CHEM1100 Final

Assumptions for an ideal gas

Molecules have negligible volume

No intermolecular interactions

Molecules move in random motion

When does ideal gas behaviour break down?

High pressure and/or low temperature

HP LT!!!

Open system

Can exchange matter and energy w surroundings

Closed system

Can only exchange energy w surroundings

Isolated system

Cannot exchange matter or energy w surroundings

Adiabatic system

Can only exchange work with surroundings

Positive w means

work done by surroundings on the system

Is internal energy (U) a state function

Yes

Is enthalpy a state function?

Yes

Standard enthalpy of formation for an element

0J

Is entropy a state function?

Yes (delta S = final S - initial S)

Relationship between entropy of surroundings and change in reaction enthalpy

Third law of thermodynamics

At absolute zero, the entropy of a perfectly ordered pure crystalline substance is zero.

System at equilibrium has delta G of…

0J

At a phase change, delta G is

0J

Which quantity cannot be measured directly?

Standard Gibbs Energy Change

Is G a state function

Yes

When is G a minimum?

When a system is in equilibrium

Molar enthalpy of fusion

Heat needed to melt 1 mol of substance at normal melting point

Heat needed to vaporise 1 mol of substance at its normal boiling point

Molar enthalpy of sublimination

Heat needed to vaporise 1 mol of substance from solid phase

Axis on phase diagram

Steps to dissolving a gas

1. Form pockets in solvent to hold gas (endothermic bc imf are overcome between solvent molecules)

2. Mixing - gas goes into pockets, create IMF between solute and solvent (exothermic)

Colligative properties - freezing point ___ (and why is this the case)

Depression

Solute will be in liquid phase. Solute disrupts process of forming interactions btwn solute to reform solid

So melting point is lower

Boiling point ___

Elevation

Ions in liquid prevent solvent molecules from entering gas phase

More energy needed to enter gas phase

how to calculate b for colligative properties

b = molality

For nondissociating solutes (ions)

b = moles of solute / mass of solVENT

moles/kilogram

Do colligative properties depend on the identity of particles?

NO

Only depends on quantity of particles (b)

Cell notation rules

Carbon oxidation state rules

• C-C bonds don’t change oxidation state

• Each bond with H or metal = -1

• Each bond with electronegative element (NOF or halogens) = +1

Is work a state function

No

Is heat a state function

No

The formula that Lucas wanted me to add in

delta H = delta U + RT delta n

delta n = change in number of moles

Intensive property

A characteristic that does NOT depend on the amount present

YIPPAROONI THAT IS ALL!!! Flip over this card for a reward

What does “free” mean for gibb’s free energy

Energy that can be transferred in forms other than heat and PV work