TOPIC 11- THERMOCHEMISTRY Flashcards
is the capacity to do work or produce heat.
Energy
states that energy can be
converted to another form but can be neither created nor destroyed.
Law of Conservation of Energy
The total energy content of the universe is
Constant
What are the classifications of energy?
- Potential Energy
- Kinetic Energy
is due to position or composition and can also be a
result of attractive and repulsive forces.
Potential Energy
is due to the motion of an object and depends on the
mass and velocity of the object.
Kinetic Energy
is the part of the universe that is the current point of focus.
system
include everything else in the universe.
Surroundings
are reactions in which heat is expended and
flows out of the system.
negative
Exothermic Reactions
are reactions in which heat is absorbed and
flows into the system.
Endothermic Reactions
If two reactants at the same temperature are mixed and the resulting
solution gets warmer, this means the reaction taking place
exothermic
endothermic reaction ____ the solution.
cools
What are the types of systems?
- Open System
- Closed System
- Isolated System
allows both matter and energy (heat) to be exchanged
between the system and surrounding.
Open System
only allows energy (heat) to be exchanged between
the system and surrounding.
Closed System
does not allow both matter and energy (heat) to be
exchanged between the system and surrounding.**
Isolated System
of a system is the sum of the kinetic and potential
energies of all “particles” in the system.
can be changed by a flow of work,
heat, or both.
Internal Energy (E)
is often called the first law of
thermodynamics and proposes that the energy of the universe is
constant.
Law of Conservation of Energy
What are the two ways which a system can change its internal energy?
- Losing some energy to the sorroundings
- Gaining some energy to the surroundings
When losing some energy to the surroundings, what happens to the △E and energy?
△E is negative and energy leaves the system. Therefore, it is exothermic.
When gaining some energy from the surroundings, what happens to the △E and energy?
△E is positive and energy enters the system. Therefore, it is endothermic.
What are the possibilities when energy transfers as heat only?
- heat flows out of the system
- heat flows into the system
What are the possibilities when energy transfer as work only?
- work done by the system (exothermic)
- work done by the surrounding (endothermic)
When a system gains energy, the surrounding loses the same magnitude of
energy and vice versa.
First Law of Thermodynamics
It is expressed using the letter H and is a state function.
enthalpy
is a property of a system that depends on the state of a
system only, such as internal energy, pressure, and volume.
State function
Enthalpy change is affected by the?
states of product and reactants
The change in enthalpy at constant pressure is equal to the _______________ at that same
pressure (only pressure-volume work is allowed).
heat
The _________________ is also equal to the difference of the enthalpy of
products and reactants.
change in enthalpy
Δ𝐻 is ——- when the enthalpy of products is greater than that of reactants.
positive
Δ𝐻 is _____________ when the enthalpy of products is lesser than that of reactants.
negative
does not depend on the
pathway between two states.
change in enthalpy
It is the science of measuring heat.
calorimetry
measures the heat associated with chemical reactions.
calorimeter
is the energy required to raise the temperature
of one gram of substance by one degree Celsius.
Specific Heat Capacity
is like specific heat capacity but without the gram units.
Heat Capacity
is the energy required to raise the temperature of
one mole of substance by one degree Celsius.
Molar Heat Capacity
If a substance has a higher Δ𝑇 than another, it means it has a __________
specific heat.
smaller
Metals require comparatively ___________ to increase their
temperature by one degree.
lesser energy
is often used to measure the heat transferred
in processes open to the atmosphere.
coffee-cup calorimeter
Determines changes in enthalpy for reactions that occur in solution.
Constant-Pressure Calorimetry
In a constant-volume process, the change in volume ΔV is equal to zero,
meaning that work is also zero.
Constant-Volume Calorimetry
The Δ𝐻 of an overall reaction is equal to the sum of the individual
enthalpy change of each step.
Hess’s Law
If a reaction is reversed, the sign of Δ𝐻 becomes the _________.
opposite
is the change in enthalpy accompanying the formation of one mole of a compound from its
elements with all substances in their standard states.
standard ethalpy of formation
Positive Δ𝐻 exhibits an?
Endthermic Reaction
Negative Δ𝐻 exhibits an
Exothermic Reaction
is a precisely defined reference state.
standard state
In standard states, _________ are:
* a pressure of exactly 1 atm in gases
* pure liquid or solid for condensed pure substances
* a concentration of exactly 1 M for substances in a solution
compounds
In standard states, _________ is a form in which the elements exist under conditions of 1 atmosphere and 25°C
elements
_____ in their standard states are not included in the calculations
Elements
