Energetics / Thermochemistry

$0^{\circ}C$

$-273.15^{\circ}C$

$273.15^{\circ}C$

$-100^{\circ}C$

Energy is created during exothermic reactions

Energy is destroyed during endothermic reactions

Total energy of the system and surroundings remains constant

Energy can only be measured in Kelvin

$1672 \, J$

$418 \, J$

$104.5 \, J$

$400 \, J$

$+824 \text{ kJ}$

$-1648 \text{ kJ}$

$+1648 \text{ kJ}$

$-412 \text{ kJ}$

Standard enthalpy of formation

Standard enthalpy of combustion

Standard enthalpy of condensation

Standard enthalpy of atomization

Endothermic

Exothermic

At equilibrium

Non-spontaneous

1

2

3

4

$C-C$

$C-H$

$C-O$

$C=O$

The bonds in the products are exactly as strong as the bonds in the reactants

The reaction is impossible

The reaction is highly explosive

No bonds were broken or formed

$MgCl_{2}(s) \rightarrow Mg^{2+}(g) + 2Cl^{-}(g)$

$MgCl_{2}(s) \rightarrow Mg(g) + Cl_{2}(g)$

$Mg^{2+}(g) + 2Cl^{-}(g) \rightarrow MgCl_{2}(s)$

$Mg(s) + Cl_{2}(g) \rightarrow MgCl_{2}(s)$

Atomization = Bond enthalpy

Atomization = 2 $\times$ Bond enthalpy

Atomization = 0.5 $\times$ Bond enthalpy

Atomization = -Bond enthalpy

$I^{-}(g)$

$I(g)$

$I_{2}(g)$

$I^{+}(g)$

Positive

Negative

Zero

Indeterminate

Gas particles have more potential energy

Gas particles are larger

Gas particles have more ways to distribute energy (more microstates)

Gas particles have fewer vibrational modes

An increase in the entropy of the system

An increase in the total entropy of the universe

A decrease in the enthalpy of the system

An increase in the Gibbs free energy