Definitions Flashcards
Define heat of reaction.
heat of reaction (DH) as the net change of chemical potential energy of the system.
Define exothermic reactions.
exothermic reactions as reactions which transform chemical potential energy into thermal energy .
Define endothermic reactions.
endothermic reactions as reactions which transform thermal energy into chemical potential energy.
bond breaking is ____ and that bond formation is ______.
endothermic
exothermic.
Why is bond breaking endothermic?
A reaction to break a bond always requires the input of energy and so such a process is always endothermic. When atoms come together to form new chemical bonds, the electrostatic forces bringing them together leave the bond with a large excess of energy (usually in the form of vibrations and rotations).
Why is bond formation exothermic?
When bonds are formed the system loses energy and hence increases its stability (which is the ultimate motive). Since their is a decrease in energy, the energy lost is released as heat energy and thus it is an exothermic process.
a ____ bond requires more energy to break and releases more energy when formed.
stronger
What is the heat of the reaction like for endothermic reactions?
ΔH > 0 for endothermic reactions
What is the heat of the reaction like for exothermic reactions?
ΔH < 0 for exothermic reactions
What effect do exothermic reactions have on the temperature of the reaction mixture?
exothermic reactions release heat and thus increase the temperature of the reaction mixture.
What effect do endothermic reactions have on the temperature of the reaction mixture?
endothermic reactions absorb heat and thus decrease the temperature of the reaction mixture.
Define activation energy.
the minimum energy required to start a chemical reaction OR the energy required to form the activated complex .
Define the activated complex.
a high energy, unstable, temporary transition state between the reactants and the products.
Define reaction rate.
the change in concentration per unit time of either a reactant or product.
Define a catalyst.
a substance that increases the rate of the reaction but remains unchanged at the end of the reaction
