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60 Cards in this Set

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What is a system?
The particular part of the universe being studied
What is everything outside the system considered?
It is considered the surroundings or environment
What three things can a system be?
It can be isolated, closed, or open
What is an isolated system?
It cannot exchange energy or matter with the surroundings
What is a closed system?
It can exchange energy but not matter with the surroundings
What is an open system?
It can exchange energy and matter with the surroundings
When does a system undergo a process?
It undergoes a process when one or more of its properties change
What is a process associated with?
It is associated with a change of state
When does an isothermal process occur?
It occurs when the temperature of the system remains constant
When does an adiabatic process occur?
When no heat exchange occurs
When does an isobaric process occur?
It occurs when the pressure of the system remains constant
What is heat?
It is a form of energy which can easily transfer to or from a system, the result of a temperature difference between the system and its surroundings
What is heat absorbed by a system considered?
It is considered positive
What is heat lost by a system considered?
It is considered negative
What are reactions called that absorb heat energy?
They are endothermic
What are those that release heat energy?
They are exothermic
What is heat measured in?
It is measured in calories or Joules and more commonly in kcal or kJ
What is the conversion for calories to Joules?
1 calorie is equal to 4.184 Joules
What is the heat (q) absorbed or released in a given process calculated from?
It is calculated from the equation q = mct
What occurs in constant-volume calorimetry?
The volume of the container holding the reacting mixture does not change during the course of the reaction
What are state functions?
They depend only on the initial and final states of the system, and not on the path of the change
What are the state functions?
Pressure, temperature, volume, enthalpy (H), entropy (S), free energy (G) and internal energy (E or U)
What is the set for normal conditions?
25C and 1atm
What is it used for?
It is normally used to measure enthalpy, entropy, and free energy of a reaction
What is a substance called that is in its most stable form under standard conditions?
It is in its standard state
What are the changes in enthalpy, entropy, and free energy called when they occur under standard conditions?
They are called standard enthalpy, standard entropy, and standard free energy
What do chemists use the term enthalpy (H) for?
They use it to express heat changes at constant pressure
What is the change in enthalpy equal to?
It is equal to the heat absorbed or evolved by the system at constant pressure
To find the enthalpy change of a reaction, what do you do?
You subtract the enthalpy of the reactants from the enthalpy of the products
What does a positive H correspond to?
It corresponds to an endothermic process
What does a negative H correspond to?
It corresponds to an exothermic process
What is the enthalpy of formation of a compound?
It is the enthalpy change that would occur if one mole of a compound were formed directly from its elements in their standard states
What is the standard heat of reaction?
It is the hypothetical enthalpy change that would occur if the reaction were carried out under standard conditions, ie when reactants in their standard states are converted to products in their standard states at 298K
What does Hess’s law state?
Hess’s law states that enthalpies of reactions are additive
What are the heats of reaction related to?
They are related to changes in energy associated with the break-down and formation of chemical bonds
What is bond energy, or bond dissociation energy?
It is the average of the energy required to break a particular type of bond in one mole of gaseous molecules
What is entropy (S)?
It is the measure of the disorder, or randomness, of a system
What are the units of entropy?
They are energy/temperature, commonly J/K or call/K
How does order relate to entropy?
The greater the order in a system, the lower the entropy
Do solids have a higher or lower entropy than a gas?
They have a lower entropy than a gas because individual molecules in the gaseous state are moving randomly, while individual molecules in a solid are constrained in place
What does the second law of thermodynamics state?
It states that all spontaneous processes proceed such that the entropy of the system plus its surroundings increases:
When does a system reach its maximum entropy?
It reaches it at equilibrium
What does Gibbs Free Energy do?
It combines the two factors which affect the spontaneity of a reaction
What are the two?
Changes in enthalpy, and changes in entropy
What does the change in free energy of a system represent?
It represents the maximum amount of energy released by a process, occurring at constant temperature and pressure
What is the equation?
G = H – TS
What does it mean if G is negative?
The reaction is spontaneous
What does it mean if G is positive?
The reaction is nonspontaneous
What does it mean if G is zero?
The system is at equilibrium
If enthalpy is negative and entropy is positive, is the reaction spontaneous, when?
It is spontaneous at all temperatures
If the enthalpy is positive and the entropy is negative, is the reaction spontaneous, when?
It is nonspontaneous at all temperatures
If the enthalpy and entropy are both positive, is the reaction spontaneous, when?
It is spontaneous only at high temperatures
If the enthalpy and entropy are both negative, is the reaction spontaneous, when?
It is spontaneous only at low temperatures
What does the rate of a reaction depend upon?
It depends upon the activation energy
Does it depend on G?
It does not depend on G
What is the standard free energy
It is defined as the G of a process occurring at 25C and 1atm pressure, and for which the concentrations of any solutions involved are 1 M
What is the standard free energy of formation?
It is the free-energy change that occurs when 1 mol of a compound in its standard state is formed from its elements in their standard states under standard conditions
What is the standard free energy of formation of any element in its most stable form?
Zero
What is the standard free energy of reaction?
It is the free energy change that occurs when that reaction is carried out under standard state conditions, i.e., when the reactants in their standard states are converted to the products in their standard states, at standard conditions of T and P
What is the reaction quotient (Q)?
It is the products raised to their amounts divided by the reactants raised to their amounts