IB Chemistry Reactivity 1.1: Enthalpy and Calorimetry

Flashcards covering vocabulary, definitions, and formulas for IB Chemistry Reactivity 1.1 Enthalpy and Calorimetry based on lecture workbooks.

System

The reaction itself — the chemicals undergoing change.

Surroundings

Everything else besides the reaction, such as the solution, container, air, thermometer, and the rest of the universe.

Law of conservation of energy

The total energy of the system and surroundings is constant; energy is never created or destroyed, only transferred.

Exothermic reaction

A reaction where energy is released from the system to the surroundings ($\Delta H < 0$), causing the temperature of the surroundings to increase.

Endothermic reaction

A reaction where energy is absorbed from the surroundings into the system ($\Delta H > 0$), causing the temperature of the surroundings to decrease.

Heat ($Q$)

The energy transferred between a system and surroundings.

Temperature

A measure of the average kinetic energy of the particles in the surroundings.

Enthalpy ($H$)

The total heat energy content of the system at constant pressure.

Reaction coordinate

The x-axis on an energy profile diagram representing the progress of a chemical reaction.

Transition state

The highest energy point on an energy profile curve, corresponding to the peak of the activation energy.

Activation energy ($E_a$)

The minimum energy required for a reaction to proceed; it is always positive for both endothermic and exothermic reactions.

Thermodynamic stability

A property determined by enthalpy level; products are more stable if they have lower enthalpy (exothermic) and less stable if they have higher enthalpy (endothermic).

Standard enthalpy change of reaction ($\Delta H^\ominus$)

The heat transferred at constant pressure when a reaction occurs under standard conditions ($298\,K$, $100\,kPa$, $1\,mol\,dm^{-3}$) with all substances in their standard states.

Standard Conditions

Environmental parameters for measuring enthalpy including a temperature of $298\,K$ ($25\,^\circ\text{C}$), pressure of $100\,kPa$, and solution concentrations of $1\,mol\,dm^{-3}$.

Specific heat capacity ($c$)

The energy required to raise the temperature of a substance ($4.18\,J\,g^{-1}\,K^{-1}$ for water).

Calorimetry

The process of measuring the temperature change of a known mass of water or solution to determine enthalpy changes experimental.

Enthalpy calculation equation ($Q$)

$Q = m \times c \times \Delta T$, where $m$ is the mass of the solution, $c$ is specific heat capacity, and $\Delta T$ is the change in temperature.

Molar Enthalpy Change formula ($\Delta H$)

$\Delta H = -Q / n$, where $Q$ is heat transferred and $n$ is the amount in moles of the limiting reagent.

Plimsoll symbol ($\ominus$)

A superscript symbol used to indicate that a measurement was taken under standard conditions.

Systematic error in Calorimetry

Experimental inaccuracies, such as heat loss to the surroundings, that cause the calculated $|\Delta H|$ to be too small compared to theoretical values.