Thermodynamics Overview

<p>Chemical reactions either require or release energy. (B)</p> Signup and view all the answers

<p>Potential energy can be stored due to an object's position. (B)</p> Signup and view all the answers

<p>The total energy remains constant. (C)</p> Signup and view all the answers

<p>Kinetic energy is proportional to the square of the velocity. (D)</p> Signup and view all the answers

<p>Ek = ½ mv² (B)</p> Signup and view all the answers

<p>The internal energy decreases because work is done by the system. (A)</p> Signup and view all the answers

<p>Work done by the system results in energy loss. (A)</p> Signup and view all the answers

<p>ΔU = q + w (B)</p> Signup and view all the answers

<p>Work is done on the system. (B)</p> Signup and view all the answers

<p>-1 mole (C)</p> Signup and view all the answers

<p>Pressure is inversely proportional to volume at constant temperature. (C)</p> Signup and view all the answers

<p>Internal energy decreases due to work done by the system. (D)</p> Signup and view all the answers

<p>w is the work done by the external pressure on the system. (B)</p> Signup and view all the answers

<p>The process is endothermic. (C)</p> Signup and view all the answers

<p>Adiabatic process. (D)</p> Signup and view all the answers

<p>The enthalpy change of the reaction. (A)</p> Signup and view all the answers

<p>DU equals q. (D)</p> Signup and view all the answers

<p>The reverse of an endothermic reaction is exothermic. (C)</p> Signup and view all the answers

<p>Temperature remains constant. (C)</p> Signup and view all the answers

<p>By taking the sum of products' enthalpy minus reactants' enthalpy. (B)</p> Signup and view all the answers

<p>Reactions in systems without gas involvement. (D)</p> Signup and view all the answers

<p>They indicate the physical states of the reactants and products. (B)</p> Signup and view all the answers

<p>Denoted by the superscript ᶿ or 0. (D)</p> Signup and view all the answers

<p>The energy needed to form a substance from its elements in their reference states. (D)</p> Signup and view all the answers

<p>92.2 kJ (A)</p> Signup and view all the answers

<p>-18.4 kJ (D)</p> Signup and view all the answers

<p>1 bar pressure, 25 oC (298 K), and 1 M concentration. (A)</p> Signup and view all the answers

<p>-2043 kJ (A)</p> Signup and view all the answers

<p>It varies between standard enthalpy and actual reaction conditions. (B)</p> Signup and view all the answers

<p>All routes lead to the same value for a state function. (A)</p> Signup and view all the answers

<p>N2H4(g) + H2(g) → 2NH3(g) (A), N2(g) + 2H2(g) → N2H4(g) (B)</p> Signup and view all the answers

<p>It is the negative of the enthalpy change of the forward reaction. (D)</p> Signup and view all the answers

<p>C4H10(g) + 6½ O2(g) → 4 CO2(g) + 5 H2O(l) (B)</p> Signup and view all the answers

<p>They provide a standardized method to calculate changes without experiments. (B)</p> Signup and view all the answers

<p>-74.7 kJ/mol (A)</p> Signup and view all the answers

<p>2H2(g) + O2(g) → 2H2O(l) (A)</p> Signup and view all the answers

<p>State functions are only applicable to gaseous reactions. (C)</p> Signup and view all the answers

<p>Energy required to convert a solid ionic compound into gas. (D)</p> Signup and view all the answers

<p>Change in enthalpy of formation. (A)</p> Signup and view all the answers

<p>First ionization energy of sodium. (D)</p> Signup and view all the answers

<p>Energy needed to form Cl2 from gaseous chlorine atoms. (C)</p> Signup and view all the answers

<p>Sublimation energy, ionization energy, and bond dissociation energy. (C)</p> Signup and view all the answers

<p>Ionization of sodium to form Na+(g). (A)</p> Signup and view all the answers

<p>Electron affinity of chlorine. (C)</p> Signup and view all the answers

<p>-411 kJ/mol. (D)</p> Signup and view all the answers

The capacity to do work or supply heat.

Energy of motion.

Stored energy.

Energy cannot be created or destroyed, only converted.

Kinetic energy of molecular motion.

Thermal energy transferred due to a temperature difference.

Potential energy stored in chemical bonds.

Total energy of an isolated system remains constant.

Work done by a system due to changes in its volume, often caused by gas expansion or compression.

Equal volumes of gases at the same temperature and pressure contain the same number of molecules.

A relationship between pressure, volume, temperature, and the number of moles of an ideal gas: PV = nRT.

Work done by a system on its surroundings when its volume increases. This is an example of negative work.

Work done on a system by its surroundings when its volume decreases. This is an example of positive work.

The difference between the moles of gaseous products and the moles of gaseous reactants in a chemical reaction.

The total energy of a system, including kinetic and potential energies of its molecules.

The heat content of a system at constant pressure. It is the internal energy plus the product of pressure and volume.

The heat transferred (q) is equal to the change in internal energy (DU) plus the work done by the system (PDV).

At constant volume, the heat transferred (qv) is equal to the change in internal energy (DU).

At constant pressure, the heat transferred (qp) is equal to the enthalpy change (DH).

The heat change at constant pressure, also called the heat of reaction. It is the difference in enthalpy between products and reactants.

A process that absorbs heat from the surroundings, resulting in a positive DH.

A process that releases heat to the surroundings, resulting in a negative DH.

A balanced chemical equation that includes the enthalpy change of the reaction (DH).

The enthalpy change for a reaction when all reactants and products are in their standard states (25°C, 1 atm, 1 M for solutions).

The most stable physical state of a substance at 25°C, 1 atm pressure, and 1 M concentration for solutions.

The enthalpy change for a specific reaction, regardless of the specific conditions.

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states.

The most stable form of an element under standard conditions (1 atm, 298 K).

The opposite of a forward reaction, with the products becoming reactants and vice versa.

Endothermic reactions absorb heat from the surroundings (DH is positive), while exothermic reactions release heat (DH is negative).

The energy released when one mole of an ionic compound is formed from its gaseous ions.

A thermodynamic cycle used to calculate the lattice energy of an ionic compound by relating it to other enthalpy changes.

To determine the lattice energy of an ionic compound by calculating the enthalpy changes of each step in the cycle.

The Born-Haber cycle is a specific application of Hess's Law, where the enthalpy changes of a series of reactions are used to calculate the enthalpy change of an overall reaction.

The steps include sublimation of the metal, dissociation of the nonmetal, ionization of the metal, electron affinity of the nonmetal, and formation of the ionic compound.

The process of a solid directly changing into a gas without becoming a liquid.

The energy change that occurs when an electron is added to a gaseous atom.

A property of a system whose value depends only on the current state of the system, not on the path taken to reach that state. For example, the enthalpy change of a reaction is a state function because it only depends on the initial and final states of the reactants and products, not on the specific steps involved.

The energy required to remove an electron from a gaseous atom.

The total enthalpy change for a reaction is the sum of the enthalpy changes for each step in the reaction. This means that the enthalpy change of a reaction can be calculated by adding the enthalpy changes for a series of reactions that add up to the overall reaction.

The enthalpy change when one mole of a compound is formed from its elements in their standard states.

Use Hess's Law to calculate the change in enthalpy for a reaction by manipulating known enthalpy changes of other reactions. Be sure to reverse the signs of changes if a reaction is reversed, and multiply changes by the stoichiometric coefficients if a reaction is multiplied.

Use the enthalpy of changes for each of the reactants and products to calculate the enthalpy change for the entire reaction. The equation is: ΔH°rxn = ΣΔH°f (products) – ΣΔH°f (reactants).

The Haber process produces ammonia (NH3) from nitrogen gas (N2) and hydrogen gas (H2).

Hess's Law is a useful tool for calculating enthalpy changes, which are often difficult or impossible to measure directly. It allows scientists to determine the enthalpy change for a reaction by using known enthalpy changes for other reactions.