Answer to Question #124003 in General Chemistry for Blister

Question

In a certain exchange reaction, Ca 2+ easily displaces K + from the exchange site. Give two reasons for the above observation.

Answer 1

First, as potassium is a monovalent ion (K⁺) and calcium is a divalent ion (Ca²⁺), one potassium ion will occupy one negatively-charged site while calcium will bind to anions. As the ionic interaction between calcium and negatively-charged colloids is stronger compared to potassium, the negatively charged surface will hold calcium and release potassium. Second, the mass of both cations is similar: 39 g/mol for potassium and 40 g/mol for calcium. As a result, the charge/weight ration is higher for calcium that will more easily bind the negatively-charged colloids. As a result, calcium will displace potassium from the exchange site.