This question on my Chemistry homework paper. Someone out there help me? plzz..

[Hilal]

i ll appreciate it.. !!? Calculate total grams to weigh for K2S04 fertilizer source to be applied weight percent (w/w) that pot contains 1700g of soil. the stock solutions should be prepared so that 10 ml spikes to this pot should be consumed (prepare ~%10 more total volume that the actual need) (mw for K2SO4: 89 g/mole)
in a basal treatment 20 ppm..


(sorryy i should have added this info)
basal treatemnt is 20 ppm and source is k2so4

[Jim]

Ok, then 89 Grams/Mole, I am assuming the plant needs both the Potassium and the Sulfate anion without differential uptake of the plant.

Now you are asking for a weight/weight % of solution, and actually, if you remember that 1 mL of water = 1 gram, than either unit will serve the purpose, so 1 kg of water is 1 Liter of water. Either way it works.

The term PPM has the unit "milligrams per liter" or in the w/w%, "milligrams per kilogram"

So if we need a 20 PPM solution of K2SO4, we literally need to weigh out enough so that we have 20 milligrams per liter or 20 milligrams per kilogram, got it?

If the plant is going to do a differential uptake (my wife is a horticulturalist and I have had botany myself, so I know what you are trying to do...I am an agricultural scientist myself)...

So, if the plant is going to do a differential uptake of K^+ ions, then we need to have 20 mg of K^+ and that requires a little bit more math to figure out.

Let's go there and do that:

K^+ as a percent of the total g/mole:

39.0983 g/mole K+/89 g/mole K2SO4 = 0.4393%

So, to get our 20 mg/L or 20 PPM as Potassium, then:

20/.4393 = 45.527 mg

So what I am saying is, if Potassium is the nutrient in the fertilizer and you want a 20 PPM Potassium concentration, you will weigh out 45.527 mg of K2SO4

Now, if it is the sulfate anion which is the uptake, then:

89 - 39.093 = 49.907 and just like before

49.907/89 = 0.5607

20/0.5607 = 35.67 mg

So to get 20 PPM of sulfate anion for uptake, then we would have to weigh out 35.67 mg of K2SO4 to get that and dissolve in 1 Liter of water.

so now, depending on which one it is, if it is K2SO4, K^+ or SO4^-2, you see how much we need to weigh out and add to a liter of water, which by the way, is mg/kg which is the same thing as 20 PPM

IF it is K2SO4, then weigh out 20 mg of K2SO4 and add to a 1 Liter flask, and this makes 20 PPM K2SO4 and it is the same thing as 20 mg/kg.

If it is the Potassium Ion you want, then weigh out 45.527 mg K2SO4 and dissolve in 1 liter of water to get the 20 PPM of Potassium Ion.

If is is the sulfate anion you want, then weigh out 35.67 mg K2SO4 and dissolve in 1 liter of water to get the 20 PPM of Sulfate Anion.

Now, all you have to do is adjust these numbers for the additional 10 % you need.

20 mg K2SO4 x 1.1 = 22 mg (includes 10% more)
35.67 mg K2SO4 x 1.1 = 39.24 mg for K^+, 10% more
45.527 K2SO4 x 1.1 = 50.08 mg for sulfate, 10% more

Every milliliter of these solutions will contain the 20 PPM of the relevant solution, so 10 mL of the solution will be 20 PPM.