Thermochemistry Lecture Notes

This flashcard set covers the fundamental vocabulary and formulas of thermochemistry, including system definitions, heat flow signs, specific heat, and types of calorimetry.

System

A part of the universe under observation.

Surrounding

The remaining part of the Universe outside the system.

Universe

The combination of the system and surrounding ($\text{System} + \text{surrounding} = \text{universe}$).

Endothermic process

A process where heat is absorbed by the system from the surrounding, resulting in $q > 0$ ($+ve$).

Exothermic process

A process where heat is released, evolved, or given out of the system to the surrounding, resulting in $q < 0$ ($-ve$).

Combustion

The process of burning in $O_{2(g)}$; all such reactions are exothermic.

Specific heat ($c$)

The heat needed to increase the temperature of $1\,g$ of a substance by $1\,^{\circ}C$.

Unit of specific heat ($c$)

$J/g\cdot^{\circ}C$ ($\text{q} / (m\Delta T)$).

Heat capacity ($C$)

The product of specific heat and mass ($C = mc$), representing the heat capacity of the system with the unit $J/^{\circ}C$.

$$\Delta T$$

The change in temperature, calculated as $(T_{\text{final}} - T_{\text{initial}})$

Magnitude of heat flow equation

$q_{\text{system}} = mc\Delta T_{\text{system}}$ or $q = C\Delta T$.

Calorimetry

The measurement of heat flow using a device called a calorimeter.

Coffee-cup calorimeter

A device consisting of two nested polystyrene foam cups (good insulators) filled with water, where heat evolved by the reaction is absorbed by the water.

Bomb calorimeter

A completely insulated device suitable for reactions involving gases and products that reach high temperature, where a sample is ignited in a heavy-walled metal vessel called a bomb.

$q_{\text{reaction}}$ (Calorimetry)

The heat of the reaction, which is equal to the negative heat of the calorimeter ($q_{\text{reaction}} = -q_{\text{calorimeter}}$).

Bomb Calorimeter Equation

$q_{\text{reaction}} = -[C\Delta T(\text{bomb}) + mc\Delta T(\text{water})]$; if water is neglected, $q_{\text{reaction}} = -C\Delta T(\text{bomb})$.