Difference between revisions of "Half Equation"

Latest revision as of 16:58, 11 December 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(l) → 4Li(l) + O₂(g)	CuCl₂(aq) → Cu(s) + Cl₂(g)	2H₂O(l) → 2H₂(g) + O₂(g)
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^-

References

@@ Line 7: / Line 7: @@
 : '''Half equations''' use the letter 'e' to represent [[electron]]s.
 : '''Half equations''' can be taken from [[Balanced Symbol Equation|balanced symbol equations]].
-: The total [[charge]] on each side of a '''half equation''' must add to zero.
+: The total [[Electrical Charge|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]]: 2Li<sub>2</sub>O → 4Li + O<sub>2</sub>
+{| border="1" style="border-collapse:collapse"
+| style="height:10px; width:100px; text-align:center;" |[[Balanced Symbol Equation]]
-'''Half Equation''' at [[cathode]]: Li<sup>+</sup> + e<sup>-</sup> → Li
+| style="height:10px; width:200px; text-align:center;" |'''2Li<sub>2</sub>O(l) → 4Li(l) + O<sub>2</sub>(g)'''
+| style="height:10px; width:200px; text-align:center;" |'''CuCl<sub>2</sub>(aq) → Cu(s) + Cl<sub>2</sub>(g)'''
-'''Half Equation''' at [[anode]]: 2O<sup>-2</sup> → O<sub>2</sub> + 4e<sup>-</sup>
+| style="height:10px; width:200px; text-align:center;" |'''2H<sub>2</sub>O(l) → 2H<sub>2</sub>(g) + O<sub>2</sub>(g)'''
+|-
+| style="height:10px; width:100px; text-align:center;" |'''Half Equation''' at [[cathode]]
+| style="height:10px; width:200px; text-align:center;" |Li<sup>+</sup> + e<sup>-</sup> → Li
+| style="height:10px; width:200px; text-align:center;" |Cu<sup>+2</sup>(aq) + 2e<sup>-</sup> → Cu(s)
+| style="height:10px; width:200px; text-align:center;" |2H<sup>+</sup>(aq) + 2e<sup>-</sup> → H<sub>2</sub>(g)
+|-
+| style="height:10px; width:100px; text-align:center;" |'''Half Equation''' at [[anode]]
+| style="height:10px; width:200px; text-align:center;" |2O<sup>-2</sup> → O<sub>2</sub> + 4e<sup>-</sup>
+| style="height:10px; width:200px; text-align:center;" |2Cl<sup>-</sup>(aq) → Cl<sub>2</sub>(g) + 2e<sup>-</sup>
+| style="height:10px; width:200px; text-align:center;" |4OH<sup>-</sup> → 2H<sub>2</sub>O(l) + O<sub>2</sub>(g) + 4e<sup>-</sup>
+|}
-{| class="wikitable"
+===References===
-| style="height:20px; width:200px; text-align:center;" |[[Balanced Symbol Equation]]
+====AQA====
-| style="height:20px; width:200px; text-align:center;" |2Li<sub>2</sub>O(l) → 4Li(l) + O<sub>2</sub>(g)
-| style="height:20px; width:200px; text-align:center;" |CuCl<sub>2</sub>(aq) → Cu(s) + Cl<sub>2</sub>(g)
-| style="height:20px; width:200px; text-align:center;" |2H<sub>2</sub>O(l) → 2H<sub>2</sub>(g) + O<sub>2<sub>(g)
+:[https://www.amazon.co.uk/gp/product/1471851346/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851346&linkCode=as2&tag=nrjc-21&linkId=3ac654f4b0da781c49c855a1af4c92ea ''Half equations, pages 104, 289-91, GCSE Chemistry, Hodder, AQA '']
+:[https://www.amazon.co.uk/gp/product/178294639X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294639X&linkCode=as2&tag=nrjc-21&linkId=51599bb45a2bfaf7c1b6a978b2ca2616 ''Half equations, pages 142-144, GCSE Combined Science Trilogy; Chemistry, CGP, AQA '']
+:[https://www.amazon.co.uk/gp/product/1782945962/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945962&linkCode=as2&tag=nrjc-21&linkId=476bb5c8d1dfb5c08ac81b6d4d1c98d8 ''Half equations, pages 167-169, GCSE Chemistry, CGP, AQA '']
+:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Half equations, pages 206, 255-7, GCSE Combined Science Trilogy 1, Hodder, AQA '']
+:[https://www.amazon.co.uk/gp/product/1782945571/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945571&linkCode=as2&tag=nrjc-21&linkId=9e29fad914244909903e5e93f8a01d150 ''Half equations, pages 59, 65, GCSE Chemistry; The Revision Guide, CGP, AQA '']
+:[https://www.amazon.co.uk/gp/product/0198359381/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359381&linkCode=as2&tag=nrjc-21&linkId=47c8d1ae58d8b3a5e2094cd447154558 ''Half-equations, pages 87, 104-105, 107, 108, 123, GCSE Chemistry; Third Edition, Oxford University Press, AQA '']
-|-
+====Edexcel====
-| style="height:20px; width:200px; text-align:center;" |'''Half Equation''' at [[cathode]]
-| style="height:20px; width:200px; text-align:center;" |Li<sup>+</sup> + e<sup>-</sup> → Li
-| style="height:20px; width:200px; text-align:center;" |Cu<sup>+2</sup>(aq) + 2e<sup>-</sup> → Cu(s)
-| style="height:20px; width:200px; text-align:center;" |2H<sup>+</sup>(aq) + 2e<sup>-</sup> → H<sub>2</sub>(g)
-|-
+:[https://www.amazon.co.uk/gp/product/1782945741/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945741&linkCode=as2&tag=nrjc-21&linkId=30da4f2178da182547b62a7329d13b57 ''Half equations, pages 110-112, GCSE Combined Science; The Revision Guide, CGP, Edexcel '']
-| style="height:20px; width:200px; text-align:center;" |'''Half Equation''' at [[anode]]
+:[https://www.amazon.co.uk/gp/product/1782948147/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948147&linkCode=as2&tag=nrjc-21&linkId=f63dcd8345f4e49c717b39a228a36c7c ''Half equations, pages 134, 135, GCSE Chemistry, CGP, Edexcel '']
-| style="height:20px; width:200px; text-align:center;" |2O<sup>-2</sup> → O<sub>2</sub> + 4e<sup>-</sup>
+:[https://www.amazon.co.uk/gp/product/1292120193/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120193&linkCode=as2&tag=nrjc-21&linkId=572df39392fb4200db8391d98ae6314e ''Half equations, pages 210, 225, 231, GCSE Combined Science, Pearson Edexcel '']
-| style="height:20px; width:200px; text-align:center;" |2Cl<sup>-</sup>(aq) → Cl<sub>2</sub>(g) + 2e<sup>-</sup>
+:[https://www.amazon.co.uk/gp/product/1782945725/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945725&linkCode=as2&tag=nrjc-21&linkId=694be7494de75af3349537d34e13f7f0 ''Half equations, pages 48-50, GCSE Chemistry; The Revision Guide, CGP, Edexcel '']
-| style="height:20px; width:200px; text-align:center;" |4OH<sup>-</sup> → 2H<sub>2</sub>O(l) + O<sub>2</sub>(g) + 4e<sup>-</sup>
+:[https://www.amazon.co.uk/gp/product/1292120215/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120215&linkCode=as2&tag=nrjc-21&linkId=8f96ddb76196848bafdb124354e4cf77 ''Half equations, pages 66, 81, 87, GCSE Chemistry, Pearson, Edexcel '']
-|}
+====OCR====
+:[https://www.amazon.co.uk/gp/product/1782945679/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945679&linkCode=as2&tag=nrjc-21&linkId=a2db42f7b4bdf10cafaafa3bb9120940 ''Half equations, pages 37, 47, 48, Gateway GCSE Chemistry; The Revision Guide, CGP, OCR '']
+:[https://www.amazon.co.uk/gp/product/0198359829/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359829&linkCode=as2&tag=nrjc-21&linkId=90e8d7b4f039d53035238fa0320fe00b ''Half equations, pages 94, 111, 124, Gateway GCSE Chemistry, Oxford, OCR '']