AP Chemistry Flashcards: Introduction To Enthalpy Of Reaction

What this deck covers

This deck focuses on Introduction To Enthalpy Of Reaction, giving you a quick way to review the definitions, rules, and examples that matter most for AP Chemistry.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: State the formula for change in enthalpy ($\Delta H$).

Answer: $\Delta H = H_{products} - H_{reactants}$. Difference between final and initial enthalpy states.

Flashcard 2: Which principle states that the total energy of an isolated system remains constant?

Answer: The First Law of Thermodynamics. Conservation of energy in closed systems.

Flashcard 3: Calculate the $\Delta H$ for the decomposition of $2$ moles of $H_2O_2$ given $\Delta H = -196$ kJ/mol.

Answer: $\Delta H = -392$ kJ. Multiply per-mole enthalpy by number of moles reacting.

Flashcard 4: What is the enthalpy change ($\Delta H$) when one mole of water vapor condenses?

Answer: $\Delta H = -40.7$ kJ/mol. Reverse of vaporization with opposite sign.

Flashcard 5: What does a positive $\Delta H$ indicate about a reaction?

Answer: A positive $\Delta H$ indicates an endothermic reaction. Heat is absorbed from the surroundings during the reaction.

Flashcard 6: What is the enthalpy of vaporization?

Answer: It is the enthalpy change when one mole of liquid turns into gas. Evaporation process requiring energy input for phase change.

Flashcard 7: State the enthalpy change for the formation of one mole of carbon dioxide from carbon and oxygen.

Answer: $\Delta H_f^\circ = -393.5$ kJ/mol. Standard formation enthalpy for carbon dioxide from elements.

Flashcard 8: Find the enthalpy change for the reaction given $H_{products} = 100$ kJ and $H_{reactants} = 150$ kJ.

Answer: $\Delta H = -50$ kJ. Using $\Delta H = H_{products} - H_{reactants} = 100 - 150$.

Flashcard 9: What does the symbol $\Delta H_{rxn}$ represent?

Answer: It represents the enthalpy change for a chemical reaction. Standard notation for reaction enthalpy under specified conditions.

Flashcard 10: What is the relationship between $\Delta H$ and $q$ at constant pressure?

Answer: $\Delta H = q$ at constant pressure. Direct equivalence when pressure remains constant throughout.

Flashcard 11: Calculate the enthalpy change for a reaction if $q = 250$ J and $n = 0.5$ mol.

Answer: $\Delta H = 500$ J/mol. Using $\Delta H = \frac{q}{n} = \frac{250}{0.5}$.

Flashcard 12: What is meant by 'enthalpy of combustion'?

Answer: It is the enthalpy change when one mole of a substance burns completely in oxygen. Complete oxidation reaction with oxygen as the oxidizing agent.

Flashcard 13: Identify the enthalpy change for the evaporation of water.

Answer: $\Delta H_{vap} = 40.7$ kJ/mol. Energy required for liquid-to-gas phase transition.

Flashcard 14: Define the term 'standard state' in the context of enthalpy.

Answer: It is the physical state of a substance at 1 atm and 25°C. Reference conditions for comparing thermodynamic properties.

Flashcard 15: What is the enthalpy of fusion?

Answer: It is the enthalpy change when one mole of solid turns into liquid. Melting process requiring energy input for phase change.

Flashcard 16: Which type of reaction absorbs heat from the surroundings?

Answer: Endothermic reactions absorb heat. Positive $\Delta H$ indicates heat absorption from surroundings.

Flashcard 17: What is the enthalpy of neutralization?

Answer: It is the enthalpy change when an acid and a base react to form water. Acid-base reaction forming water as the primary product.

Flashcard 18: What is the definition of enthalpy (H)?

Answer: Enthalpy (H) is the heat content of a system at constant pressure. Represents total internal energy plus pressure-volume work.

Flashcard 19: Identify the components in the enthalpy change equation $\Delta H = q_p$.

Answer: $q_p$ represents the heat absorbed or released at constant pressure. Heat transfer equals enthalpy change at constant pressure.

Flashcard 20: Calculate the $\Delta H$ for a reaction using Hess's Law given multiple reactions.

Answer: Add individual $\Delta H$ values to find total $\Delta H$. Sum intermediate steps to find overall enthalpy change.

Flashcard 21: Calculate $\Delta H$ using calorimetry data for a reaction.

Answer: Use $q = mc\Delta T$ and $\Delta H = \frac{q}{n}$, where $n$ is moles. Combine heat capacity data with molar quantities.

Flashcard 22: What is the significance of a large negative $\Delta H$ value?

Answer: It indicates a strongly exothermic reaction. Large energy release indicates highly favorable reaction.

Flashcard 23: What does a negative $\Delta H$ signify about a reaction?

Answer: A negative $\Delta H$ indicates an exothermic reaction. Heat is released to the surroundings during the reaction.

Flashcard 24: What is the enthalpy change for the conversion of diamond to graphite?

Answer: $\Delta H = -1.9$ kJ/mol. Slightly exothermic carbon allotrope transformation.

Flashcard 25: What is the significance of enthalpy in chemical reactions?

Answer: Enthalpy helps predict the heat exchange and spontaneity of reactions. Determines energy requirements and reaction feasibility.

Flashcard 26: What is the enthalpy change when 1 mol of water forms from hydrogen and oxygen?

Answer: $\Delta H_f^\circ = -285.8$ kJ/mol. Standard formation enthalpy for liquid water from elements.

Flashcard 27: What is the enthalpy change when one mole of ice melts to water at 0°C?

Answer: $\Delta H_{fus} = 6.01$ kJ/mol. Energy required for solid-to-liquid phase transition.

Flashcard 28: Identify the enthalpy change for the evaporation of water.

Answer: $\Delta H_{vap} = 40.7$ kJ/mol. Energy required for liquid-to-gas phase transition.

Flashcard 29: What is the enthalpy change for the conversion of diamond to graphite?

Answer: $\Delta H = -1.9$ kJ/mol. Slightly exothermic carbon allotrope transformation.

Flashcard 30: Calculate the enthalpy change for a reaction if $q = 250$ J and $n = 0.5$ mol.

Answer: $\Delta H = 500$ J/mol. Using $\Delta H = \frac{q}{n} = \frac{250}{0.5}$.