Chemistry: Redox
This flashcard set explains oxidation and reduction in terms of electron transfer, introduces redox reactions and half equations, and highlights the importance of balancing atoms and charges. It also defines oxidation state as the number of electrons involved in bonding.
What can the process of oxidation and reduction be expressed in terms of
Electron transfer
Key Terms
What can the process of oxidation and reduction be expressed in terms of
Electron transfer
Oxidation
Loss of electrons
Reduction
Gain of electrons
Where do oxidation and reduction occur
Together in a redox reaction
Half equations
Seperate equations showing oxidation and reduction processes
What must a half equation be balanced in terms of
Atoms and charge
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| Term | Definition |
|---|---|
What can the process of oxidation and reduction be expressed in terms of | Electron transfer |
Oxidation | Loss of electrons |
Reduction | Gain of electrons |
Where do oxidation and reduction occur | Together in a redox reaction |
Half equations | Seperate equations showing oxidation and reduction processes |
What must a half equation be balanced in terms of | Atoms and charge |
Oxidation state | Number of electrons involved when an atom forms a bond |
What does oxidation state refer to | One atom of the element in a compound or ion |
What does the oxidation state have | A number and a sign |
What does an uncombined element have | An oxidation state of zero |
What is the oxidation state of group one elements in compounds | +1 |
What is the oxidation state of group 2 elements in compounds | +2 |
What is the oxidation state of group 3 elements in compounds | +3 |
What is the oxidation state of hydrogen in compounds | +1 |
What is the oxidation state of fluorine in compounds | -1 |
What is the oxidation state of oxygen in compounds | -2 |
What is the oxidation state of chlorine in compounds | -1 |
What is the exception to the oxidation state rule of hydrogen in compounds | Hydride ions have an oxidation state of 1- |
What are the exceptions to the rule of oxidation state in oxygen in compounds | With fluorine/peroxide ions |
What are the exceptions to the oxidation state rule in chlorine in compounds | With oxygen |
What is the rule for oxidation state in compounds | The oxidation state of each atom in the compounds formula counts separately and the numerical sum is zero |
What is the oxidation state rule for an element existing as an ion | The oxidation state is the charge on the ion |
What is the oxidation state rule for compound ions | The sum of the oxidation states of the atoms is the charge on the ion |
What are Roman numerals in chemical names used to indicate | The oxidation state of the appropriate element E.g. Iron (II) oxide- metals oxidation state +2 |
What can we work out by assigning oxidation states | Which species have been oxidised and which reduced without writing half equations |
Oxidation (OS) | Increase in oxidation state |
Reduction (OS) | Decrease in oxidation state |
What must occur in a redox reaction in order to cause the loss of electrons from one species | Another species must accept the electrons |
What is the species that accepts electrons and causes oxidation called | An oxidising agent |
In order for a species to gain electrons in a redox reaction what must occur | Another species must donate electrons |
What is the species that donates electrons and causes reduction called | Reducing agent |
Oxidising agent | Species that accepts electrons |
Reducing agent | Is a species that donates electrons |
What must you make sure balance when writing half equations | Atoms and charges |
What is the first step in constructing complex half equations | Write down the formulae for the reactants and products and balance the atoms undergoing redox |
How to balance oxygen atoms in half equations | Add water to side with least oxygen |
How to balance hydrogen atoms in half equations | Add h+ ions to side with least hydrogen |
How to balance the charges in half equations | Add electrons to most positive side |
What must each equations show when combining half equations | One side must show reduction and the other must show oxidation |
What must the number of electrons being transferred be when combining half equations | The same- you may have to multiply one or both of the half equations |
Which species must be cancelled when combining half equations | Any species that appears on both sides |