Thermodynamics

Question 1

IDEAL GASES

Answer 1

PV = nRT

Question 2

Gas constant (R)

Answer 2

8.3145 LkPa/Kmol

Question 3

What does a high temp correlate to for pressure?

Answer 3

A higher temperature would increase the kinetic energy of the atoms.

Therefore the atoms would move faster and collide more (INCREASING PRESSURE)

Question 4

What does a low temperature correlate to for pressure?

Answer 4

A low temperature would mean that the atoms have a low kinetic energy and therefore MOVE SLOWER.

Less Collisions = Lower pressure

Question 5

1 ATM

Answer 5

101325 Pa
or
101.325 kPa

Question 6

STP

Answer 6

Standard Temperature & Pressure.
* 0°C or 273 k
* 1 ATM

Question 7

ΔU

Answer 7

• ΔU = q + w
• ΔU = q +pΔV
• ΔU = C x ΔT

Question 8

How would ΔU be demonstrated if the surroundings gain 10.80kJ ?

Answer 8

ΔU = - 10.8 kJ

negative value

Question 9

How would ΔU be demonstrated if the system gains 10.80kJ ?

Answer 9

ΔU = 10.8kJ

positive value

Question 10

First law of thermodynamics

Answer 10

ΔU = Q - W

Question 11

Precision

Answer 11

The consistency of results with each other

Question 12

Accuracy

Answer 12

The consistency of results with the true value

Question 13

In regard to entropy, how does it determine the direction of a reaction?

Answer 13

A reaction will always proceed in the direction of increasing disorder .

Question 14

TRUE OR FALSE

A reaction proceeds in the direction of increased orderliness

Answer 14

FALSE

A reaction always proceeds in the direction of increased disorder.

Question 15

Define…

Entropy

Answer 15

The degree of measure of disorder in a system.

Question 16

TRUE OR FALSE

Generally, in high temperatures there is a higher level of disorder

Answer 16

TRUE

Question 17

Second law of thermodynamics

Answer 17

The change in entropy of a system must be greater than 0 for a spontaneous change to occur.

• ΔS_tot = ΔS_sys + ΔS_sur < 0: non-spontaneous
• ΔS_tot = ΔS_sys + ΔS_sur > 0 : spontaneous

Question 18

TRUE OR FALSE

During a spontaneous change in an isolated system, the entropy decreases.

Answer 18

FALSE

For isolated systems, the entropy always increases during a spontaneous change. ΔS_tot > 0

Question 19

Change in entropy [ΔS]

Answer 19

• ΔS = q_rev / T
• ΔS = ΔH / T

Question 20

TRUE OR FALSE

There is NO DISORDER at 0 kelvin

Answer 20

TRUE

Question 21

Third law of thermodynamics

Answer 21

There is no entropy at absolute zero.

Question 22

Formula

Gibbs free energy

Answer 22

• G = H - TS
• ΔG = ΔH - TΔS

Question 23

Criterion of spontaneity

Answer 23

ΔS
* ΔS > 0 : Spontaneous
* ΔS < 0 Non-spontaneous

ΔG
* ΔG < 0 : Spontaneous
* ΔG > 0 : Non-spontaneous

Question 24

Coupled reactions

Answer 24

Reactions that are energetically unfavourable can be ‘coupled’ with favourable reactions.

This can be achieved when the overall change in standard gibbs free energy is negative (therefore spontaneous/favourable)

Question 25

Δr_G°

Answer 25

Δr_G° = -RT lnK | R (universal constant) = 8.31 J/Kmol

Question 26

# TRUE OR FALSE At equilibrium ΔrG = 0

Answer 26

**TRUE**

Question 27

Δr_G

Answer 27

Δr_G = Δr_G° + RT lnK

Question 28

Equilibrium constant [K]

Answer 28

**K** = ( **C** *^c* ) ( **D** *^d* )/ (**A** *^a*) ( **B** *^b*)

Question 29

Molar gibbs energy

Answer 29

Gm = G/n * n = number of moles * G = Gibbs free energy

Question 30

# Formulas... Enthalpy

Answer 30

* H = U + PV * H =

Question 31

Triple point

Answer 31

The point in which the substance exists in all three phases at the same time in equilibrium.

Question 32

Critical point

Answer 32

The **temperature** and **pressure** point on a phase diagram where the LIQUID and GASEOUS phases of a substance merge together into one substance called the **supercritical fluid**

Question 33

Gibbs phase rule

Answer 33

The number of intensive variables that must be defined to determine the state of a system. **F = C - P + 2**

Question 34

Intensive variable

Answer 34

A variable that is **NOT** dependent on the quantity of the system (**e.g.** water) | E.g. : **Pressure**, **Density**, **Temperature**

Question 35

Extensive variable

Answer 35

A variable that is dependent on the quantity of the system | E.g. : **Volume**, **Mass**, **number of moles**

Question 36

# TRUE OR FALSE Determining a state requires all the variables of a system

Answer 36

**TRUE**

Question 37

Gibbs phase rule formula

Answer 37

**F = C - P +2** * F = # of intensive variables * C = # of components * P = # of phases

Question 38

Clausius-Clapeyron equation

Answer 38

Δln p / ΔT = Δ_evap_ H / RT^2

Question 39

chemical potential

Answer 39

μ_A = μ°_A + RT lnX_A

Question 40

How can you determine the gibbs free energy of a reaction?

Answer 40

G = (n_A)(μ_A ) + (n_B)(μ_B)

Question 41

# TRUE OR FALSE Raising the temperature on an exothermic reaction will shift the equilibrium to the right

Answer 41

**FALSE** There will be more heat on the product side so the equilibrium will counter by shifting to the **reactants / left**

Question 42

Van't Hoffs equation | Normal

Answer 42

ln(K2/K1) = ΔH/R (T2-T1/T2T1)

Question 43

Van't Hoff equation | In respect to ΔH

Answer 43

ΔH = R ln(K2/K1) (t2t1/t2-t1)

Question 44

Clausius-clapeyron equation

Answer 44

Ln(P2/P1)= ΔH/R (T2-T1/ T2T1) * P = vapor pressure

Question 45

# TRUE OR FALSE Increasing the temp for an Endothermic reaction shifts to the right

Answer 45

**TRUE**

Question 46

# TRUE OR FALSE The reaction shifting to the reactants means the reactants decrease

Answer 46

**FALSE** The reactants will increase if the reaction shifts towards them.

Question 47

Le chatelier’s principle

Answer 47

**Endothermic reaction** * Increase temp = more products * Decrease temp = more reactants **Exothermic reaction** * Increase temp = more reactants * Decrease temp = more products