Difference between revisions of "Alkali"
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− | + | ==Key Stage 3== | |
+ | ===Meaning=== | ||
+ | An [[alkali]] is a [[Metal Hydroxide]] [[solution]] that has a [[pH]] more than [[Neutral (Chemistry)|7]]. | ||
+ | |||
+ | : [[Noun]]: '''Alkali''' | ||
+ | : [[Adjective]]: '''Alkaline''' | ||
+ | |||
+ | ===About Alkalis=== | ||
+ | : [[Alkali]]s can be an [[Irritant]], [[Harmful]] or [[Corrosive]] and should be handled with care. | ||
+ | : [[Alkali]]s can be used to [[Neutralisation|neutralise]] [[acid]]s. | ||
+ | : [[Alkali]]s can be [[concentrated]] or [[dilute]]. | ||
+ | : [[Alkali]]s can be weak or strong which depends on the type of [[alkali]]. | ||
+ | : [[Alkali]]s turn [[Litmus]] paper blue. | ||
+ | : [[Alkali]]s turn [[Universal Indicator]] blue, indigo and purple depending on the strength of the [[alkali]]. | ||
+ | Some common [[Alkali]]s you should know: | ||
+ | *[[Sodium Hydroxide]] | ||
+ | *[[Potassium Hydroxide]] | ||
+ | |||
+ | ==Key Stage 4== | ||
+ | ===Meaning=== | ||
+ | An [[alkali]] is [[base|basic]] [[compound]] which [[dissolve]]s in [[water]] to form [[Hydroxide Ion (Chemistry)|OH<sup>-</sup> ions]] making a [[solution]] with [[pH]] greater than [[Neutral (Chemistry)|7]]. | ||
+ | |||
+ | ===About Alkalis=== | ||
+ | : [[Alkali]]s are [[base]]s in [[solution]] which form [[Hydroxide Ion (Chemistry)|Hydroxide ions]]. | ||
+ | : When a [[base]]ic [[compound]] [[dissolve]]s in [[water]] a [[Hydroxide Ion (Chemistry)|Hydroxide ion]] becomes dissociated from either the [[base|basic]] [[compound]] or from a [[water]] [[molecule]]. That [[Hydroxide Ion (Chemistry)|Hydroxide ion]] is free to move separately in the [[solution]]. | ||
+ | : The [[Hydroxide Ion (Chemistry)|Hydroxide ion]]s in an [[alkali]] will donate [[electron]]s to [[Hydrogen Ion (Chemistry)|Hydrogen ions]] to form [[water]]. This is a [[neutralisation]] [[Chemical Reaction|reaction]]. | ||
+ | : The strength of an [[alkali]] is measured on the [[pH]] scale. The more [[Hydroxide Ion (Chemistry)|Hydroxide ions]] in a [[solution]] the lower the [[pH]]. | ||
+ | |||
+ | ===Examples=== | ||
+ | [[Metal Hydroxide]]s form '''Hydroxide ions''' in [[water]]. | ||
+ | : NaOH(aq) → Na<sup>+</sup>(aq)+OH<sup>-</sup>(aq) | ||
+ | : KOH(aq) → K<sup>+</sup>(aq)+OH<sup>-</sup>(aq) | ||
+ | : Mg(OH)<sub>2</sub>(aq) → Mg<sup>+2</sup>(aq)+2OH<sup>-</sup>(aq) | ||
+ | : Ca(OH)<sub>2</sub>(aq) → Ca<sup>+2</sup>(aq)+2OH<sup>-</sup>(aq) | ||
+ | : Al(OH)<sub>3</sub>(aq) → Al<sup>+3</sup>(aq)+3OH<sup>-</sup>(aq) | ||
+ | |||
+ | [[Metal Oxide]]s [[Chemical Reaction|react]] with [[water]] to [[product|produce]] [[Metal Hydroxides]] which also form '''Hydroxide ions'''. | ||
+ | : Na<sub>2</sub>O(s) + H<sub>2</sub>O(l) → 2Na<sup>+</sup>(aq)+2OH<sup>-</sup>(aq) | ||
+ | : K<sub>2</sub>O(s) + H<sub>2</sub>O(l) → 2K<sup>+</sup>(aq)+2OH<sup>-</sup>(aq) | ||
+ | : MgO(s) + 2H<sub>2</sub>O(l) → Mg<sup>+2</sup>(aq)+2OH<sup>-</sup>(aq) | ||
+ | : CaO(s) + 2H<sub>2</sub>O(l) → Ca<sup>+2</sup>(aq)+2OH<sup>-</sup>(aq) | ||
+ | : Al<sub>2</sub>O<sub>3</sub>(s) + 3H<sub>2</sub>O(l) → 2Al<sup>+3</sup>(aq)+6OH<sup>-</sup>(aq) | ||
+ | |||
+ | [[Ammonia]] also [[Chemical Reaction|reacts]] with [[water]] to produce '''Hydroxide ions''': | ||
+ | : NH<sub>3</sub>O(aq) + H<sub>2</sub>O(l) ⇌ NH<sub>4</sub><sup>+</sup>(aq)+OH<sup>-</sup>(aq) | ||
+ | |||
+ | ===References=== | ||
+ | ====AQA==== | ||
+ | :[https://www.amazon.co.uk/gp/product/0008158762/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158762&linkCode=as2&tag=nrjc-21&linkId=a0fffa35b3ea49a63404f6704e0df7cc ''Alkali, pages 142-3, 148, 150, GCSE Chemistry; Student Book, Collins, AQA''] | ||
+ | :[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09665 ''Alkalis, page 128, GCSE Combined Science; The Revision Guide, CGP, AQA''] | ||
+ | :[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 ''Alkalis, pages 107, 112, 280, 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 ''Alkalis, pages 124-126, 130, 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 ''Alkalis, pages 146-151, 155, 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 ''Alkalis, pages 209, 247, 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=9e29fad914244909903e5e93f8a01d36 ''Alkalis, pages 51, 52, 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 ''Alkalis, pages 74-77, 92, 94, 96-97, 163, GCSE Chemistry; Third Edition, Oxford University Press, 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 ''Alkalis; reaction with acids, pages 249, 252-3, GCSE Combined Science Trilogy 1, Hodder, AQA''] | ||
+ | ====Edexcel==== | ||
+ | :[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 ''Alkalis, page 118, GCSE Chemistry, CGP, Edexcel ''] | ||
+ | :[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 ''Alkalis, page 43, GCSE Chemistry; The Revision Guide, CGP, Edexcel ''] | ||
+ | :[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 ''Alkalis, pages 105, 109, GCSE Combined Science; The Revision Guide, CGP, Edexcel ''] | ||
+ | :[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 ''Alkalis, pages 196-197, 204-205, 208-209, GCSE Combined Science, Pearson Edexcel ''] | ||
+ | :[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 ''Alkalis, pages 52-53, 60-61, 64-65, GCSE Chemistry, Pearson, Edexcel ''] | ||
+ | :[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 ''Alkalis; reactions of, pages 185, 186, GCSE Chemistry, CGP, Edexcel ''] | ||
+ | :[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 ''Alkalis; reactions of, pages 47, 65, GCSE Chemistry; The Revision Guide, CGP, Edexcel ''] | ||
+ | |||
+ | ====OCR==== | ||
+ | |||
+ | :[https://www.amazon.co.uk/gp/product/1782945695/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945695&linkCode=as2&tag=nrjc-21&linkId=ceafcc80bcad6b6754ee97a0c7ceea53 ''Alkalis, pages 112, 114, Gateway GCSE Combined Science; 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 ''Alkalis, pages 112-115, Gateway GCSE Chemistry, Oxford, 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 ''Alkalis, pages 43, 45, 64, GCSE Chemistry; The Revision Guide, CGP, OCR Gateway ''] |
Latest revision as of 22:49, 26 February 2022
Contents
Key Stage 3
Meaning
An alkali is a Metal Hydroxide solution that has a pH more than 7.
About Alkalis
- Alkalis can be an Irritant, Harmful or Corrosive and should be handled with care.
- Alkalis can be used to neutralise acids.
- Alkalis can be concentrated or dilute.
- Alkalis can be weak or strong which depends on the type of alkali.
- Alkalis turn Litmus paper blue.
- Alkalis turn Universal Indicator blue, indigo and purple depending on the strength of the alkali.
Some common Alkalis you should know:
Key Stage 4
Meaning
An alkali is basic compound which dissolves in water to form OH- ions making a solution with pH greater than 7.
About Alkalis
- Alkalis are bases in solution which form Hydroxide ions.
- When a baseic compound dissolves in water a Hydroxide ion becomes dissociated from either the basic compound or from a water molecule. That Hydroxide ion is free to move separately in the solution.
- The Hydroxide ions in an alkali will donate electrons to Hydrogen ions to form water. This is a neutralisation reaction.
- The strength of an alkali is measured on the pH scale. The more Hydroxide ions in a solution the lower the pH.
Examples
Metal Hydroxides form Hydroxide ions in water.
- NaOH(aq) → Na+(aq)+OH-(aq)
- KOH(aq) → K+(aq)+OH-(aq)
- Mg(OH)2(aq) → Mg+2(aq)+2OH-(aq)
- Ca(OH)2(aq) → Ca+2(aq)+2OH-(aq)
- Al(OH)3(aq) → Al+3(aq)+3OH-(aq)
Metal Oxides react with water to produce Metal Hydroxides which also form Hydroxide ions.
- Na2O(s) + H2O(l) → 2Na+(aq)+2OH-(aq)
- K2O(s) + H2O(l) → 2K+(aq)+2OH-(aq)
- MgO(s) + 2H2O(l) → Mg+2(aq)+2OH-(aq)
- CaO(s) + 2H2O(l) → Ca+2(aq)+2OH-(aq)
- Al2O3(s) + 3H2O(l) → 2Al+3(aq)+6OH-(aq)
Ammonia also reacts with water to produce Hydroxide ions:
- NH3O(aq) + H2O(l) ⇌ NH4+(aq)+OH-(aq)
References
AQA
- Alkali, pages 142-3, 148, 150, GCSE Chemistry; Student Book, Collins, AQA
- Alkalis, page 128, GCSE Combined Science; The Revision Guide, CGP, AQA
- Alkalis, pages 107, 112, 280, GCSE Chemistry, Hodder, AQA
- Alkalis, pages 124-126, 130, GCSE Combined Science Trilogy; Chemistry, CGP, AQA
- Alkalis, pages 146-151, 155, GCSE Chemistry, CGP, AQA
- Alkalis, pages 209, 247, GCSE Combined Science Trilogy 1, Hodder, AQA
- Alkalis, pages 51, 52, GCSE Chemistry; The Revision Guide, CGP, AQA
- Alkalis, pages 74-77, 92, 94, 96-97, 163, GCSE Chemistry; Third Edition, Oxford University Press, AQA
- Alkalis; reaction with acids, pages 249, 252-3, GCSE Combined Science Trilogy 1, Hodder, AQA
Edexcel
- Alkalis, page 118, GCSE Chemistry, CGP, Edexcel
- Alkalis, page 43, GCSE Chemistry; The Revision Guide, CGP, Edexcel
- Alkalis, pages 105, 109, GCSE Combined Science; The Revision Guide, CGP, Edexcel
- Alkalis, pages 196-197, 204-205, 208-209, GCSE Combined Science, Pearson Edexcel
- Alkalis, pages 52-53, 60-61, 64-65, GCSE Chemistry, Pearson, Edexcel
- Alkalis; reactions of, pages 185, 186, GCSE Chemistry, CGP, Edexcel
- Alkalis; reactions of, pages 47, 65, GCSE Chemistry; The Revision Guide, CGP, Edexcel