These notes cover the whole syllabus of 9701 Cambridge International Examination, AS Level Chemistry Notes what divided into to different Units. You may find each notes have corresponded specifically in each term from syllabus.
CIE AS Chemistry Note Unit 7 - Equilibria
Alevel Chemistry Revision PC 07
Revision Material
Duration: 2nd – 8th March
Topic 7 Equilirbia
This topic illustrates that many chemical reactions are reversible and involve an equilibrium process. The consideration of the many factors that can affect an
equilibrium is an important aspect of physical chemistry.
Learning outcomes
Candidates should be able to:
7.1 Chemical equilibria: (a) explain, in terms of rates of the forward and reverse reactions, what is meant by a reversible
reversible reactions, reaction and dynamic equilibrium
dynamic equilibrium (b) state Le Chatelier’s principle and apply it to deduce qualitatively (from appropriate
information) the effects of changes in temperature, concentration or pressure on a system at
equilibrium
(c) state whether changes in temperature, concentration or pressure or the presence of a
catalyst affect the value of the equilibrium constant for a reaction
(d) deduce expressions for equilibrium constants in terms of concentrations, Kc , and partial
pressures, Kp (treatment of the relationship between Kp and Kc is not required)
(e) calculate the values of equilibrium constants in terms of concentrations or partial pressures
from appropriate data
(f) calculate the quantities present at equilibrium, given appropriate data (such calculations will
not require the solving of quadratic equations)
(g) describe and explain the conditions used in the Haber process and the Contact process, as
examples of the importance of an understanding of chemical equilibrium in the chemical
industry
7.2 Ionic equation (a) show understanding of, and use, the Brønsted-Lowry theory of acids and bases, including the
use of the conjugate acid, conjugate base (acid-I base-I, acid-II base-II) concept
(b) explain qualitatively the differences in behaviour between strong and weak acids and bases
and the pH values of their aqueous solutions in terms of the extent of dissociation
, 7.1 Chemical equilibria: reversible reactions, dynamic equilibrium
(a) Reversible reaction is a reaction in which products can be changed back to reactants by reversing the conditions
Dynamic equilibrium forward and backward reactions occurring at same rate OR the rate of forward and backward
reactions are equal / is the amount of substances in a reversible reaction are unchanged although the reaction is still
occurring. Rate of forward and backward reaction is equal. The concentrations of reactants and products remain constant
(b) state Le Chatelier’s principle and apply it to deduce qualitatively (from appropriate information) the effects of changes in
temperature, concentration or pressure on a system at equilibrium
Le Chatelier’s principle : If the conditions of a system in equilibrium are changed, the position of equilibrium moves so as
to reduce that change
Temperature - Particles move faster at a high temperature, so that the collision frequency
all the reactions will be increase.
faster as temperature rise - The average Ek of particles increases by increasing the temperature, so that
there will be more particles having higher energy than Ea.
- Increasing the number of successful collision per unit time
Concentration of - Increasing number of particles in per unit time, wo that there will be more
reactants chances of collision
Increasing the - The number of particles with higher energy than Ea in per unit volume as
concentration of reactants increasing.
speeds up the reaction. - Increasing the number of successful collision per unit time.
Catalyst - Used to speed up the reaction without chemically change.
with low the Ea for forward - Lower the Ea, so that more particles will have more energy than Ea.
and backward reaction. - The chances of collisions increase.
Surface area - increasing surface area leads to more chances of a collision
Types of catalyst
Heterogeneous in different state provides an alternative reaction pathway lower activation energy
Condition 1 400 – 500 ℃
Condition 2 200 atm
Condition 3 Fe as an catalyst
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller YNL. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.50. You're not tied to anything after your purchase.
