ANACHEM LEC REACTION RATE/ VELOCITY AND CHEMICAL EQUILIBRIUM FINALS TERM

Rate Reaction

A quantity that tells how the concentration of a given reactant

Rapid Reaction

Is this type of rate reaction rapid or slow?
- Reaction of Na metal with H2O
- Explosion of dynamite or gunpowder

Slow reaction

Is this type of rate reaction rapid or slow?
- Change in rock structure
- Formation of coal and petroleum

Chemical Kinetics

This is the study of reaction mechanisms and reaction rates. It deals with the rate of change from initial to final states under non-equilibrium conditions

Reaction mechanism

A stepwise change involved before reactants are converted into products

Activation Energy

Minimum energy is required to produce a reaction, and minimum energy at which the reaction starts

Evidences of chemical reaction

1. Evolution of gas

2. Appearance/disappearance of color

3. Formation of solid

4. Disappearance of solid particles

5. Energy change

   These are evidences of what?

Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants

4 factors influencing the rate, speed, chemical equilibrium of a chemical reaction

Nature of reactants

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

Na+H2O - will give violet reaction because Na loses electrons easily

Temperature

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

In general, a 10 degree celsius rise in temperature will usually double or triple the rate of reaction

Nature of Reactants

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

Au+H2O - no reaction; does not even tarnish after many years of exposure

Nature of Reactants

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

Fe+H2O - Will give slow reaction; rusts slowly because Fe does not lose electrons

Nature of Reactants

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

H₂+F₂ → 2HF
at room T, the reaction is very Fast

Nature of Reactants

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

H₂+I₂ → 2HI
at room T, the reaction is very slow

Temperature

Identify if its Nature of reactants, Temperature, Presence or absence of catalyst, Concentration of reactants:

Increase in T,

Catalyst

Substance that changes/alters the speed of a chemical reaction without itself undergoing a permanent change

Hastens reaction

(+) This catalyst has what effect on the reaction

Slows down reaction

(-) This catalyst has what effect on the reaction

Enzymes

A biological catalyst that direct our body chemistry

Homogeneous, Heterogeneous Reaction

Reactions are classified into two types of reaction

Heterogenous Reaction

If more than one phase exists in the reaction mixture

Homogeneous Reaction

All reactants and products are in single phase

Chemical Equilibrium

State where the concentrations of all reactants and products remain constant with time

Irreversible Reaction

Reactions that tend to go to completion such as:
a. Formation of insoluble gas
b. Formation of unionized substance
c. Formation of an insoluble solid

Reversible Reaction

Reaction where the products of a chemical change can react to form the original substances. Wherein one reaction is the reverse of the other:
Example:
A+B

Opposing chemical reactions

The pair of reactions, the forward and the reverse, are referred to as?

Equilibrium

The point at which the rate of the forward reaction is equal to the rate of the reverse reaction. It is also a system in which two opposing reactions are proceeding at the same rate

The Law of Mass Action

This is a quantitative statement relating the velocity of a reaction to the conc. of the reactants

EQ shifts to the left

In exothermic, what happens to the EQ when T increases?

EQ shifts to the right

In exothermic, what happens to EQ when T decreases?

Product

Exothermic is considered as one of the _____?

Reactant

Endothermic is considered as one of the ________?

EQ shifts to the left

In endothermic, what happens to EQ when T decreases?

EQ shifts to the right

In endothermic, what happens to EQ when T increases?

EQ shifts to the least no. of moles

In pressure, what happens to EQ when P increases?

EQ shifts to the most no. of moles

In pressure, what happens to EQ when P decreases?

Rf = Kf [A] [B]

Rate of Forward

Rb = Kf [C] [D]

Rate of Backward

Molar conc. (moles)

[ ] what is this symbol ?

Keq

This is known as the eq. constant for the rxn

Coefficients

In the balanced chemical equation, they are the same as the exponents in the mass action expression

Change in concentration

The equilibrium existing in a chemical system maybe shifted by increasing the speed or either the forward or backward reaction

Change in temperature

The effect of T on eq. Is different however because the value of the K changes with the temperature

Chatelier’s principle

This principle is used to predict the direction of the change

Catalyst

A catalyst has no effect on the value of an equilibrium constant or on EQ concentration. It merely increases the rate of both the forward and the reverse reactions to some extend so that Eq is reached more rapidly

Pressure

Changing the volume of a system composed of gasses reactants and products changes the what?

Increase

If volume is decreased, what happens to pressure?

Increase in P

Favors Forward reaction

Decrease in P

Favors Backward reaction