M2 - Chem thermodynamics II Flashcards

1
Q

What is a spontaneous process?

A

A reaction that starts without any external help

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2
Q

Why was it though that initially exothermic reactions were spontaneous?

A

Due to the natural release/lowering of E of system overall

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3
Q

General rule about spontaneity

A

If the reaction is spontaneous one way, it probably isnt the other way

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4
Q

What is Entropy (S)

A

Measure of the possible arrangements of particles in a system

Measure of disorder

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5
Q

What results in increase in Entropy?

A

When there is a less chance of system being ordered, the system spontaneously becomes disordered

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6
Q

What does a system with less entropy look like?

A

It is an ordered system where the particles are arranged and there are only few ways it can be moved

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7
Q

What is the 2nd law of thermodynamics

A

When a spontaneous event takes place in the universe, the entropy of the universe increases

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8
Q

What does the universe consist of?

A

The system of interest + surroundings

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9
Q

How can the entropy of a system spontaneously decrease?

A

If the entropy of the surroundings of the system increase by a larger amount

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10
Q

Enthalpy and entropy relationship in the universe

A

Enthalpy of the universe i.e the E is constant but the E is constantly being dispersed into the system so Entropy if the universe is increasing

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11
Q

Third law of thermodynamics

A

At absolute 0, entropy of a pure crystalline substance = 0 i.e no disorder of the substance

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12
Q

Can we measure entropy of a substance unlike enthalpy (exact heat capacity? of a substance)

A

Yes

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13
Q

What is standard entropy?

A

Entropy under standard conditions i.e 1 bar atmospheric pressure/ 1mol/L

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14
Q

What are the units of entropy

A

J/mol K

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15
Q

What is the difference between standard formation in enthalpy vs between standard formation of Entropy?

A

For enthalpy of element in standard conditions = 0 because its made of its constituent elements BUT

For entropy of element is standard conditions ≠ 0 because at 0K, elements don’t usually exist as a pure crystalline solid (ref. 3rd law of thermodynamics)

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16
Q

∆rSº =

A

∑[Sº(products)] - ∑[Sº(reactants)]

17
Q

What determines spontaneity?

A

Both ∆H and ∆S

18
Q

What is Gibbs E

A

∆G = ∆H - T∆S

19
Q

Why do we use ∆G and not G

A

Because we cannot accurately measure H and this would affect G so we talk in terms of ∆