$4.$ What is the chemical process involved in ion exchange softening of water?a$)$ Oxidationb$)$ Reductionc$)$ Precipitationd$)$ AdsorptionWhich ions are exchanged in ion exchange water softening?a$)$ Sodium and magnesiumb$)$ Sodium and calciumc$)$ Potassium and magnesiumd$)$ Potassium and calciumWhat is the byproduct of ion exchange water softening?a$)$ Calcium carbonateb$)$ Magnesium sulfatec$)$ Sodium chlorided$)$ Potassium hydroxideWhat type of resin is used to remove calcium and magnesium ions in ion exchange water softening?a$)$ Cation exchange resinb$)$ Anion exchange resinc$)$ Mixed$-$bed resind$)$ Weak acid resin