Aim: What is KINETICS?
Kinetics- study of the rate (speed) and mechanism (how it happens) of a chemical rxn.
-If 1 step in the rxn is slow then the entire rxn will be slow.
Aim: What factors affect the RATE of a rxn??
-Effective collisions- in order for the rxn to work, the particles in the rxn must hit each other in the right angle
Factors that affect the rate of a rxn
1) TEMPERATURE- if you increase the temp. , then the molecules move faster (because of increase in avg. kinetic energy) therefore increasing the chance for effective collisions.
2) PRESSURE- If u increase the pressure that means your lowering the volume. If u decrease the volume then the chance for an effective collision goes up. THIS ONLY AFFECTS GASES, NOT SOLIDS OR LIQUIDS.
3) CONCENTRATION- increase in concentration means that there are more particles to collide, increasing the chance of effective collisions
IF U DECREASE THESE AMOUNTS THEN U DECREASE THE CHANCE OF EFFECTIVE COLLISIONS MAKING IT GO SLOWER.
Aim: Potential energy diagrams
A + B + ENERGY (doesn’t matter how much KJ) → C+ D
This FOWARD rxn is endothermic. If the Heat (KJ) is before the arrow then the rxn is endothermic. Endothermic means that A + B need to absorb energy in order to make C + D. The following diagram is how the energy chart would look for an endothermic rxn. The backwards rxn of this is C +D → A + B+ ENERGY. This rxn is exothermic
A + B → C + D + ENERGY
This forward rxn is EXOTHERMIC. If the heat is after the arrow that means heat was released. So therefore it is exothermic
1) Potential Energy of reactants ( A + B)
2) PE of product
3) Change from reactant to product ( delta H, ▲H)
4) Activation energy of products
5) Activated complex if there’s a catalyst- just makes it faster
6) Activated complex
7) AE of reactants
Aim how do we predict which rxn will occur
SPONTANIOUSLY?
Spontaneous- happen on
its own with no outside help. Not how fast it goes.
Factors that effect spontaneous runs.-
1) ENTHALPY- Delta H
a) Increase enthalpy (endothermic) = less spontaneous bec. Outside heat is needed, thus making it not spon.
b) Decreasing enthalpy (exothermic) = more spontaneous. No outside heat is needed.
2) Temperature – some rxn will spontaneously at some temps but not others.
3) ENTROPY- disorder. From solid to liquid to gas increases spon rxns. From gas TO liquid to solid decreases its chance of spon rxns.
Decrease in enthalpy + increase in entropy = prob spontaneous.
Increase in enthalpy + decrease in entropy = prob not spon.
Aim: What is
EQUILIBRIUM?
Equilibrium- when two opposite rxns occur at the same speed.
A + B ↔ C + D
Question: what is equilibrium?
1) When the atoms of two rxns react at the same speed
2) when the atoms of two rxns have the same amount of concentration
Answer is a she will
DEFINITELY ASK THIS QUESTION OR SUMTIN LIKE IT.
Types of equilibriums.
1)
Solution equis-
When a solution is saturated. ALL
Saturated solutions are at equi.
2)
Phase equis.-
the equilibrium between two phases.
Of H2O, AT 0 CELCIUS- FREEZING-MELTING (FUSION) EQUI
100 CELCIUS- EVAPORIZATION- CONDENSATION EQUI
3) CHEMICAL equi- 2 opp chem. Rxns occur at same time
N2 + 3H2 ↔ 2NH3
Aim: Le Charteliers Principal
When a stress (change in anything) disturbs a system, the system tries to relieve that stress to reestablish equilibrium
N2 + 3H2 ↔
2NH3 + heat
Stress- ↑ temp (heat)
The direction of shift (more will be produced) will go to N + H because if heat is added then it will make the 2NH3 + heat rxn go faster producing N + H. If the temp goes up the shift will always go the endothermic rxn way (2NH3 + heat ↔ N2 + 3H2)
↑N ↑H ↓NH3
Stress- ↓ Temp
The direction of shift will go towards 2NH3. If heat is taken away, then less N + H will be produced. Since less of that is being produced that means that more NH3 will be produced. The shift of decrease in energy will always go the exothermic way.
Opposite effects as above
Stress- ↑ N
The amount of NH3 will go up because there is more N in the rxn. If there are more N’s in the rxn then more effective collisions will occur making NH3
↓H bec more collisions will happen making NH3 ↑NH3
Stress- ↓N
There are less N’s so the N+H → NH3 will go slower then the NH3 → N+H
So there will be
↑H bec there will be more H made then used ↓NH3
A catalyst has no effect on the change of equilibrium. She will ask what does a catalyst have no effect on and 1 of the choices will prob be no effect on the speed of either rxn. That is wrong. It has no effect on the shift of the equilibrium.
Aim: Acids and Bases
Neutral- a solution that contains the same amount of acids and
bases. NEUTRAL DOES NOT MEAN WATER.
WATER IS A TYPE OF NEUTRAL SOLUTION.
Arrhenius Acid- Any compound that when its put into water, gives off H2 IONS (will def ask if gives off ions or atom. Answer ions)
HCL+H2O → H3O + CL
It becomes H 3!!!!! O
IN QUESTION IT MIGHT ASK WHICH: ACID, GIVES OFF HYDROGEN, (NOT HYDROXIDE) OR SOMETHING WITH H3O …………………….
REMEMBER: C2H3C00H IS
AN ACID NOT A BASE
IT WILL NEVER CONTAIN A METAL
H IS USUALLY 1ST LETTER
BECOMES H3O
H MUST BE THE + ATOM IN THE COMPOUND
Ar…….. Base- Any compound that gives off OH in H2O
REMEMBER: USUALLY METALS + OH
ANY SOLUTION THAT HAS C’S AND H’S THEN OH IS AN ALCHOHOL, NOT A BASE
ALL ACIDS AND BASES HAVE AMOUNTS OF THE OPPOSITE OF THEM IN THE SOLUTION, JUST VERY SMALL AMOUNTS
