5.2.2 - Enthalpy and entropy Flashcards Preview

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Flashcards in 5.2.2 - Enthalpy and entropy Deck (15)
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1
Q

Entropy

A

Measure of the dispersal of energy in a system

2
Q

When is entropy higher

A

The more disordered or random something is

3
Q

Why do gases have the most entropy

A

Particles are moving rapidly and randomly

S (gas)&raquo_space; S (liquid) > S (solid)

4
Q

2nd law of thermodynamics

A

Entropy naturally increases over time

Cannot decrease

5
Q

3rd law of thermodynamics

A

Entropy of a substance is zero at absolute zero (0K) as it has a perfect order

6
Q

The higher the temperature ..

A

The faster the particles vibrate/move and so the greater the entropy (disorder )

7
Q

Where are the biggest increases in entropy

A
State changes (melting and boiling)
Esp boiling due to a large amount of disorder in gases compared to solids and liquids
8
Q

Why does water have a low entropy

A

H bonds - spp bond angle (180)

9
Q

When does entropy decrease

A

When you go from disorder to order

10
Q

Calculating entropy change

A

Sum S products - Sum S reactants

S is +ve - increase in entropy
S is -ve - Decrease in entropy

11
Q

Gibbs free energy change

A

G = delta formation - T (S)

T in Kelvin
H/S in joules per mole
G in kJ/mol

12
Q

When is a reaction feasible

A

If G is less than or equal to 0

13
Q

Why may a feasible reaction not actually take place

A

High activation energy

14
Q

Spontaneous processes

A

Physical or chemical processes that occur w/out outside intervention

15
Q

Predicting general change of entropy

A

X moles of s/l/g forms X moles of s/l/g

… has higher/lower disorder and the entropy of the p/r is higher /lower than the r/p