Difference between revisions of "Half Equation"
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| style="height:20px; width:200px; text-align:center;" |[[Balanced Symbol Equation]] | | style="height:20px; width:200px; text-align:center;" |[[Balanced Symbol Equation]] | ||
| − | | style="height:20px; width:125px; text-align:center;" |2Li<sub>2</sub>O → 4Li + O<sub>2</sub> | + | | style="height:20px; width:125px; text-align:center;" |2Li<sub>2</sub>O(l) → 4Li(l) + O<sub>2</sub>(g) |
| − | | style="height:20px; width:125px; text-align:center;" | | + | | style="height:20px; width:125px; text-align:center;" |CuCl<sub>2</sub>(aq) → Cu(s) + Cl<sub>2</sub>(g) |
| − | | style="height:20px; width:125px; text-align:center;" | | + | | style="height:20px; width:125px; text-align:center;" |2H<sub>2</sub>O(l) → 2H<sub>2</sub>(g) + O<sub>2<sub>(g) |
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| style="height:20px; width:200px; text-align:center;" |'''Half Equation''' at [[cathode]] | | style="height:20px; width:200px; text-align:center;" |'''Half Equation''' at [[cathode]] | ||
| style="height:20px; width:125px; text-align:center;" |Li<sup>+</sup> + e<sup>-</sup> → Li | | style="height:20px; width:125px; text-align:center;" |Li<sup>+</sup> + e<sup>-</sup> → Li | ||
| − | | style="height:20px; width:125px; text-align:center;" | | + | | style="height:20px; width:125px; text-align:center;" |Cu<sup>+2</sup>(aq) + 2e<sup>-</sup> → Cu(s) |
| − | | style="height:20px; width:125px; text-align:center;" | | + | | style="height:20px; width:125px; text-align:center;" |2H<sup>+</sup>(aq) + 2e<sup>-</sup> → H<sub>2</sub>(g) |
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| style="height:20px; width:200px; text-align:center;" |'''Half Equation''' at [[anode]] | | style="height:20px; width:200px; text-align:center;" |'''Half Equation''' at [[anode]] | ||
| style="height:20px; width:125px; text-align:center;" |2O<sup>-2</sup> → O<sub>2</sub> + 4e<sup>-</sup> | | style="height:20px; width:125px; text-align:center;" |2O<sup>-2</sup> → O<sub>2</sub> + 4e<sup>-</sup> | ||
| − | | style="height:20px; width:125px; text-align:center;" | | + | | style="height:20px; width:125px; text-align:center;" |2Cl<sup>-</sup>(aq) → Cl<sub>2</sub>(g) + 2e<sup>-</sup> |
| − | | style="height:20px; width:125px; text-align:center;" | | + | | style="height:20px; width:125px; text-align:center;" |4OH<sup>-</sup> → 2H<sub>2</sub>O(l) + O<sub>2</sub>(g) + 4e<sup>-</sup> |
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Revision as of 07:31, 3 January 2019
Key Stage 4
Meaning
A half equation is a type of symbol equation which shows how individual ions gain or lose electrons at an electrode during electrolysis.
About Half Equations
- In half equations only one ion is considered at a time, or the changes at one electrode.
- Half equations use the letter 'e' to represent electrons.
- Half equations can be taken from balanced symbol equations.
- The total charge on each side of a half equation must add to zero.
- The number of each element must be the same on both sides of a half equation.
Examples
Balanced Symbol Equation: 2Li2O → 4Li + O2
Half Equation at cathode: Li+ + e- → Li
Half Equation at anode: 2O-2 → O2 + 4e-
| Balanced Symbol Equation | 2Li2O(l) → 4Li(l) + O2(g) | CuCl2(aq) → Cu(s) + Cl2(g) | 2H2O(l) → 2H2(g) + O2(g)
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| Half Equation at cathode | Li+ + e- → Li | Cu+2(aq) + 2e- → Cu(s) | 2H+(aq) + 2e- → H2(g) |
| Half Equation at anode | 2O-2 → O2 + 4e- | 2Cl-(aq) → Cl2(g) + 2e- | 4OH- → 2H2O(l) + O2(g) + 4e- |