Chapter 5 Flashcards
What is the equation to find Electrostatic Potential energy?
Eel= kQ1Q2/d
What is zero electrostatic potential energy?
as the potential energy at infinite speration of the charged particles.
When Q1 and Q2 have the same sign what happens to the particles?
they repel each other and a repulsive forces pushes them apart
How do you bring two postiviely charged objects closer?
you have to do work to overcome the repulsive force that exists between the two
What does the potential energy do as Electrostatic energy is postive?
deceares
What does distance do as potential energy decreases?
increase
What happens when Q1 and Q2 have opposite signs?
the particles attract each other and an attractive force pulls them toward each other
When is Electrostatic potential energy negative?
when the charges have opposite signs
What does the potential energy do as Electrostatic enrgy is negative
increases
What does distance do as potential energy increases?
decrease
How is energy released?
chemical bonds are formed
How is energy consumed?
chemical bonds are broken
What is the first law of thermodynamics?
energy can be converted from one from to another, but it is neither created nor destroyed
What is the equation to find internal energy?∆E
∆E= q+w
What is the system?
the portion of the unvierse that we single out for study
What is the surroundings?
everything that lies outside teh system that we study
What is an open system?
one in which matter and energy can be exchanged with the surroundings
Ex:an uncovered pot of boiling water on a stove
What is a closed system?
exchange energy but not matter with its surroundings
Ex:a mixture of hydrogen gas, and oxygen gas in a cylinder fitted with a piston
What is an isolated system?
neither energy nor matter can be exchanged with the surroundings
Ex: an insulated thermos containing hot coffee
What is internal energy?
the sum of all the kinetic and potnetial energies of the componetns of the system
What does a -∆E mean?
lost energy to its surroundings
What does a +∆E mean?
gained energy from its surroundings
What causes ther maginuted of internal energy(∆E) to change?
the adding and removing of heat or as work is done on or by the system
When heat is added to a system do the ∆E increase or decrease?
increases
When work is done on a system does ∆E increase or decrease?
increases
When does q or heat have a postive value?
when heat is transferred to the system from the surroundings
When does w(work) have a postive value?
when work is done on the system by the surroundings
When heat is lost by the system does ∆E increase or decrease?
decrease
When work is done by the system on the surroundings does ∆E increase or decrease?
decrease
When does w(work) have a negative value?
when work is done by the system on the surroundings
When does q(heat) have a negative value?
heat lost by the system to the surroiundings
When is a process endothermic?
system absorbs heat from its surroundings
When is a process exothermic?
system loses heat
What influences internal energy of a system?
temperature and pressure
What is a state function?
a property of a system that is determined by its state or condition and not by how it got to that state
What are examples of state functions?
Tempature, pressure, composition
What kind of a function is ∆E?
state function
What kind of a function is q?
path function
What kind of function is w?
path function
What is ∆H?(change in enthalpy)
a reaction that occurs at constant pressure is the heat evolved or absorbed in the reaction
How do you find enthalpy?(H)
E+PV
What is pressure-volume work?
work perfomed by exapnsion of a gas against a resisting pressure
What is the equation for volume-pressure work?
w=-P∆V
When is pressure volume work positive?
when ∆V is negative, work done on the system by surroundings
when is the pressure volume work negative?
∆V is positive, system does work on teh surroundings
How many J is in 1L-atm?
101.3J
What is the equation for ∆H(change in enthalpy)?
∆H= ∆E+P∆V
What is ∆H= to?
q(heat of system at constant pressure)
when ∆H(change in enthalpy) is positive what is q?
the system has gained heat from the surroundings so also postivie
When ∆H( change in enthalpy) is negative what is q(heat)?
the system released heat to the surroundings(-)
When ∆H is positive and q is postive is endothermic or exothermic?
endothermic
When ∆H is negative and q is negative is it endothermic or exothermic?
exothermic
Is ∆H a state or path function?
state function
What is the ∆H for a chemical reaction?
∆H=Hproducts- Hreactants
What is enthalpy of reaction?
the enthalpy change associated with a chemical reaction
How is enthalpy of reaction written?
∆Hrxn
Is enthalpy a extensive or intensive proerpty?
extensive property
What is ∆H proportional to?
the amount of reactant consumed in the process
What happens to the ∆H when you reverse the reaction?
the signs flip
What does the ∆Hrxn depend on?
states of the reactants and products
How to find heat(q) when given g of a reactant and the chemcial formula and the ∆H
Convert g to moles use the moles in chemical equation times the ∆H
What is calorimetry?
the experimental measurement of heat produced in chemical and physical processes
What is caloriemter?
an apparatus that measrues the heat released or absorbed in a chemical or physical process
What is heat capacity?
the quantity of heat required to raise the temperature of a sample of matter
What is molar heat capactiy?
the heat required to raise the temperature of one mole of a substance
What is specifc heat?
the heat capacity of 1g of a substance the heat required to raise the temperature of 1g of a substance by 1 degree celsisus
How can you find specifc heat(Cs)?
q(heat)/m x ∆T
What is the units of Cs(specific heat)?
J/g-K
How do you find q(heat)?
q=Cs(specific heat) x m x ∆ T
What is constant-pressure calorimetry?
monitoring the temp of the solution, we are seeing the flow of heat between teh system and the surroundings
When does the tempature rise in constant pressure calorimetry?
heat is lost by the reaction and gained by the water in the solution(exothermic reaction)
When is tempature decreased?
heat is gained by the reaction and lost by the water in teh solution
What is the heat of the solution=?(qsoln)
-heat of reaction(-qrxn)
When ∆T is positive what is qrxn?
negative
What is a bomb calorimeter?
a device for measuring the heat evolved in the combustion of a substance under constant volume conditions
What is the qrxn for a bomb calorimeter?
qrxn=-Ccal x ∆T
What is Hess’s law?
if a reaction is carried out in a seried of stpes, ∆H for the overall reaction equals the sum of the enthalpy changes for the steps
What is enthalpy of formation?
the enthalpy change that accompanies the formation of a substance from the most stable forms of its component elements
How do you find enthalpy of formation? (∆H˚f)
wanting to find the a compound of something by getting one mole of it
How to find enthalpy formation of a reaction?(∆H˚rxn )
∑n∆H˚f(products)-∑m∆H˚f(reactants)
What is the ∆H˚rxn for decomposition?
the reverse of the formation reaction
What is bond enthalpy?
the enthalpy change, ∆H required to break a particular bond when the substance is in the gas phase
How to find ∆Hrxn(for bonds)?
∑(bond enthalpies of bonds broken)-∑Bond enthalpies of bonds formed)
