Thermodynamics Flashcards

1
Q

When two objects reach thermal equilibrium, that means their _______________ and ______________ are equal.

A

Temperatures; average kinetic energy

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2
Q

In a calorimeter, energy is transferred between
(2 possibilities)

A

1) one chemical species and another chemical species (ex. hot iron ball in water)

2) a chemical reaction and an aqueous solution (ex. dissolving ammonium nitrate in water lab)

NO ENERGY IS LOST FROM THE CALORIMETER UNLESS THE QUESTION PROMPTS YOU IN THAT DIRECTION.

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3
Q

Heat capacity (c) can have units including

A

mass, moles, or neither. Watch your units carefully in thermo!

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4
Q

Exothermic processes

A

ΔH < 0
Surroundings feel hot
Temperature of surroundings increases

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5
Q

Endothermic process

A

ΔH > 0
Surroundings feel cold
Temperature of surroundings decreases

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6
Q

ΔH°rxn formula from bond energies

A

ΔH°rxn = broken – formed

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7
Q

Breaking attractions is always

A

endothermic.

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8
Q

Forming attractions is always

A

exothermic.

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9
Q

ΔH°rxn from ΔH°f values requires you multiply the

A

ΔH°f values by the coefficients in the balanced chemical equation.

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10
Q

ΔH°rxn formula related to energy transferred and moles of rxn

A

ΔH°rxn = –qsurr/molrxn

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11
Q

If a reaction is exothermic, the bonds in the __________ are stronger/more stable.

A

Products

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12
Q

ΔH°fus is used during what phase change?

A

Melting

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13
Q

–ΔH°fus is used during what phase change?

A

Freezing

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14
Q

ΔH°vap is used during what phase change?

A

Vaporization

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15
Q

–ΔH°vap is used during what phase change?

A

Condensation

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16
Q

When the coefficients of a reaction are doubled, the ΔH°rxn should be

A

doubled.

17
Q

When a reaction is flipped, the ΔH°rxn should be

A

changed in sign (pos to neg or neg to pos).

18
Q

When reactions are added together, you should

A

add the values of ΔH°rxn.

19
Q

A process is thermodynamically favorable if ΔG°rxn is __________ zero.

A

Less than

20
Q

A process being thermodynamically favorable and having a positive ΔH°rxn and a positive ΔS°rxn is

A

entropy driven.

21
Q

A process being thermodynamically favorable and having a negative ΔH°rxn and a positive ΔS°rxn is

A

both enthalpy and entropy driven.

22
Q

ΔH°rxn and ΔS°rxn usually have ____________ units of energy.

A

Different

Note: ΔH°rxn is normally in kJ and ΔS°rxn is normally in J.

23
Q

When non-standard Gibbs, ΔGrxn, is equal to zero, the reaction is

A

at equilibrium.

24
Q

When calculate ΔG°rxn from K or vise-versa, ΔG°rxn must be in energy units of

A

J (NOT kJ).

25
Q

When ΔG°rxn < 0 but no rxn is observed to occur in the lab, the reaction is termed _______________ controlled and is due to ________________.

A

Kinetically controlled; high activation energy