Module 1.3 The second and third law of thermodynamics

What does the second law of thermodynamics state?

All spontaneous processes increase the entropy of the universe

Equation for the entropy change of the universe ?

​∆𝑆𝑢𝑛𝑖𝑣 = ∆𝑆𝑠𝑦𝑠 + ∆𝑆𝑠𝑢𝑟

How do you calculate the entropy change of the surroundings

∆𝑆𝑢𝑛𝑖𝑣 = ∆𝑆𝑠𝑦𝑠 + 𝑞𝑠𝑢𝑟𝑟 / 𝑇

How do you determine spontaneity using ΔSuniv?

• ΔSuniv > 0 → Spontaneous

• ΔSuniv < 0 → Nonspontaneous

• ΔSuniv = 0 → Equilibrium

If the system absorbs heat wha tis the sign of qsurr​?

Negative the surroundings lose heat because the system gains it

If the system releases heat what is the sign of qsurr

The surroundings gain heat because the system releases it

Equation for calculating ΔS° of a reaction ?

∆𝑆° = Σ 𝑣 𝑆° (𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠) − Σ 𝑣 𝑆° (𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠)

What does the third law of thermodynamics state

the entroy of a pure perfect crystal at 0 k is zero