Thermochemistry Review Flashcards
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44 Terms
Endothermic Process
A process where heat is absorbed from the surroundings.
Exothermic Process
A process where heat is released to the surroundings.
Exothermic process example
Burning wood
Positive ΔH
Indicates an endothermic reaction.
ΔH meaning
The heat change at constant pressure.
Increasing reactant concentration (Le Châtelier's principle)
Shift equilibrium toward products.
Increasing temperature in an exothermic reaction at equilibrium
Shift the reaction toward reactants.
Highest activation energy
A slow reaction.
Le Châtelier's principle applies to
Systems at equilibrium.
Catalyst Action
Catalyst provides an alternate pathway with lower activation energy.
Endothermic Reaction
A reaction that absorbs heat from the surroundings; example: melting ice.
Exothermic Reaction
A reaction that releases heat to the surroundings; example: burning wood.
ΔH meaning
ΔH tells us the heat change during a reaction at constant pressure (enthalpy change).
Temperature effect on reaction rate
Temperature increases reaction rate because it increases the kinetic energy of molecules, leading to more frequent and forceful collisions.
Two factors that increase reaction rate
Increasing temperature and adding a catalyst.
Adding product to a system at equilibrium
The system will shift toward the reactants to restore equilibrium.
SI unit for energy
Joule (J) and calorie (cal).
Difference between potential and kinetic energy
Potential energy is stored energy; kinetic energy is the energy of motion.
Activation Energy
The minimum energy required to start a chemical reaction.
How a catalyst speeds up a reaction
By lowering the activation energy.
Decreasing pressure on a gas reaction at equilibrium
Equilibrium will shift towards the side with more gas molecules.
Example of reaction that absorbs energy
Melting ice.
Will NOT shift equilibrium
Adding a catalyst.
In an endothermic reaction, adding heat shifts equilibrium
Toward products.
Kinetic and potential energy statement
Kinetic energy increases with speed.
Has only potential energy
A stretched bowstring.
Highest point on a potential energy diagram
Activation energy.
Rate of a chemical reaction can be increased by
Lowering activation energy.
Heat content of a system at constant pressure
Enthalpy (H).
In an exothermic reaction, the products have
Lower energy than reactants.
Condition that increases collisions between reactant particles
Higher pressure (for gases).
When a system is at equilibrium
Forward and reverse rates are equal.
Endothermic process example
Boiling water.
Potential energy diagram with a high peak indicates
High activation energy.
A catalyst affects which part of a reaction profile?
Activation energy barrier.
Correct unit conversion
1 cal = 4.18 J
How a catalyst works
Decreasing activation energy.
Increases reaction rate
Adding a catalyst.
Example of kinetic energy
A moving car.
Unit of energy in the SI system
Joule.
NOT a factor that affects reaction rate
Color of reactants.
Energy change associated with a potential energy diagram
Both activation energy and heat of reaction (ΔH).
Difference between the energy of reactants and products
ΔH.
Activation energy represents
The minimum energy required to start a reaction.