Electrolyte Electrolyte Solution Solution Muhammad Abbas Ahmad Zaini PhD, CEng Centre of Lipids Engineering & Applied Research, UTM Week Topic Topic Outcomes 6-7 Electrolyte Solution •The enthalpy, entropy and Gibbs energy of Ion formation in solution •Activities and activity coefficient •The Debye-Hückel theory of electrolyte solution •Chemical equilibrium in electrolyte solution It is expected that students are able to: •Define and determine activities and activity coefficient. •Evaluate mean ionic chemical potential in electrolyte and its characteristic by Debye-Hückel limiting law. Topic Outcomes
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Electrolyte Electrolyte SolutionSolution
Muhammad Abbas Ahmad ZainiPhD, CEngCentre of Lipids Engineering & Applied Research, UTM
Week Topic Topic Outcomes6-7 Electrolyte Solution
•The enthalpy, entropy and Gibbs energy of Ion formation in solution
•Activities and activity coefficient
•The Debye-Hückel theory of electrolyte solution
•Chemical equilibrium in electrolyte solution
It is expected that students are able to:
•Define and determine activities and activity coefficient.
•Evaluate mean ionic chemical potential in electrolyte and its characteristic by Debye-Hückellimiting law.
Topic Outcomes
Introduction
Solutions are homogenous mixtures of 2 or more pure substances
In solution, the solute is dispersed uniformly throughout the solvent.
Formation of Solution
Solvent molecules attracted to surface ions.
Each ion is surrounded by solvent molecules.
Enthalpy (∆H) changes with each interaction broken or formed.
Ionic solid dissolving water
Ions are solvated (surrounded by solvent)
If the solvent is water, the ions are hydrated
The intermolecular force here is ion-dipole
Terminology
Electrolyte solutions – solution that can conduct the electricity
Electrolyte – compound that if dissolved in water can to ionized
Ionization process ⇒ Produce +ve and –ve ion.⇒ Charge of the ions that conduct the electricity from
1 electrode to other electrode
Solution
Solution
Electrolyte
Weak electrolyte
Strong electrolyte
NonelectrolyteIdeal & real solutions
Neutral solutes
Strong ElectrolyteProduce ions & conduct electricity; undergo the completely ionized.
NaCl(s) → Na+(aq) + Cl–(aq)
CaBr2(s) → Ca2+(aq) + 2Br–(aq)
H2O
H2O
100% ions
If its test by using electrolyte testerwill produce light lamp and there are gas bubble
Weak Electrolyte
Conduct electricity by weak; undergo half ionized and produce a few ions
HF(g) + H2O ↔ H3O+(aq) + F– (aq)
CH3COOH ↔ H+ + CH3COO –
Non-electrolyte
Solutions that can’t conduct electricity; do not produce ions
Glucose, urea & alcohol
Dissolve as molecules in solution
E.g.
H, S, GH, S, G of ion of ion formation in formation in
solution solution
Thermodynamics of Electrolyte
The thermodynamics of electrolyte solutions is
important for a large number of chemical systems
Acid-base chemistry
Bio-chemical processes
Electrochemical reactions
Materials that dissociate into positively and negatively
charged mobile solvated ions when dissolved in an
appropriate solvent.
Solvation Shell
More energy is gained in the reorientation of the dipolar water molecules around the ions in the solvation shell
Energy flow into the system is needed to dissociate and ionize hydrogen and chlorine
Note: ∆Hof for a pure element in its standard state = 0; A solvation shell is a shell of any
chemical species that acts as a solvent and surrounds a solute species
1/2 H2(g) + 1/2 Cl2(g) H+(aq) + Cl–(aq)
Solvation shell is essential in lowering the energy of the ions thus making the reaction spontaneous
∆HR=-167.2 KJ/mol
Reaction is exothermic
Heat of Reaction
Standard state enthalpy in terms of formation enthalpies,
( ) ( )aq,ClΔHaq,HHH ffreaction−+ +Δ=Δ ooo
Note: ∆Hof for a pure element in its standard state = 0
No contribution of H2(g) & Cl2(g) (pure element) to ∆Ho
f
Cannot be measured directly by calorimetric experiment
How to obtain the information of solvated cations and anions??
Thermodynamics Functions for cations and anions
Can be obtained by making an appropriate choice for the zero of ∆Ho