Electrolytes and electrolysis Vladan Bernard Electrolytes •„An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons.“ • Electrolyte solutions can also result from the dissolution of some biological (e.g., DNA, polypeptides) and synthetic polymers (e.g., polystyrene sulfonate), termed "polyelectrolytes", Definitions: Ionization, electrolytes •Definition: Ionization • - Substance acquires negative/positive charge by gaining/losing electrons • - In water: substance breaks up into ions •Example NaCl to Na+ and Cl- • •• Definition: Electrolytes • - Substance that undergoes ionization • - In water: solution of electrolyte conducts energy – Examples: Salts, acids, bases Definitions: Equilibrium, dissociation •Equilibrium • – Between ionic compound (NaCl) and free ions (Na+ + Cl-) •Dissociation • – Separation of ions (separation of Na+ and Cl-) NaCl Na+ Cl- Ionic compound, crystal lattic NOT conduct electricity Free ions in water solution Conduct electricity Electrolytes – weak and strong •Weak electrolytes –Dissociates only partially (in equilibrium) –NH4OH NH4+ OH- •Strong electrolytes –Dissociates (breaks up) completely into ions (no equilibrium) –NaOH Na+ OH- http://wps.prenhall.com/wps/media/objects/4677/4789905/images/table4_1.gif • Ions Ions •free charge carriers •Ions are two signs - positive +Q and negative -Q. To receive the atom (+) charge, it is enough to lose at least one electron in its orbit, then the balance will be disrupted and protons becomes larger than that of electrons. There is a deficit, the lack of electrons, atoms begin to crave to get a new electron. Such an atom turns into a positive ion, or else call it more cation. To obtain a negative ion (-), which is also called an anion sufficiently electrically neutral atom attached at least one extra electron. • Electric current •If there is a electrolyte where only anions, they will move toward the anode, if the conductor is only cations, they will move toward the cathode. • •If the electrolyte has both types of ions, then each of them will move to their side. • Výsledek obrázku pro electrolysis Electric current of free charges •Connected with Faraday´s law of electrolysis • •Definition „ the mass m of substance liberated from an electrolyte solution is proportional to the product of the current I and the time t of current passage through the electrolyte“ • • m = AIt = AQ •A-electrochemical equivalent. • Electric current – temperature effect •Another difference from the conduction current is the temperature dependence. For metals, the increase in temperature degrades their conductivity, resistance of metals by heating increases. • •In the case of conductive liquids inverse dependence. The increase in temperature improves motility ions upon heating of the conductive fluid resistance decreases. • Conductometry Conductometry Conductometers •Analyzing quality of water •Measuring presence of ionts in solutions •Polarographic methods Jaroslav Heyrovský (1890-1967) Czech chemist and inventor. Heyrovský was the inventor of the polarographic method, father of the electroanalytical method, and recipient of the Nobel Prize in 1959 for his discovery and development of the polarographic methods of analysis. Electrolysis •In chemistry and manufacturing, electrolysis is a technique that uses a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. • •Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. • • Rust removal from small iron or steel objects by electrolysis can be done. • •Electroplating, where a thin film of metal is deposited over a substrate material. Electroplating is used in many industries for either functional or decorative purposes, as in vehicle bodies and nickel coins. Electroplating https://www.youtube.com/watch?v=OxhCU_jBiOA