Kinetics Unit Flashcards
What is kinetics?
The study of chemistry that examines the rates of chemical reactions and the mechanisms by which chemical reactions take place.
What is collision theory?
The concept of kinetics that says in order for a reaction to take place reactant particles must collide.
What is an effective collision?
a collision which results in a reaction
what conditions must be present for an effective collision?
- particles must have enough kinetic energy
- the particles must collide at the proper angle.
in exothermic reactions, does potential energy decrease or increase?
decrease
in endothermic reactions, does potential energy decrease or increase?
increases
what is activation energy
the amount of energy required to initiate a chemical reaction. it is added to the reactants and forms the activated complex
what is heat of reaction
the amoutn of energy released in an exothermic reaction or absorbed in an endo thermic reaction
what is delta H the difference of
the final potential energy - the initial potential energy
if the reaction is exothermic, is the heat of reaction positive or negative
negative
if the reaction is endothermic, is the heat of reaction positive or negative
positive
what are reversible reactions
reactions where once the products form, they can react with each other, reforming the reactants.
what are catalysts
increases the rate of a chemical reaction by lowering the activation energy required. catalysts do not change delta H for the forward or reverse reaction
how does concentration affect rate of reaction
if the concentration is increased, the reaction rate will be increased. b/c the greater the concentration, the form effective collisions and the fewer water molecules that interfere with collisions.
how does temperature affect rate of reaction
the higher the temperature, the greater the rate of reaction because the molecules of a substance will move faster causing more effective collisions.
how does the nature of the reactants affect rate of reaction
ionic compound reactions are faster because the bonds are already broken and only new ones have to be formed. in covalent substances, the bonds have to be broken first.
how does presence of a catalyst affect rate of reaction
it increases it by providing an easier pathway for the reaction. the catalyst remains unchanged after the reaction.
how does surface area affect the rate of reaction
the smaller the particles, the greater the rate of reaction. more area is exposed for the substance to react with and there are more chances for the reactant particles to collide.
how does pressure affect the rate of reaction
has little affect on non-gases. for gases, increased pressure will result increase rate of reaction by increasing the frequency of collisions.
what is enthalpy
the total heat content of a system (at constant pressure) delta h is also called change in enthalpy
at is standard heat of formation
delta Hf ^o
change in enthalpy when one mole of a compound is formed from its elements at one atmosphere and 298k
where is the energy term put for exothermic reactions
with the products, endothermic is the opposite
what is Hess’ law of heat Summation
if a chemical reaction can be expressed as the algebraic sum of two other equations, the heat of reaction for the final reaction will be the sum of the heats of reaction of the other 2 equations
what are spontaneous reactions?
a reaction in which, once begun, with continue with no outside intervention, it favors the formation of products at the specified conditions of the reaction.
what is enthalpy
the loss or gain of heat
what do systems tend to go to
lower states of energy, or enthalpy
are exothermic reactions or endothermic reactions more likely to be spontaneous
exothermic reactions are more likely to be spontaneous because there is more energy in the reactants than the products
what is entropy
the measure of disorder or randomness of a system
what is the tendency of nature in regards to entropy
nature tends to go to a state of lower energy and higher entropy
do compounds or free elements have more entropy
free elements have greater entropy or disorder
if a state moves in an endothermic reaction (solid to liquid) what happens to dela S
it is positive, entropy increases
what does an increase in entropy favor
a spontaneous reaction
what is gibs free energy equation
delta G = delta H - T delta S
what is the gibs free energy equation used to determine
if a reaction is spontaneous
what does delta g have to be in order for the reaction to be spontaneous
negative
if delta H is negative and delta S is positive, what will delta G be
negative and will favor a spontaneous reaction
if delta H is positive and delta S is negative, what will delta G be
positive, not spontaneous
