Explore Chemistry for Biology Students with these specialized notes crafted for Year 1 students at University College London. Within this document, unravel the intricacies of ions and chemical forces, exploring concepts such as equilibrium, reaction quotients, Gibbs energy, protons, pH, solubility,...
D1: Introduction to Equilibrium, Reaction Quotients and Gibbs Energy
Ions and Forces
Aims and objectives
o Relate equilibrium constants, quotient with Gibbs free energy of reactions
o Distinguish between acid and conjugate acid and base and conjugate base
o Design a buffer and calculate the buffer pH using the Henderson-Hasselbalch equation
o Split redox reactions into oxidation and reduction reactions
o Calculate standard electrochemical potentials for electrochemical cells
o Calculate the chemical change at an electrode surface from the current passed through an
electrolyte
What makes cell processes tick?
o Biological systems
Highly organised
Systems described in individual chemical reactions
In reality – the chemical reactions are closely linked
o Cells
Organelles
Have particular roles
Can be extracted and studied chemically
Equilibrium
Fundamental concepts in chemistry
o Kinetics
How quickly or slowly a reaction occurs
o Thermodynamics
Changes in the form of energy when a reaction occurs – e.g. converting chemical energy to
heat
o Equilibrium
Reactions in which the reactants and products coexist
o Reversibility of chemical change
Reactions occurs until no change in chemical composition
E.g. ATP ADP + Pi
o A – Start with ADP and phosphate + no ATP
Concentrations of ADP and Pi will deplete
Concentrations of ATP increases
Until equilibrium concentrations are
achieved
o B – Start with ATP only + no ADP and phosphate
Concentrations of ATP will deplete
Concentrations of ADP and Pi increases
Until equilibrium concentrations are
achieved
o No matter where you start from – the reaction
occurs
Equilibrium
o aA + bB cC + dD
Reactants = A, B
Products = C, D
o Equilibrium constant K
Kc = ([C]c[D]d) /([A]a[B]b) = [products] / [reactants]
,D1: Introduction to Equilibrium, Reaction Quotients and Gibbs Energy
Kp = ((PC)c(PD)d)/ ((PA)a(PB)b) = (Pproducts) / (Preactants)
K = constant for a given reaction at a particular temperature and pressure
Units
o Kc – solutions
Concentration – moldm-3 or moldkg-1
o Kp – gases
Pressure – Pa or bar
Large K
o Equilibrium favours product formation
Small K
o Equilibrium favours reactant formation
o ∆rG
∆G = ∆H - T∆S
Energy associated with a chemical reaction that can be used to do work
o Negative ∆rG
Equilibrium favours product formation
o Positive ∆rG
Equilibrium favours reactant formation
G – total Gibbs energy of the system
Chemical potential = G / n = Gibbs energy / number of moles
o Reaction quotient Q
Measures relative amounts of products and reactants present during a reaction at a
particular point in time
Qc = ([C]c[D]d)/ ([A]a[B]b)
o
Describes the progress of the reaction
Solids and pure liquids are in their standard state and always equal to 1
, D1: Introduction to Equilibrium, Reaction Quotients and Gibbs Energy
o
More on Equilibrium and Gibbs Energy
o Equilibrium
Dynamic process in which the forward and backward reactions occur in balance
∆rG = ∆rG0 + RTlnQ
o Q = reaction quotient
o ∆rG0 = Gibbs energy at standard conditions
o R = gas constant
o T = temperature
o K is at the bottom of the curve
Right of K = positive gradient
Left of K = negative gradient
Q<K
o Reaction will favour products
o ∆rG = negative
o A+BC+D
Q>K
o Reaction will favour reactants
o ∆rG = positive
o A+BC+D
Q=K
o System is at equilibrium
o ∆rG = 0
o A+BC+D
o ∆rG = - RTlnK
pH
o Protons – H3O+
Do not exist as H+ - exist as H3O+
Controls:
Enzyme activity
Synthesis of ATP
Oxygen transport
Charge on proteins and lipids
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 sujansathiendran. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £6.49. You're not tied to anything after your purchase.
