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# Chapter 6

### Thermochemistry (Test 3)

thermodynamics the study of energy and its transformations
thermochemistry the study of the relationship between chemical reactions and energy
energy the capacity to do work
heat the flow of energy caused by a temperature difference
work the result of a force acting through a distance
What is the equation for work involving force and distance? w = F times d
What is the equation for work involving pressure and volume? w = - P (delta V)
kinetic energy the energy associated with the motion of an object
What is the equation for kinetic energy? Ek = (1/2)(m)(V^2)
potential energy stored energy; energy due to position or composition (examples: chemical energy)
thermal energy energy associated with the temperature of a substance
chemical energy energy associated with the relative positions of electrons and nuclei in atoms and molecules
system the part of the universe being studied
surroundings everything else in the universe
internal energy of the system (E) the sum total of all of the kinetic and potential energies of every particle in the system; unknowable
state function a function that is independent of the history or path followed
What are some examples of state functions? temperature, volume of a gas, location, molarity, internal energy, enthalpy, and change in any of these.
What is one joule equal to? 1 (kg * m^(2))/(s^(2))
What is the First Law of Thermodynamics? the law of conservation of energy; the total energy of the universe is constant.
What is the equation that expresses the First Law of Thermodynamics? delta E = q + w, where delta E is the change in internal energy, q is heat, and w is work.
How do you determine if the sign of q is positive or negative? q is positive if heat flows from the surroundings to the system; q is negative if heat flows from the system to the surroundings. w is positive if the surroundings do work on the system; w is negative if the system does work on the surroundings.
calorimetry measuring heat flow
calorimeter an instrument used for measuring heat flow
bomb calorimeter a constant volume calorimeter delta E = q sub v, where q sub v is heat flow under constant volume
coffee-cup calorimeter a constant pressure calorimeter delta H = q sub p, where q sub p is heat flow under constant pressure
heat capacity the amount of heat required to raise the temperature of a substance by 1 degree Celsius
specific heat capacity the amount of heat required to raise the temperature of 1 g of a substance by 1 degree Celsius
What is the equation for heat? q =(m)(c)(delta T)
When a problem involves two substances, how do you determine heat? -q = q
In a bomb calorimeter (constant volume), what equation is used? delta E = q sub v
How many joules are equal to 1 liter*atmosphere? 101.3 J = 1 L*atm
delta H enthalpy change; heat flow under constant pressure
An endothermic reaction has which sign of delta H? positive
An exothermic reaction has which sign of delta H? negative
The stoichiometric coefficients in a thermochemical reaction refer to what? the number of moles of reactants and products
A reversed reaction has what effect on the delta H of that reaction? changes the sign
The enthalpy change, delta H, is for what? the specified number of moles
What is Hess's Law? the total enthalpy change (delta H) for a process is the same regardless of whether the process occurs in one step or many steps
What is a formation reaction? forming one mole of a substance from its elements in their most stable forms
Any element in its most stable form has what enthalpy of formation? 0
To find delta H of a reaction using delta H of formations, always do what? delta H formation of products - delta H formation of reactants
Created by: 2nenogirl