Difference between revisions of "Alkali"
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[[Ammonia]] also [[Chemical Reaction|reacts]] with [[water]] to produce '''Hydroxide ions''': | [[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) | : 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'] |
Revision as of 18:07, 27 October 2019
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 and the concentration.
- 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'