Consider a water sample containing Na+ ions. The sample is placed in contact with beads that have negative charges and the Na+ ions are attracted to the beads. How can the Na+ ions then be removed?
a) Flow a polar liquid such as ethanol (CH3CH2OH)l over the beads
b) Flow a weak acid solution such as CH3COOH over the beads
c) Flow a solution of MgCl2 over the beads
d) heats the beads to evaporate Na+