Question

The total cation content of natural water is often de- *24-11. ined by exchanging the cations for hydrogen ions on a strong-acid ion-exchange resin. A 25.0-mL term sample of a natural water was diluted to 100 mL with distilled water, and 2.0 g of a cation-exchange resin were added. After stirring, the mixture was filtered and the solid remaining on the filter paper was washed with three 15.0-mL portions of water. The filtrate and washings required 15.3 mL of 0.0202 M NaOH to give a bromocresol green end point. (a) Calculate the number of milliequivalents of cation present in exactly 1 L of sample. (Here, the equivalent weight of a cation is its formula weight divided by its charge.) Report the results in terms of milligrams of CaCO3 per liter. (b)