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Thread: Alkali metals and formation of bases....

  1. #1 Alkali metals and formation of bases.... 
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    1) Hey! I wanted to know what actually are alkali metals...
    Also, why are they called so? Are they alkaline? Do they dissolve in water (for example, Sodium) and form basic solutions?

    2) Now this leads to another question....
    How are bases formed? For eg, Potassium Hydroxide.
    By mixing potassium with water or by mixing potassium oxide with water?? I mean, can a base MOH of metal M be obtained by mixing M with water?

    3) I also wanted to know that can metals and non metals be classified as acidic/basic....( Is that why alkali metals are called so because they form basic solutions?) because metals form hydroxide which are basic in nature, but then there is ammonium which also forms hydroxide..... Please clear this confusion...

    4) Final query, what is meant by alkali? I know it refers to the bases soluble in water....but what does that mean..i mean if we consider potassium oxide, it is soluble in water, and also forms a basic solution.... So it is an alkali...but potassium also dissolves in water forming basic KOH....is it too an alkali?

    In the above case of potassium oxide, it dissolves in water forming a basic solution...so it is an alkali...
    But to what do we refer when we say alkali? I mean, if we mix potassium hydroxide solution with more water, it will dissolve and the solution will still be basic....so is KOH ITSELF is an alkali too???

    Sorry for making the question too long....
    Thanks for the help!☺


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  3. #2  
    Bullshit Intolerant PhDemon's Avatar
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    1) They are called alkali metals because they form alkalis (soluble metal hydroxides when they react with water)

    2) Potassium hydroxide can be formed by reacting potassium with water:



    but it is easier to buy the solid hydroxide and make your own solutions as this reaction is quite vigorous and you can only safely add small amounts of potassium to large quantities of water making a very dilute solution. Currently most alkali metal hyroxides are made industrially by electrolysis of a solution of the alkali metal chloride although small quantities can be made by reacting the alkali metal carbonate with calcium chloride solution and filtering off the calcium carbonate precipitate.

    3) Metals and non-metals are often classified as acidic or basic based on whether they (or their oxides) form an acidic or basic solution in water. Ammonia is also an alkali (i.e. a water soluble base). This is because when ammonia is dissolved in water it produces a solution of ammonium hydroxide:



    4) What is meant by alkali is a base (a proton acceptor) that is soluble in water. So alkali is a specific term for water soluble bases that produce hydroxide ions when dissolved in water. Potassium itself is not an alkali, but the potassium hydroxide it forms when you react it with water is an alkali because it releases hydroxide ions into the solution. The key difference is that potassium does not dissolve in water, it REACTS with the water to produce a new compound.

    If you mix potassium hydroxide solution with more water you simply dilute the solution so it becomes less alkaline (the pH decreases and becomes closer to neutral.

    Hope this helps.


    Last edited by PhDemon; August 17th, 2017 at 05:49 AM. Reason: typos
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  4. #3  
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    Thank you PhDemon for the help!
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  5. #4  
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    No problem
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    Quote Originally Posted by Gaurav(-26.7) View Post
    1) Hey! I wanted to know what actually are alkali metals...
    Also, why are they called so?
    And just to add a tiny bit to PhDemon's always-excellent answers, the word "alkali" has an Arabic derivation (as do algorithm, algebra, alchemy, almanac, alcohol...). The symbol for potassium, K, comes from kalium, a German neologism coined from the Arabic word for potash.
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  7. #6  
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    Quote Originally Posted by PhDemon View Post
    1) They are called alkali metals because they form alkalis (soluble metal hydroxides when they react with water)

    2) Potassium hydroxide can be formed by reacting potassium with water:



    but it is easier to buy the solid hydroxide and make your own solutions as this reaction is quite vigorous and you can only safely add small amounts of potassium to large quantities of water making a very dilute solution. Currently most alkali metal hyroxides are made industrially by electrolysis of a solution of the alkali metal chloride although small quantities can be made by reacting the alkali metal carbonate with calcium chloride solution and filtering off the calcium carbonate precipitate.

    3) Metals and non-metals are often classified as acidic or basic based on whether they (or their oxides) form an acidic or basic solution in water. Ammonia is also an alkali (i.e. a water soluble base). This is because when ammonia is dissolved in water it produces a solution of ammonium hydroxide:



    4) What is meant by alkali is a base (a proton acceptor) that is soluble in water. So alkali is a specific term for water soluble bases that produce hydroxide ions when dissolved in water. Potassium itself is not an alkali, but the potassium hydroxide it forms when you react it with water is an alkali because it releases hydroxide ions into the solution. The key difference is that potassium does not dissolve in water, it REACTS with the water to produce a new compound.

    If you mix potassium hydroxide solution with more water you simply dilute the solution so it becomes less alkaline (the pH decreases and becomes closer to neutral.

    Hope this helps.
    The bit about reacting alkali metal carbonates with CaCl₂(aq): how does that go exactly?

    P.S. I'm about to start cleaning my kitchen with Na₂CO₃........horrible rubber gloves job......
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    Bullshit Intolerant PhDemon's Avatar
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    The bit about reacting alkali metal carbonates with CaCl₂(aq): how does that go exactly?
    I mis-typed I meant the hydroxide not the chloride!

    P.S. I'm about to start cleaning my kitchen with Na₂CO₃........horrible rubber gloves job......
    Mix it with vingar, all the chemically illiterate pseuds cleaning gurus seem to swear by fizzy sodium acetate!
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  9. #8  
    exchemist
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    Quote Originally Posted by PhDemon View Post
    The bit about reacting alkali metal carbonates with CaCl₂(aq): how does that go exactly?
    I mis-typed I meant the hydroxide not the chloride!

    P.S. I'm about to start cleaning my kitchen with Na₂CO₃........horrible rubber gloves job......
    Mix it with vingar, all the chemically illiterate pseuds cleaning gurus seem to swear by fizzy sodium acetate!
    Ah that's better. You had me scratching my head for a moment.

    Re cleaning "gurus", ah yes of course, sodium acetate. That sounds really useful for saponifying congealed grease. Not.
    In fact I'm amazed how well sodium carbonate works. Especially good inside a cooker hood, which is, by a stretch, the most repulsive part of the job.
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  10. #9  
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    Quote Originally Posted by exchemist View Post
    In fact I'm amazed how well sodium carbonate works. Especially good inside a cooker hood, which is, by a stretch, the most repulsive part of the job.
    I keep a little sodium carbonate in an open container inside the halogens cupboard, it also reacts with the bromine fumes! (I also keep sodium thiosulphate solution in there for neutralizing any spills...)
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