{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}


1717f_Electrochemistry_olympiad - Raffles Raffles Junior...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Page 1 Raffles Junior College Raffles Junior College Raffles Junior College Chemistry Olympiad Chemistry Olympiad Notes Notes Notes Electrochemistry Electrochemistry Electrochemistry A REDOX PROCESSES AND ELECTROLYTES 1. Oxidation is defined as (a) loss of electron(s) (b) increase in oxidation number 2. Reduction is defined as (a) gain of electron(s) (b) decrease in oxidation number 3. A redox reaction is one in which both oxidation and reduction occurs. 4. An equation for a redox reaction may be separated into two ½ - equations: eg for the redox reaction: Cu 2+ (aq) + Zn (s) → Cu (s) + Zn 2+ (aq) Oxidation ½ - equation: Zn (s) → Zn 2+ (aq) + 2e - Reduction ½ - equation: Cu 2+ (aq) + 2e - → Cu (s) 5. An oxidising agent is one which oxidises another. In a redox reaction, the oxidising agent is itself reduced (gains e - ). 6. A reducing agent is one which reduces another. In a redox reaction, the reducing agent is itself oxidised (loses e - ). 7. Electrochemistry deals with the relationship between electricity and chemical reactions . Since electricity involves the flow of electrons, electrochemistry focuses on redox reactions. 8. Some everyday examples of redox reactions: (a) rusting (b) respiration and combustion (c) batteries and cells (d) extraction of ores (eg aluminium from bauxite) (e) electroplating
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Page 2 Some Key Terms : Electrolyte (a) An electrolyte is a compound which will conduct an electric current and be decomposed by it when in aqueous solution or in the molten state. An electrolyte conducts electricity due to the flow of charge carried by its ions . (b) A strong electrolyte is a compound which is fully ionised when molten or in solution. All ionic compounds are strong electrolytes since they are made up of ions which become mobile in the molten or aqueous state. Some covalent compounds such as HCl and HNO 3 ionise completely in water and are also strong electrolytes. Examples of strong electrolyte: NaOH, lead(II) chloride, hydrogen chloride. (c) A weak electrolyte is a compound which only partially ionises when molten or in solution. Examples: water, aqueous ammonia, most organic acids and organic bases (d) A non-electrolyte does not ionise at all and does not conduct electricity. Examples: Most organic compounds such as hydrocarbons (eg methane, ethene, benzene), alcohols, sugars, halogenoalkanes (eg chloromethane). Electrode Potentials Important information: 1. Existence of electrode potential of a metal placed in an aqueous solution of its ions: (a) Metal atoms may lose electrons and go into solution: M (s) → M n+ (aq) + ne (b) Metal ions from solution may gain electrons and form the metal: M n+ (aq) + ne → M (s) (c) An equilibrium is established between the metal and its ions: M n+ (aq) + ne M (s) (d) (For a metal that is more easily oxidised) There is a (i) build up of e on the metal surface .
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 23

1717f_Electrochemistry_olympiad - Raffles Raffles Junior...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online