Question

500g tooth paste sample has 0.2g fluoride ion concentration. What is the concentration of fluoride in terms of ppm level ?

Answer 1

PPM or Parts Per Million is expressed as $1$ milligram of substance per kilogram of parent substance

Since, mass of toothpaste$=500g=0.5kg$, and

Mass of fluoride ion$=0.2g=200mg$

$0.5kg$ toothpaste contains $200mg$ fluoride ions,

$1kg$ toothpaste will contain $200\times 2=400mg$ fluoride ions

Hence, concentration of fluoride ion is 400 ppm