https://foxoyo.com/mcq/87013/a-sample-of-well-water-contains-140-gmm3-ca2-ions-and-345-gmm3-na-ions-the-hardness-of-the-sample-of-water-expressed-in-terms-of-equivalent-caco3-in-gmm3-is-assuming-atomic-masses-of-ca-40-na-23-c-12-o-16