Question

A soil is 75% saturated with Ca+2 + Mg+2 + K+. 50 g of this soil is titrated with 20 ml of 0.1 N NaOH. Calculate the CEC.

Answer 1

CEC(CATION EXCHANGE CAPACITY), reported by nearly all soil testing laboratories, it is a calculated value that is an estimate of the soils ability to attract, retain, and exchange cation elements. It is reported in millequivalents per 100 grams of soil (meq/100g)

Ca++	40(at.wt)	2(valency)	20	(millli equivalents)
Mg++	24	2	12
K+	39	1	39	50 g of this soil is titrated with 20 ml of	0.1N NaOH Solution

Cec of the soil is = milliequivalent of NaOH used for sample titration x 100/weight of standard 0.1NaOH(if the solution is prepared for 1000 ml)

= 2x 100/4 =50 milliequivalent/100gm

but the soil sample is 50 gm

therefore the cec is 25 milliequivalent/50gm