Summary
Summary Topic 4 - Equilibrium
- Institution
- CCEA
These are the complete notes for the CCEA A2 1 specification and have been created through multiple sources. However, they are not endorsed by CCEA.
[Show more]
Seller
Follow
Content preview
ChemistryTopic 4: Equilibrium
Dynamic equilibrium: A reversible reaction in which the rate of the forward reaction is equal to
the rate of the backward reaction and the amount of the reactants and products remains constant.
The condition for a dynamic equilibrium was that the reaction must take place in a closed system
and the result was that the macroscopic properties remain constant.
N2 + 3H2 ⇌ 2NH3
ΔH = -98 kJmol-1
When the temperature is increased, the reverse endothermic reaction is favoured (equilibrium
position shifts to the left) therefore using up the added heat. Therefore, when the temperature is
increase [N2] and [H2] increase while [NH3] decreases.
A low temperature favours the forward exothermic reaction, but since this would mean a slow
reaction, a moderate temperature of about 450 oC is used along with a catalyst at 250atm. Even
under these conditions the proportion of NH 3 present in the dynamic equilibrium is approximately
10%.
KC Expression
2
[ NH 3 ]
K C= 3
[ N2] [ H2]
Kc is the equilibrium constant
[NH3] is the concentration of NH3
[N2] is the concentration of N2
[H2] is the concentration of H2
For the Haber process the units of Kc are
Kc = (moldm-3)2/(moldm-3) (moldm-3)3
= mol-2dm6
The numerical size of the equilibrium gives an indication of the position of the equilibrium. If the
equilibrium constant is greater than the original constant, then there is a greater number of
products as the equilibrium moves right.
Equilibrium Calculations
Example 1
0.1 moles of ethanol and 0.2 moles of ethanoic acid are mixed in a total volume of 1dm 3. At
equilibrium there were 0.117 moles of ethanoic acid present. Calculate the value of K c and its units.
CH3CO2H + C2H5OH ⇌ CH3CO2C2H5 + H2O
Initial Moles 0.2 0.1 0 0
Reacting Moles 0.2 – 0.117 = -0.083 +0.083 +0.083
0.083
Equilibrium Moles 0.117 0.017 0.083 0.083
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 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 JArchy123. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
50155 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now