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Tahsili Chemistry (Reaction Rates and Equilibrium) Cheat Sheet by

2024 Tahsili Chemistry: Reaction Rates

Rate Of Reaction

Rate
- ΔReactants / Δt = Δproducts / Δt
Reactants are negative
Collision Theory
states that particles must collide for a reaction to occur, and must have the right orient­ation and enough energy
Activated Complex
a complex that exists very briefly in the time between the breaking down of reactants and forming of products
Activation Energy
the minimum amount of energy needed to form the activated complex
Exothermic Reaction
a reaction that releases energy; the products end up having less energy that the reactants
Endoth­ermic reaction
a reaction that must absorb enough energy to overcome the energy barrier; the products have more energy at the end
Factors that affect the rate
catalysts - the nature of the substances - Concen­tration - Surface Area - Temper­ature

Factors Affecting Equili­brium

Charac­ter­istics of equili­brium
1- fixed ratio, 2- closed system, 3-fixed temp, 4- dynamic equili­brium
Le Chatel­ier's Principle
a change in one variable that describes a system produces a shift in the position of the equili­brium, countering the change
Effects of Changing Concen­tra­tion:
higher reactant concen­tration = reaction shifts to the right, and vice versa
Effects of Changing Temper­ature
adding heat to and exothermic reaction = more reactants; adding heat to an endoth­ermic reaction = more products
Effects of Changing Pressure and Volume
Higher pressure + lower volume = lower number of moles; lower pressure + higher volume = more moles
if the number of moles are equal on both sides, pressure and volume will have no effect
 

Rate Law

Rate Law
R = k [A]x [B]y
Order of the reaction
x+y
Rate Constant (k)
is only affected by temp
Rate Constant Units
s-1 , L/mol.s , L2/mol2.s
A and B are the molar concen­tra­tions of reactants; the rate is directly propor­tional to the concen­tra­tions
the coeffi­cients are the exponents

Reversible Reactions and Equili­brium

Complete Reaction
when reactants change to products (→)
Reversible reaction
can go both ways (⇆)
Equili­brium
when the rate of the forward reaction equals the rate of the backwards one
Chemical Equili­brium Law
states that at a certain temper­ature, the ratio of the reactants and products can remain constant
for aA + bB = cC +dD
Chemical Equili­brium Law Formula
K eq = [C]c[D]d / [A]a[B]b
if K eq > 1, the products have a higher concen­tra­tion, if K eq < 1 the reactants have a higher concen­tration
Homoge­neous Equili­brium
when the reactants and products are in the same state of matter
Hetero­geneous Equili­brium
when the reactants and products are in multiple states (the pure solid and liquids are removed from the equation)

Temper­ature and The Equili­brium Constant

K eq is directly propor­tional to temp id the equation is:
endoth­ermic
K eq is inversely propor­tional to temp id the equation is:
exothermic
catalyst
increases the speed at which a reaction reaches equili­brium, but does not change the equili­brium
K sp = solubility product constant
Q sp = ionic product
if K sp > Q sp
unsatu­rated, no precip­itate
if K sp = Q sp
saturated, no precip­itate
if K sp < Q sp
saturated, precip­itate is formed

Temper­ature and The Equili­brium Constant

K eq is directly propor­tional to temp id the equation is:
endoth­ermic
K eq is inversely propor­tional to temp id the equation is:
exothermic
 

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