Rate of reactions, equilibrium, acid and bases

Chemistry

Collision theory

particles must collide with sufficient energy and in correct orientation in order to react.

Activation energy

minimum energy particles must have for a collision to be successful.

Reaction rate

frequency of successful particle collisions.

Surface area

Decreasing particle size increases it. Increasing it means more particles are exposed and available for collisions. Resulting in more frequent successful collisions and an increased rate of reaction.

Tempreture

Is the measure of average kinetic energy particles have. When increased particles gain more kinetic energy and move faster. Means more particles are able to overcome activation energy barrier, and a greater frequency of successful collisions , increasing rate of reaction.

Catalyst

Increases the rate of reaction by providing an alternative pathway with lower activation energy. More particles will have enough energy to overcome the activation energy barrier, resulting in a greater frequency of successful collisions.

Equilibrium

When rate of forwards/backwards reaction is equal.

Kc constant

= [products]/[reactants]. Don’t include species in solid or liquid state. It has no units. Kc>1 equilm positions favours forwards reaction, more products than reactants. Kc<1 equilm favours backwards reaction, more reactants than products.

Reaction quotient, Q

is the relative amount of products to reactants. if it equals Kc, reaction is at equilibrium. If it doesn’t equal Kc, reaction isn’t at equilibrium.

Le Chateliers principle

when a change is made to the conc, temp, volume, or pressure of a system in equilibrium, the equilibrium position will shift to undo the change.

Equilibrium effect on concentration

If [reactants] increases, equilibrium will favour forwards reaction in order to use up extra reactants. If [products] increases, equilibrium will favour backwards reaction in order to use up extra products. vice verse for a decrease.

Equilibrium effect on pressure

Increase favours reaction that produces least number of gas moles. Decrease favours reaction that produces greater number of gas moles. Smaller space/volume=more pressure vice versa. Moles is the coefficient.

equilibrium effect of catalyst

it has no effect on equilibrium position. It’ll speed up both forwards/backwards reaction. Reaction reaches equilibrium faster, but equilibrium position and Kc stay the same.

Equilibrium effect on temperature

Increase will favour endothermic reaction in order to use up heat energy. Decrease will favour exothermic reaction to produce more heat energy. Only factor that changes Kc.

Bronsted Lowry Acids

donate protons (H+) in solution

Bronsted Lowry Base

accepts protons (H+) in solutions.

Strong acids/bases

will fully dissociate into ions. single arrow.

Conjugate Acid-Base pairs

Differ by a single proton (H+). An acid that donates proton to water forms a conjugative base. A base that accepts a proton from water forms a conjugative acid.

Weak acids/base

Partially dissociate into ions in solution. double headed arrows. Organic acids are weak.

Strong acids

HCL, HNO3, H2SO4, HI.

Weak acids

carboxylic acids, e.g HCOOH, CH3COOH.

Strong base

Metal hydroxides, e.g NaOH, KOH, Ca(OH)2.

Weak base

NH2, Amines, e.g CH3NH2.

Ph and [H30+]

ph is a measure of the concentration of hydronium ions in a solution. Strong acids have lower ph, due to high [H3O+], weak acids have higher ph, due to forming solutions with lower [H3O+].

Poor condcutors

Weak acids/bases.

Reactivity of acids

for acids of same concentration, strong acids contain more H3O+ ions so they’ll react faster than weak acids. (more frequent collisions, increased reaction rate).

Acidic salts

ammonium chloride. -need two equations to show how it forms acidic salt.

Good conductors

Strong acids/bases, as more ions=greater rate of reaction and better conductivity.