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Chapter 7: Energy, rates, and equilibrium
Terms in this set (29)
The amount of energy that must be supplied to break a a bond and separate the atoms in an isolated gaseous molecule. Bond dissociation energies are a measure of the strength of a covalent bond
What is bond dissociation energy?
A process or reaction that absorbs heat - POSITIVE value for delta H
What is an endothermic reaction?
Process or reaction that releases heat - NEGATIVE value for delta H
What is an exothermic reaction?
Abbreviated by letter H - is a measure of energy in the form of heat
What is Enthalpy?
Energy can be neither created nor destroyed in any physical or chemical change
What is law of conservation of energy?
Represented by delta H - different between the energy absorbed in breaking bonds and that released in forming bonds
What is heat of reaction?
Chemical equations that include information about energy changes
What is a thermochemical equation?
A process or reaction that, once started, proceeds on its own without any external influence. A spontagneous process is one in which free energy is released - delta G is NEGATIVE
What is a spontaneous reaction?
Opposite of spontaneous reaction, takes place only in the prescence of a continuous external influence and is one in which free energy is added - delta G is POSITIVE
What is a non spontaneous reaction?
Value of delta G
What determines spontaneity?
If G is negative, free energy is released; the process is exergonic
What happens if delta G is negative?
If G is positive, free energy is added; process is endergonic
What happens if delta G is positive?
The amount of molecular disorder in a system. Abbreviated with the letter S
What is Entropy?
S is positive when disorder increases
What happens when S is positive in entropy?
S is negative when disorder decreases
What happens when S is negative in entropy?
Measure of how rapidly a chemical reaction takes place
What is reaction rate?
Reactant particle must collide, some chemical bonds have to break
What must happen for a chemical reaction to occur?
The amount of energy the colliding particles must have for productive collisions to occur. The size of activation energy determines the reaction rate, or how fast the reaction occurs
What is activation energy?
The lower the activation energy, the greater the number of productive collision in a given amount of time, and the faster the reaction
What happens if there is a lower activation energy?
The higher the activation energy, the lower the number of productive collisions, and the slower the reaction
What happens if there is a higher activation energy?
Addition of heat increases rate of reaction
How can heat affect the reaction speed?
A reaction that can go in either direction, from products to reactant os reactants to products. This situation that exists when the reactants and products are approximately equal stability.
What is a reversible reaction?
What represents the equilibrium constant?
Varies with temperature
When does the value of K vary?
Indicates the position of a reaction at equilibrium
What does the value of K indicate?
Favors forward reactions
What happens if the K value is larger than 1?
Favors backward reactions
What happens if the K value is smaller than 1?
Significant amounts of reactants and products are present at equilibrium
What happens when K is close to 1?
When a stress is applied to a system at equilibrium, the equilibrium shifts to relive the stress. The stress can be any change in concentration, pressure, volume, or temperate that disturbs original equilibrium
What is Le Chatelier's principle?
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