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k2co3 - yet another question

Discussion in 'Aquatic Plant Fertilization' started by fplata, Aug 20, 2012.

  1. fplata

    fplata Member

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    Folks,

    if i where to mix K2CO3 with 500ML RODI water and i wanted to get a concentration of 3.4 PPM per 1ml squirt into 20l of water, how many grams of dry K2c03 would i need? yes i am trying to copy ADA brightly K
     
    #1 fplata, Aug 20, 2012
    Last edited by a moderator: Aug 20, 2012
  2. fplata

    fplata Member

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    let me know if my assumption is correct; if i need 75.5 grams of K2SO4 mixed with 500 ML of water to attain a 3.4 PPM in a 20l tank when using 1ml of the solution. would i need the same amount of k2co3 to attain the same concentration? being that they are both k2?
     
  3. Biollante

    Biollante Lifetime Charter Member
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    PM'd

    Hi,

    Answer to second question pm’d as it is not consistent with original question.:eek:

    Biollante

    pm sent on 08282012:
    [h=2][​IMG] Different Molecular Weights[/h]
    Hi,

    No K2SO4 and K2CO3 have different molecular weights.[​IMG]

    Biollante



     
    #3 Biollante, Aug 20, 2012
    Last edited by a moderator: Oct 16, 2012
  4. Biollante

    Biollante Lifetime Charter Member
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    Clarifying Questions

    Hi,



    Clarifying question pm’d as it may not entirely consistent with original question.:)


    Biollante


    pm sent 08202012

    Hi,

    1. Is it important to that the amount added is 3.4-ppm K+ per 20-liters of water?
    2. Would you prefer an amount tailored to your needs?:confused:

    Biollante
     
    #4 Biollante, Aug 20, 2012
    Last edited by a moderator: Oct 16, 2012
  5. fplata

    fplata Member

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    Biollante,

    Thank you sir.

    I do like the the idea of the 3.4 PPM of k per 1ml pump on 20L of water, it works well for me. so i have done some research, but i am still s bit shot. this is what i have




    Molar mass of K2SO4 = 174.2592 g/mol of which 44.9% is K (is this assumption correct?)
    Percent composition by element

    Element Symbol Atomic Mass # of Atoms Mass Percent
    Oxygen O 15.9994 4 36.726%
    Sulfur S 32.065 1 18.401%
    Potassium K 39.0983 2 44.874%

    Molar mass of K2CO3 = 138.2055 g/mol (of which 56.6% is K)

    Percent composition by element

    Element Symbol Atomic Mass # of Atoms Mass Percent
    Carbon C 12.0107 1 8.690%
    Oxygen O 15.9994 3 34.730%
    Potassium K 39.0983 2 56.580%


    now i need to figure out the math, and this is where i need some help. Any help is highly appreciated
     
  6. Biollante

    Biollante Lifetime Charter Member
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    So As Not To Further Aggravate the Guru Team

    Hi,

    Pm'd...
    :)

    Biollante


    pm sent o08202012

    [h=2]Re: Different Molecular Weights[/h] [​IMG] Originally Posted by fplata
    Thank you, so all i need to do is find out the molecular weight of both of them and the math from there? damn we need more smart people in this world so that i can continue to be dumb and happy




    Hi,

    Yes!

    Molecular weights are the sum of the atomic weights.

    K[SUB]2[/SUB]CO[SUB]3[/SUB] has a molecular weight of 138.21, so if anyone ever asks you for mole of K[SUB]2[/SUB]CO[SUB]3[/SUB] you will know they want 138.21 grams.

    • K[SUB]2[/SUB]CO[SUB]3[/SUB] is 56.58% K[SUP]+[/SUP].

    Unless your K[SUB]2[/SUB]CO[SUB]3[/SUB], says “anhydrous” or “reagent grade” then it is likely K[SUB]2[/SUB]CO[SUB]3[/SUB]·.5H[SUB]2[/SUB]O with a molecular weight of 147.21

    • K[SUB]2[/SUB]CO[SUB]3[/SUB]·.5H[SUB]2[/SUB]O is 53.12% K[SUP]+[/SUP].

    This is a good Molecular Weight/Molar Mass Calculator.

    Thank you post is appreciated.
    :cool:

    Biollante
     
    #6 Biollante, Aug 20, 2012
    Last edited by a moderator: Oct 16, 2012
  7. fplata

    fplata Member

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    i think i figured it out

    if i want a concentration of K of 3.4 PPM when i pump 1 ML into 20 L of water I would need 76 grams of K2SO4 dissolved into 500 ML of water or 70 grams of K2c03. this is based on the molar mass. I hope i am right.

    I used the nutrient calculator found at http://calc.petalphile.com/ which gave me the below formula. based on the below and the Molar masses of each on the compounds and the percentages of K each compound have i derived at the above figures.
    To reach your target of 3.4 ppm K you will need to add 75.768 g K2SO4 to your 500.0 mL dosing container. Add 1.0 mL of that mix to your 20.0 L aquarium to yield
     
    #7 fplata, Aug 20, 2012
    Last edited by a moderator: Aug 20, 2012
  8. Snivi

    Snivi Junior Poster

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    Dont Forget solubility of k2so4 in water.
    You better do a lower density mix and add 4 ml of it.
     
  9. Biollante

    Biollante Lifetime Charter Member
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    Now The Details While Avoiding Guru Team Wrath

    Hi, PM'd:calm:

    Biollante

    pm 08202012

    [h=2][​IMG] Potassium Carbonate for the 1-pump[/h]
    Hi,

    Snivi is correct on the solubility, it is one of the reasons they use K[SUB]2[/SUB]CO[SUB]3[/SUB] to make Brighty K, if you work real hard and the K[SUB]2[/SUB]CO[SUB]3[/SUB] is pure you can get about 111-grams in for every 100-grams of water at 20°C.

    Remember for these numbers to work correctly the total solution must be 500-ml, so that 70-g K[SUB]2[/SUB]CO[SUB]3[/SUB]·.5H[SUB]2[/SUB]O is added to 400-ml distilled water then enough water is added to make 500-ml. (Without getting too technical, the K[SUP]+[/SUP] in solution is actually somewhat greater than calculated, but figure impurities and so forth make it accectable.)

    Whereas with K[SUB]2[/SUB]SO[SUB]4[/SUB] if you work real hard it is only about 13-grams in for every 100-grams of water at 20°C. Therefore, if you are going to use K[SUB]2[/SUB]SO[SUB]4[/SUB] realistically you need to mix the 76-grams into 900-mililiters of distilled water and add enough distilled water to make 1000-mililiters, then dose 2-mililiters per 20-liters to get your 3.4-ppm.

    Or use Snivi’s formula and add 38-g K[SUB]2[/SUB]SO[SUB]4[/SUB] to 950-ml distilled water and top off to make 1000-ml and dose 4-ml for every 20-l to get about 3.4-ppm.

    Biollante
     
    #9 Biollante, Aug 21, 2012
    Last edited by a moderator: Oct 16, 2012
  10. fplata

    fplata Member

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    Thank you everyone!
     
  11. Yo-han

    Yo-han Guru Class Expert

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    Correction (thanks to Biollante): Consider using KHCO3 instead of K2CO3, this raises your pH less!
     
    #11 Yo-han, Aug 21, 2012
    Last edited by a moderator: Aug 23, 2012
  12. Biollante

    Biollante Lifetime Charter Member
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    Veering Dangerously Off OP, OQ!

    Hi,

    Pm sent.:highly_amused:

    Biollante


    pm sent 08212012

    [h=2][​IMG] KHCO3[/h]
    Hi,

    KHCO[SUB]3[/SUB] is not a bad choice the solubility will allow the K[SUP]+[/SUP] concentration desired. It will add to the alkalinity, so I guess it depends what you want.

    KHCO[SUB]3[/SUB] will add more alkalinity 1.58-ppm per ppm of K[SUP]+[/SUP].

    Whereas K[SUB]2[/SUB]CO[SUB]3[/SUB] will only raise the alkalinity if there are surplus H[SUP]+[/SUP] ions around, then a maximum of 1.27-ppm per ppm of K[SUP]+[/SUP].

    Biollante
     
    #12 Biollante, Aug 21, 2012
    Last edited by a moderator: Oct 16, 2012
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