attraction?

A

motion

Not the same thing as work

34
Q

What are the units for work?

A

Joules

35
Q

In which calculation/equation does the ‘work’ term cancel with -‘PdeltaV’?

A

Delta enthalpy

NOT delta internal energy!!!

36
Q

How many types of (delta) enthalpy are there?

A

At least 6:

heat of combustion
heat of formation
heat of neutralization
heat of reaction
heat of solution
heat of transformation (phase change)
37
Q

what does Heat capacity describe/quantify?

A

the amount of Energy req to RAISE the total mass of a material by 1 degree (celsius or kelvin)

38
Q

What is the term ‘Heat’ meant to describe?

A

the Energy flow involved in changing something’s temperature

Transfer of energy (from a hotter material to a colder one)

39
Q

what does bond enthalpy describe/quantify?

A

the enthalpy/heat flow required in making/breaking each bond in a chemical reaction

40
Q

In a calorimetry experiment involving solutions, what is considered the surroundings?

A

The water

41
Q

What is the term ‘work’ meant to describe?

A

the Amount of energy required to move something against a force

42
Q

Which of these is NOT a state functions related by the concept of enthalpy (H): q, V, P, E

A

q

43
Q

Is atmospheric pressure considered content, or not constant?

A

constant

44
Q

What is the equation for DELTA enthalpy?

A

deltaH = deltaE + [-P(delta V)

45
Q

what is the ‘bomb’ in a bomb calorimeter?

A

a little insulted cup/vessel that has electrical leads (for adding heat) and valve (for receiving oxygen) so that when you put a sample inside, and then put the whole thing inside the calorimeter, and then burn the sample, the heat gained by the calorimeter can be measured.

46
Q

What are newtons (N) units for?

A

force

47
Q

What are the base units for a Joule?

A

N * m

where N = kg(m/s^2)

CHEM 1210 (18 decks)

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