Thermochemistry Lecture and Practice Examination Review

Vocabulary practice flashcards covering calorimetry, molar enthalpies of combustion, formation, and reaction, Hess's Law, and energetic states from thermochemistry lecture problems.

Thermal Mixing Equilibrium Temperature

The resultant equilibrium temperature reached when heat transfer occurs between two thermal masses without loss to the container or surroundings; for example, mixing $150\,\text{g}$ of water at $75^\circ\text{C}$ with $75\,\text{g}$ of water at $20^\circ\text{C}$ results in a final temperature of $57^\circ\text{C}$.

Specific Heat Capacity of Nickel ($c_{\text{Ni}}$)

The quantity of heat required to raise the temperature of one gram of nickel by one degree Celsius, specified as $0.444\,\text{J}/(\text{g}\cdot^\circ\text{C})$.

Specific Heat Capacity of Steam ($c_{\text{steam}}$)

The quantity of heat required to change the temperature of gaseous water per unit mass, given as $2.02\,\text{J}/(\text{g}\cdot^\circ\text{C})$; cooling $145\,\text{g}$ of steam from $140^\circ\text{C}$ to $124^\circ\text{C}$ requires the removal of $4.69\,\text{kJ}$ of energy.

Molar Heat of Combustion of Diethylamine

The enthalpy change when one mole of diethylamine, $(\text{C}_2\text{H}_5)_2\text{NH}$, undergoes complete combustion, defined as $3003.811\,\text{kJ/mol}$, resulting in the release of $2.05\,\text{MJ}$ (or $2053\,\text{kJ}$) when burning a $50.0\,\text{g}$ sample.

Molar Heat of Combustion of Glucose

The standard enthalpy change for the complete combustion of glucose according to the equation $\text{C}_6\text{H}_{12}\text{O}_6(g) + 6\text{O}_2(g) \rightarrow 6\text{CO}_2(g) + 6\text{H}_2\text{O}(l)$, calculated using molar heats of formation as $-2802.5\,\text{kJ/mol}$.

Molar Heat of Formation of Ethene ($\Delta_f H_m$)

The standard molar enthalpy of formation of $\text{C}_2\text{H}_4(g)$, determined to be $+52.4\,\text{kJ/mol}$ using its combustion reaction: $\text{C}_2\text{H}_4(g) + 3\text{O}_2(g) \rightarrow 2\text{CO}_2(g) + 2\text{H}_2\text{O}(g)$ with $\Delta_c H_m = -1322.9\,\text{kJ/mol}$.

Enthalpy of Combustion of Hydrazine ($\Delta_c H_m$)

The molar enthalpy of reaction for $\text{N}_2\text{H}_4(g) + 3\text{O}_2(g) \rightarrow 2\text{H}_2\text{O}(g) + 2\text{NO}_2(g)$, which equals $-4.00 \times 10^2\,\text{kJ/mol}$, yielding $40.0\,\text{kJ}$ of released energy when $3.60\,\text{g}$ of $\text{H}_2\text{O}(g)$ is formed.

Enthalpy Change of Sodium Oxide Hydration

The heat released in the reaction $\text{Na}_2\text{O}(s) + \text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(s)$, where $\Delta H = -168\,\text{J}$; producing $21\,\text{J}$ of energy corresponds to the formation of $1.0 \times 10^1\,\text{g}$ of $\text{NaOH}(s)$.

Enthalpy of Reaction for Sodium and Phosphoric Acid ($\Delta_r H$)

The net heat of reaction for $6\text{Na}(s) + 2\text{H}_3\text{PO}_4(aq) \rightarrow 3\text{H}_2(g) + 2\text{Na}_3\text{PO}_4(aq)$, determined to be $-1.80 \times 10^2\,\text{kJ}$ based on the release of $30.0\,\text{kJ}$ of energy when $1.010\,\text{g}$ of $\text{H}_2(g)$ is produced.

Molar Heat of Oxidation of Sucrose

The enthalpy released per mole of sucrose oxidized in the human body at $37^\circ\text{C}$ (assuming $\text{H}_2\text{O}$ is formed), calculated as $-3.77\,\text{MJ/mol}$ from data showing that $30.0\,\text{g}$ of sucrose provides $0.330\,\text{MJ}$ of energy.

Molar Heat of Combustion of Ammonia

The predicted enthalpy of combustion for $\text{NH}_3(g)$ to form $\text{NO}(g)$ and $\text{H}_2\text{O}(g)$, calculated via Hess's Law from component formation equations to be $-226.4\,\text{kJ/mol}$.

Stored Energy in Water Systems

The comparative total internal thermal energy contained within water phases, in which $1.0\,\text{mole}$ of $\text{H}_2\text{O}(g)$ at $100^\circ\text{C}$ stores more energy than $1.0\,\text{mole}$ of $\text{H}_2\text{O}(l)$ at $100^\circ\text{C}$ or $0^\circ\text{C}$ due to latent heat of vaporization.

Thermochemical Equation of Methane Combustion

The balanced chemical equation including enthalpy describing the burning of methane: $\text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(g)$ with a molar heat of combustion of $\Delta_c H_m = -802.3\,\text{kJ/mol}$.

Endothermic Heat of Decomposition ($\Delta_d H$ of $\text{HCl}$)

The positive enthalpy change of the decomposition reaction $2\text{HCl}(g) \rightarrow \text{H}_2(g) + \text{Cl}_2(g)$ ($\Delta_d H = +185.2\,\text{kJ}$), indicating that the system must absorb heat at constant temperature, the product bonds are weaker than reactant bonds, and $\text{HCl}(g)$ has a negative heat of formation.

Ecological Perspective

A contextual viewpoint that evaluates processes based on environmental consequences, such as assessing the statement: "The use of fossil fuels as an industrial energy source contributes to global warming."