Chemical Energetics

The enthalpy of formation of an element in its standard state (e.g., $O_2(g)$) is defined as:

What must be true for a reaction to be classified as endothermic?

Which of these is a typical example of an exothermic reaction?

If a reaction absorbs $150 kJ$ to break bonds and releases $100 kJ$ when forming bonds, the net energy change is:

An unknown reaction $X + Y \rightarrow Z$ is found to have $\Delta H = +120\ kJ/mol$. Which statement is true?

Which of these factors does NOT affect the total enthalpy change of a reaction?

What happens to the bonds in the reactants during a chemical reaction?

The enthalpy of neutralization for a strong acid and strong base is approximately $-57\ kJ/mol$. Why is the enthalpy of neutralization for $HF(aq)$ and $NaOH(aq)$ slightly more exothermic ($-68\ kJ/mol$)?

A $5.00\ g$ sample of liquid water at $25.0^{\circ}C$ absorbs $1.00\ kJ$ of heat. What is the final temperature of the water? ($c = 4.18\ J/g^{\circ}C$)

Calculate the heat of combustion of propan-1-ol ($C_3H_7OH$) using the following bond energies: $C-H = 413, C-C = 347, C-O = 358, O-H = 463, O=O = 495, C=O = 799$. (Note: Use $O=O$ for $O_2$ and $C=O$ and $O-H$ for $CO_2$ and $H_2O$ products respectively).

What is the standard state of oxygen at $298\text{ K}$ and $100\text{ kPa}$?

In a calorimetry experiment, the 'surroundings' usually refers to:

Which factor describes the heat energy change of a reaction carried out at constant pressure?

If a reaction has a $\Delta H$ of $+60\text{ kJ/mol}$, what is the energy change for the reverse reaction?

Which of the following represents an endothermic process on a molecular level?

Which transition represents the standard enthalpy of sublimation of iodine?

Which of the following statements about Hess's Law is correct?

What is the enthalpy change for the reaction $CO_{2}(g) + H_{2}(g) \rightarrow CO(g) + H_{2}O(g)$ given: $\Delta H^{\theta}_{f} [CO_{2}] = -393.5\,kJ/mol$ $\Delta H^{\theta}_{f} [CO] = -110.5\,kJ/mol$ $\Delta H^{\theta}_{f} [H_{2}O(g)] = -241.8\,kJ/mol$

Given the following standard enthalpy changes of combustion: $C(s) = -394\,kJ/mol$ $H_{2}(g) = -286\,kJ/mol$ $CH_{3}OH(l) = -726\,kJ/mol$ Calculate the enthalpy of formation of methanol ($CH_{3}OH$).

Which of the following enthalpy changes corresponds to the equation: $S(s) + \frac{3}{2}O_{2}(g) \rightarrow SO_{3}(g)$?

What happens to the temperature of the surroundings during an endothermic reaction?

Calculate the $\\Delta H$ for a reaction where the reactant bond energies sum to $2000\ kJ/mol$ and product bond energies sum to $2500\ kJ/mol$.

Which equation correctly represents the breaking of a fluorine molecule bond?

When atoms come together to form a bond, the stability of the system:

If the $\Delta H$ for the reaction $A \rightarrow B$ is $+50\ kJ/mol$, and the energy to break bonds in $A$ is $250\ kJ/mol$, what is the energy released when bonds in $B$ form?

Which of these molecules has the highest total bond energy per molecule?

Calculate the $\Delta H$ for the complete combustion of 1 mole of propane ($C_{3}H_{8}$) given:

$C-H = 413, C-C = 347, O=O = 495, C=O = 805, O-H = 463\ (all\ in\ kJ/mol)$

Determine the enthalpy change for the reaction $2H_{2}(g) + O_{2}(g) \rightarrow 2H_{2}O(g)$ given $H-H: 436, O=O: 495, O-H: 463\ kJ/mol$.

Which transition in the nitrogen-hydrogen system requires the most energy absorption?

Using bond energies: $C-H: 413, C=C: 614, C-C: 347, Cl-Cl: 242, C-Cl: 339\ kJ/mol$. Calculate the enthalpy change for the addition of chlorine to ethene: $C_{2}H_{4}(g) + Cl_{2}(g) \rightarrow C_{2}H_{4}Cl_{2}(g)$.