Electrochemistry of Solutions (Primer Lecture) PDF

Electrochemistry of Solutions (Primer Lecture) Instructor MARK RYAN R. TRIPOLE (DoPAC)  Learning Outcomes By the end of this lecture, you should be able to: Differentiate between electronic and electrolytic conductors Understand the factors that influenc...

Electrochemistry of Solutions (Primer Lecture) Instructor MARK RYAN R. TRIPOLE (DoPAC)  Learning Outcomes By the end of this lecture, you should be able to: Differentiate between electronic and electrolytic conductors Understand the factors that influence the conductance of electronic and electrolytic conductors Recall Ohm’s Law, its importance and how it starts to apply toward electrolytic solutions Chem 158 – Physical Chemistry 2 (Lecture)  Conduction of Electricity CONDUCTORS INSULATORS allow the “passage” of does not allow the electricity “passage” of electricity Chem 158 – Physical Chemistry 2 (Lecture)  CONDUCTORS allow the “passage” of electricity Electronic Electrolytic conducted by Conductors ions Conductors Conduct electricity flow of electrons Undergo without undergoing decomposition decomposition when electricity is (metals, etc.) passed through them Chem 158 – Physical Chemistry 2 (Lecture)  Electrolytic Conductors STRONG WEAK ELECTROLYTES ELECTROLYTES High degree of Low degree of ionization ionization H2SO4, HNO3, HCl CH3COOH, NH4OH NaOH, KOH etc. etc. No ionization sugar, urea, etc. NON-ELECTROLYTES Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance the degree to which a “substance” conducts electricity Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance What are the interactions that exist in solution? SOLUTE-SOLUTE SOLVENT-SOLVENT SOLUTE-SOLVENT solute solvent Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 1 INTERIONIC ATTRACTION SOLUTE-SOLUTE What does the strength of the solute-solute interaction imply about the conductance of an electrolytic solution? Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 1 INTERIONIC ATTRACTION More Less ionization ionization SOLUTE-SOLUTE Strong solute-solute Weak solute-solute interaction interaction Lower conductivity Higher conductivity Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 2 SOLVENT VISCOSITY Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 2 SOLVENT VISCOSITY SOLVENT-SOLVENT What does the strength of the solvent-solvent interaction imply about the conductance of an electrolytic solution? Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 2 SOLVENT VISCOSITY What is one of the main factors that affects the viscosity of a solvent? SOLVENT-SOLVENT INTERMOLECULAR FORCES Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 2 SOLVENT VISCOSITY Less More viscous viscous SOLVENT-SOLVENT Strong solvent-solvent Weak solvent-solvent interaction interaction Lower conductivity Higher conductivity Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 3 SOLVATION OF IONS SOLUTE-SOLVENT What does the strength of the solute-solvent interaction imply about the conductance of an electrolytic solution? Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 3 SOLVATION OF IONS ionic sphere SOLUTE-SOLVENT Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 3 SOLVATION OF IONS solvation sphere What is the consequence of having this solvation sphere? SOLUTE-SOLVENT Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 3 SOLVATION OF IONS What is the consequence of having this solvation sphere? SOLUTE-SOLVENT Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 3 SOLVATION OF IONS What is the consequence of having this solvation sphere? SOLUTE-SOLVENT Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 3 SOLVATION OF IONS Low High solvation solvation Strong solute-solvent Weak solute-solvent interaction interaction Lower conductivity Higher conductivity lower ionic mobility higher ionic mobility Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE CONDUCTORS Electronic Electrolytic Conductors Conductors How would the temperature affect the conductance of electronic conductors and electrolytic conductors? Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE Flow of electrons Electronic Conductors Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE Electronic Conductors - + + + + + - + + + + + - + + + + + Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE Electronic Conductors - + + + + + - Phonon or “elementary” + + + + + vibrations scatter electrons - + + + + + T What happens? Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE Electronic Conductors + + + + + Phonon or “elementary” + + + + + vibrations scatter electrons T + + + + + LOWER CONDUCTANCE Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE Effect on Effect on ionization? viscosity? SOLUTE-SOLUTE SOLVENT-SOLVENT Effect on solvation How would temperature sphere? affect these three SOLUTE-SOLVENT interactions? Electrolytic Conductors Chem 158 – Physical Chemistry 2 (Lecture)  Factors Affecting Electrolytic Conductance 4 TEMPERATURE Effect on Effect on ionization? viscosity? SOLUTE-SOLUTE SOLVENT-SOLVENT How would temperature Effect on affect these three solvation interactions? sphere? SOLUTE-SOLVENT T Higher conductivity Electrolytic Conductors Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 𝑉∝𝐼 Applied potential between Flow of electrical two points, driving “force” charge (flow of that pushes electrons electrons) because of through a circuit the applied voltage GEORG SIMON OHM 1789-1854 Volts (V) Amperes (A) Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 𝑉∝𝐼 𝑉 =𝐼×𝑅 Measure of a material’s opposition to electrical flow. GEORG SIMON OHM 1789-1854 ohm (Ω) Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance OHM’S LAW 𝑉 =𝐼×𝑅 𝑉 𝑅= 𝐼 GEORG SIMON OHM Interpretation? 1789-1854 Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance Applicable to materials, how about for 𝑉 solutions? 𝑅= 1 𝐼 CONDUCTANCE Siemens (S) or 1 ohm-1 (Ω-1) 𝐶= 2 𝑅 GEORG SIMON OHM 1789-1854 Interpretation? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) intrinsic to a material How does resistance relate to length (l) and cross-sectional area (A) of a conductor? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) L 2L Where is there more resistance? (assuming applied potential same for both) How does resistance relate to length (l) and cross-sectional area (A) of a conductor? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) L 2L 𝑅∝𝑙 How does resistance relate to length (l) and cross-sectional area (A) of a conductor? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) 2a a Where is there more resistance? (assuming applied potential same for both) How does resistance relate to length (l) and cross-sectional area (A) of a conductor? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) 1 2a a 𝑅∝ 𝑎 How does resistance relate to length (l) and cross-sectional area (A) of a conductor? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) 1 𝑅∝𝑙 𝑅∝ 𝑙 𝑎 𝑅∝ 𝑎 Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) Specific Resistance or Resistivity 𝑙 𝑙 𝑅∝ 𝑅=𝜌 𝑎 𝑎 Since we have specific resistance, then what is specific conductance? Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) 1 1 𝐶= or 𝑅= 𝑅 𝐶 𝑙 1 1 𝑅=𝜌 𝐾= or 𝜌= 𝑎 𝜌 𝐾 Substituting R and rho in the left side equation Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) 1 1 𝑅= 𝜌= 𝐶 𝐾 𝑙 1 1𝑙 𝑙 𝑅=𝜌 = 𝐾=𝐶 or 𝑎 𝐶 𝐾𝑎 𝑎 Substituting R and rho in the left side equation Chem 158 – Physical Chemistry 2 (Lecture)  Electrical Resistance & Conductance 3 SPECIFIC CONDUCTANCE (K) Can also be 𝑙 𝐾=𝐶 interpreted as the conductance of What are the 1cm3 of an units of K? electrolytic solution. 𝑎 𝑅=𝜌 𝑙 Interpretation? 𝑎 Chem 158 – Physical Chemistry 2 (Lecture)  What questions do you have for me? Chem 158 – Physical Chemistry 2 (Lecture)