A 500 g toothpaste sample has 0.2 g of fluoride. The concentration of fluoride ions in terms of ppm level is ___.
The correct option is C 400 ppm
Mass of solute (i.e. concentration of F− ion) = 0.2 g in 500 g
Concentration in ppm =weight of fluoride ion(g)total weight of toothpaste (g)×106
Concentration of fluoride ion in ppm =0.2500×106=400 ppm