Lab Assignment #4 Questions

One of the benefits of adding gypsum (CaSO4 2H2O) is that Ca ion will replace Na ion on the exchange complex.

Hi, Maja, for question 4b, following the irrigation, because Na ions promote dispersion and colloids are far apart, so we just need to consider ESP to see which is most likely to disperse? Thanks!

yes, that is correct. Of all info provided in this question, only ESP gives you relevant info re. sodium

If Na is present in small amount in the exchange complex, is it still beneficial to replace Na with Ca? Or it is not necessary?

If a soil has a low conc. of sodium there is no need to replace it with calcium (or any other cation). The replacement would be beneficial, but it isn't necessary