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Determining ppm of KCl

Discussion in 'Water Chemistry' started by Solcielo lawrencia, Aug 5, 2015.

  1. Solcielo lawrencia

    Solcielo lawrencia Aspiring Aquascaper

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    According to YANC:
    1 tsp of KCl into 60 gallons = 10.4ppm of K, 3.7ppm of Cl.

    Shouldn't it be equal parts for each element since KCl is 1 part K, 1 part Cl? How does K become 3x more Cl?
     
  2. isla

    isla Aspiring Aquascaper

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    one spoon : volume or weight ....
    i think it's should depend of atomic weight of the element and cannot be 1 part / 1 part
     
  3. Solcielo lawrencia

    Solcielo lawrencia Aspiring Aquascaper

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    Yeah, I don't remember my chemistry course but I figured that:

    K = 39.10
    Cl = 35.45
    KCl = 74.55

    So by weight, K isn't that much heavier than Cl, so why does YANC indicate the K is almost 3x the amount of Cl?
     
  4. Solcielo lawrencia

    Solcielo lawrencia Aspiring Aquascaper

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    Here's how to convert weight of KCl to ppm of each element in solution. 1 tsp of KCl fertilizer weighs 5.6 grams.

    1) calculate the moles by dividing weight (grams) from the molecular weight (5.6 grams / 74.55 = 0.074M/L)
    2) multiply the M/L with the molecular weight of the target molecule (K=39.09 x 0.075M/L = 2.93)
    3) convert to mg/L (ppm) by multiplying the result by 1000 (2.93 x 1000 = 2930mg/L)
    4) divide the result by the volume of the tank (2930ppm/227L = 12.9ppm)

    To calculate the chloride concentration, perform steps 2-4 again with Cl in place.
    Cl=35.45 x 0.075M/L = 2.66g/L x 1000mg/L = 2660mg/L / 227L = 11.7mg/L

    Thus, 5.6 grams (1 tsp) of KCl into 60 gallons (227L) of water results in K= 12.9ppm and Cl= 11.7ppm

    Therefore, YANC is in error.
     

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