| Define oxidation | gain of oxygen by an element
Loss of electrons |
| Define reduction | loss of oxygen
Gain of electrons |
| When oxidation and Reduction always take place together what is this reaction called? | Redox reaction |
| What are 2 other ways of finding out whether or not a substance has been oxidised or reduced during a chemical reaction | - Electron transfer
- Change in oxidation number |
| What are half equations? | divide reactions into separate equations, one showing oxidation and the other showing reduction |
| In a redow reaction what must be equal? | Number of electrons lost and gained |
| What is an oxidation number, and what does that show us? | Oxidation number is a number given to each atom or ion in a compound that shows us its degree of oxidation |
| What does a higher positive oxidation number mean? | That an atom or ion is more oxidised |
| What does a higher negative oxidation number mean? | That an atom or ion is more reduced |
| What are the 6 rules to deduce the oxidation number of any atom or ion by oxidaion? | 1. Oxidation number of uncombined elements is zero
2. In compounds many atoms or ions have fixed oxidation numbers
3.The oxidation number of an element in a monatomic ion is always the same as the charge
4. The sum of the oxidation numbers in a compound is zero
5. Sum of oxidation number in an ion is equal to the charge on the ion
6. Either a compound or an ion, more electronegative elements is given negative oxidation number |
| In compounds many atoms or ions have fixed oxidation numbers: (5) | 1. Group 1 elements are always +1
2. Group 2 elements are always +2
3. Fluorine is always -1
4. Hydrogen is +1 (except in metal hydrides is -1)
5. Oxygen is -2 |
| Metals always have a (+ / - ) oxidation number | Positive |
| Non-metals always have a (+ / - ) oxidation number | Negative |
| In compounds containing 2 different non-metals, the sign of the ox.no. depends on what | the electronegativity of each atom |
| What are compound ions? | Ions with 2 or more different atoms |
| What does the oxidation number refer to? | a single atom or ion in a compound |
| Oxidation is an (ic / dc) in oxidation number | Increase |
| Reduction is a (ic/dc) in oxidation number | Decrease |
| What is oxidising agent (oxidant)? | Substance which brings about oxidation by removing electrons from atom or ion. |
| What does a oxidising agent do, and when this happens. What happens to oxidation number. Give 3 examples of oxidising agents. | 1. Oxidising agent increases the oxidation number of another atom or ion
2. The oxidation number of the oxidising agent decreases
3. Oxygen, chlorine and potassium manganate(VII). |
| What is a reducing agent (reductant) ?
What happens to oxidation number ?
Give 3 examples of reducing agents. | A reducing agent decreases the oxidation number of another atom or ion
Oxidation number of the reducing agent increases
3. Hydrogen, potassium iodide and reactive metals (aluminium). |
| Names of ions containing oxygen and one other element end in | '-ate' |
| Names of inorganic acids containing oxygen end in | '-ic' |
| What are the steps in constructing equations using oxidation numbers (4)? | 1. Identify oxidation number changes
2. Balance oxidation number changes
3. Balance charges
4. Balance atoms |
