k2co3 - yet another question

[fplata]

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

[fplata]

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?

[Biollante]

Hi,

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

Biollante

pm sent on 08282012:
Different Molecular Weights

Hi,

No K2SO4 and K2CO3 have different molecular weights.

Biollante

[Biollante]

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?

Biollante

[fplata]

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

[Biollante]

Hi,

Pm'd...

Biollante

pm sent o08202012

Re: Different Molecular Weights

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.

K₂CO₃ has a molecular weight of 138.21, so if anyone ever asks you for mole of K₂CO₃ you will know they want 138.21 grams.

• K₂CO₃ is 56.58% K⁺.

Unless your K₂CO₃, says “anhydrous” or “reagent grade” then it is likely K₂CO₃·.5H₂O with a molecular weight of 147.21

• K₂CO₃·.5H₂O is 53.12% K⁺.

This is a good Molecular Weight/Molar Mass Calculator.

Thank you post is appreciated.

Biollante

[fplata]

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

[Snivi]

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

[Biollante]

Hi, PM'd

Biollante

pm 08202012

Potassium Carbonate for the 1-pump

Hi,

Snivi is correct on the solubility, it is one of the reasons they use K₂CO₃ to make Brighty K, if you work real hard and the K₂CO₃ 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 K₂CO₃·.5H₂O is added to 400-ml distilled water then enough water is added to make 500-ml. (Without getting too technical, the K⁺ in solution is actually somewhat greater than calculated, but figure impurities and so forth make it accectable.)

Whereas with K₂SO₄ 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 K₂SO₄ 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 K₂SO₄ 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

[fplata]

Thank you everyone!