3.1.10 - Equilibrium constant K p for homogeneous systems
Summary
Summary notes for AQA A-Level Chemistry Unit 3.1.10 - Equilibrium constant K p for homogeneous systems (A-level only)
7 views 0 purchase
Course
3.1.10 - Equilibrium constant K p for homogeneous systems
Institution
AQA
Book
AQA A Level Chemistry Student Book 2
Summary notes for AQA A-Level Chemistry Unit 3.1.10 - Equilibrium constant K p for homogeneous systems (A-level only) by an Imperial College London MSci Chemistry graduate. Notes divided into the following sections: Mole Fractions, Partial Pressure, Equilibrium constant K p
Summary notes for AQA A-Level Chemistry Unit 3.3.16 - Chromatography (A-level only)
Summary notes for AQA A-Level Chemistry Unit 3.3.15 - Nuclear magnetic resonance spectroscopy (A-level only)
Summary notes for AQA A-Level Chemistry Unit 3.3.14 - Organic synthesis (A-level only)
All for this textbook (13)
Written for
A/AS Level
AQA
A Level Chemistry
3.1.10 - Equilibrium constant K p for homogeneous systems
All documents for this subject (10)
Seller
Follow
bookishresearcher
Content preview
Section 1 : Physical Chemistry
Equilibrium Constant Kp for Homogeneous Systems
Mole Fractions
The mole fraction of a component, A, in a gaseous mixture is denoted xA + is calculated by dividing the
amount, in moles, of A by the total amount of moles of gas in the mixture.
• For: A(g) + B(g) ⇌ C(g) …
- xA = nA / (nA + nB + nC)
• where nA, nB + nC are the amounts, in moles, of A, B + C present in the mixture.
• The sum of the mole fractions of all of the components in a mixture will be equal to 1.
Partial Pressure
The partial pressure of a component, A, in a mixture of gases is the contribution which that gas makes
to the total pressure of the gas mixture.
• The partial pressure of A is denoted p(A) + its units are Pa (or kPa = 103 Pa, or MPa = 106 Pa).
The partial pressure of A, p(A), in a mixture is given by the following expression:
p(A) = xA x P
• ∴ partial pressure = mole fraction x total pressure
Equilibrium Constant (Kp)
The equilibrium constant Kp is deduced from the equation for a reversible reaction occurring in the gas
phase. Kp is calculated from partial pressures for a system at constant temp.
For the general case of a gaseous homogeneous equilibrium:
aA(g) + bB(g) ⇌ cC(g) + dD(g)
p(C)c p(D)d where p(C) represents the partial pressure of C in the equilibrium mixture and c
Kp =
p(A)a p(B)b is the balancing no. for C. Same applies to A, B + D.
The units are in terms of partial pressures in Pa but the overall power depends on the balancing
numbers in the eq. for the reaction.
(Pa)(c+d)
∴ units of Kc =
(Pa)(a+b)
∴ if Kp has no units then it is because there are an equal no. of moles on both sides of the eq. + they
cancel each other out in the Kp expression.
E.g. for the following reaction:
H2(g) + Br2(g) ⇌ 2HBr(g)
1.00 mol of H2(g) was mixed w/ 1.00 mol of Br2(g) + the mixture allowed to attain equilibrium.
0.824 mol of HBr(g) were present in the equilibrium mixture. Calculate a value for Kp.
Kp = p(HBr)2/[p(H2)p(Br2)] = (0.412P)2/(0.294P)2 = 1.96
∴ units = (Pa)2/(Pa)2 = no units, because the partial pressures cancel out in the expression
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 bookishresearcher. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.04. You're not tied to anything after your purchase.
