Question

10. A sample of toothpaste weighing 500g on analysis was found to contain 0.2g or nuorine. The conce
of fluonne in ppm is
(1) 4 * 10
(2) 4 x 10²
02
(3) 4 x 10
(4) 2 x 102
​

Answer 1

This is a way of expressing very dilute concentrations of substances. Just as per cent means out of a hundred, so parts per million or ppm means out of a million. Usually describes the concentration of something in water or soil.

One ppm is equivalent to 1 milligram of something per liter of water (mg/l)

or 1 milligram of something per kilogram soil (mg/kg).

The concentration of fluoride in terms of ppm level

PPM=no of parts of the component/total no of parts of allcomponent *10^6=.2/500 *10^6=400ppm

& Hence, the correct option is no. (2)