This video has been invaluable to my exam revision. Thank you so much.

Thank you 🙏

Very useful

so cation exchange capacity in soils appears to increases as the pH increases?

Do I understand this correctly, that with low pH, ions bond with nutrients, and this makes certain nutrients soluble and others insoluble and with high pH hydroxide bonds with nutrients and does the same thing? Please correct me if I'm wrong. Thanks for the video.

@MSJChem

9 жыл бұрын

OrthodoxofUSA Let's look at the two points separately: Effect of pH on CEC The lower the pH, the lower the CEC (which is the number of exchangeable cations a soil can hold). At low pH, the H+ ions displace other cations (such as Mg2+) from the soil; this reduces the availability of ions in the soil. At high pH, the CEC increases as OH- ions remove H+ ions from the hydroxide groups in the clay; the increases the negative charge and therefore increases the CEC. Effect of pH on nutrient availability: Acidic cations (Fe3+ and Al3+) are available at low pH; at high pH they react with OH- ions to form insoluble hydroxides. Phosphate ions (PO43-) are removed at low pH as insoluble Al3PO4. At higher pH phosphate is removed as insoluble calcium and magnesium phosphates. Nitrate ions are available at high pH Calcium and magnesium are unavailable at high pH (e.g CaCO3 reacts with H+ (at low pH) to form the Ca2+ ion which is available to the soil). Copper and zinc are available at intermediate pH. To be honest, I think that this is too much to memorize (especially all the equations for the above reactions). Just make sure that you understand the first part about the effect of pH on CEC as this comes up quite often in the exams. The rest I would just have a general understanding of the pH at which the different ions are available.

@OrthodoxofUSA

9 жыл бұрын

Mike Sugiyama Jones Thank you for your reply. Also, I take it that Al(OH)3 and Fe(OH)3 are removed from the soil. Is that correct?

@MSJChem

9 жыл бұрын

OrthodoxofUSA Yes, Al3+ and Fe3+ are removed at high pH as the insoluble hydroxides, Al(OH)3 and Fe(OH)3 (due to the reaction with OH- ions).

@OrthodoxofUSA

9 жыл бұрын

Mike Sugiyama Jones Thank you again. This helps a lot.

@MSJChem

9 жыл бұрын

OrthodoxofUSA You're welcome, best of luck in your exams.

What is the meaning of (aq) and (s)? Thanks

@MSJChem

2 жыл бұрын

(aq) is aqueous solution and (s) is solid. They are known as state symbols.

Ah. This begins to explain why porous carbon helps with soil fertility. It would create zones of acidity inside itself via anerobic bacteria, particularly lacto bacilli, but leave the more alkaline areas around it untouched. This might allow plant roots to receive reluctant nutrients like iron from the carbon.

The video is exactly 420 😉💪💨💨💨

Barley