Thermochemistry Flashcard

Thermochemistry
The study of energy changes that occur during chemical reactions and changes in states.
Chemical Potential Energy
Engergy strored in chemical bonds
Heat
(represented by q) is energy transfers from one object to another because of a temperature differance between them.
Heat
(represented by q) is energy transfers from one object to another because of a temperature differance between them. *Key Concept: heat always flows from a warmer object to a cooler object*
System
The part of the universe on which you focus your attention.
Surroundings
Everything else in the universe not including the system. (The immediate vicinity of the systems surroundings in terms of thermochemistry)
Law of Conservation of Energy
In any chemical or physical change, energy is neither created nor destroyed. If the energy of a system decreases, then the energy of the surroundings increases so the total energy remains the same.
Endothermic Process
Absorbs heat from the surroundings *Key Concept: In an endothermic reaction, the surrounding cools down (measured temerature)*
Exothermic Process
One that releases heat to its surroundings. *Key Concept: the system looses heat, so the surroundings (measured temperature) heats up*
Calorie
the quantity of heat needed to raise the temperature of pur water 1*C. One dietary Calorie equals 1000 calories, or one kilocalorie
Joule
the SI unit of energy. One joule raises the temperature of one gram of pure water .2390*C
Heat Capacity
The amount of heat needed to increase the temprature of an object exactly one degree celcius. *Key Concept: the heat capacity of an object depends on the mass and chemical composition*
Specific Heat
the amount of heat it takes to raise thte temperature of 1 gram of a substance 1*C. See table 17.1 on page 508.
Calculation for specific heat of a substance
specific heat (C)= heat (q) in joules / mass (m) in grams * change in temperature (degrees Celcius)
Calorimetry
the precise measurement of the heat flow into or out of a system. *Key Concept: In calorimetry, the heat released from a system is equal to the heat absorbed by the surroundings. Conversely, the heat absorbed by a system is equal to the heat released by the surroundings.*
Calorimeter
the insulated device used to measure the absorption or release of heat in a chemical or physical process.
Enthalpy (H)
The heat content of the system at constant pressure.
q=change in H
enthalpy of a reaction
q=MC(delta)T
Thermochemical Equation
A chemical equation including enthalpy of change. *Key Concept: In a chemical equation, the enthalpy of change for the reaction can be written as either a reactant of a product.*
Heat of Reaction
the enthalpy change of a reaction exactly as it is written.
Heat of Combustion
The heat of reaction for the complete burning of one mole of a substance.
Molar Heat of Fusion
The amount of energy as heat absorbed by one mole of a solid substance as it melts to a liquid at constant temperature. *Key Concept: The quantity of heat as energy absorbed by a melting solid is exactly the same as the quantity of heat released when the liquid solidifies.*
Molar Heat of Solidification
The amount of energy as heat lost when one mole of a liquid solidifies at constant temperature. *Key Concept: The quantity of heat as energy absorbed by a melting solid is exactly the same as the quantity of heat released when the liquid solidifies.*
Molar Heat of Vaporization
The amount of energy as heat needed to vaporize one mole of a given liquid. (See Table 17.3)*Key Concept: The quantity of heat absorbed by a vaporizing liquid is exactly the same as the quantity of the energy as heat released when it condenses.*
Molar Heat of Condensation
The amount of energy as heat released when one mole of a gas condenses at its normal boiling point. *Key Concept: The quantity of heat absorbed by a vaporizing liquid is exactly the same as the quantity of the energy as heat released when it condenses.*
Molar Heat of a Solution
The enthalpy change caused by thedissolution of one mole of a substance. *Key Concept: During the formaton of a solution, heat is either released or absorbed.*
Hess’s Law of Heat Summation
If you can add together two or more thermochemical equation to give a final equation, then you can also add the energy as heat of the reactions to come up with the heat of the final reaction. *Key Concept: Hess’s Law allows you to determine the heat of a reaction indirectly.*
Standard Heat of Formation
The change in enthalpy that accompanies the formation of one mole of a compound from its elements in their standard states at 25*C and 101.3 kPa *Key Concept: For a reaction that occurs at standard conditions, you can calculate the heat of reaction by using standard heat of formation ((Delta)Standard heat of reaction= (delta)standard heat of formation products-(delta)standard heat of formation reactants)* (See Table 17.4)

Get instant access to
all materials

Become a Member