Calculate the concentration of fluorine in ppm in \(500 \mathrm{~g}\) of toothpaste containing \(0.2…
Calculate the concentration of fluorine in ppm in \(500 \mathrm{~g}\) of toothpaste containing \(0.2 \mathrm{~g}\) of fluorine.
\(2 \times 10^2\)
\(4 \times 10^2\)
\(4 \times 10^0\)
\(4 \times 10^3\)
Solution
PPM or Parts Per Million is expressed as 1 milligram of substance per kilogram of parent substance.
Since, mass of toothpaste \(=500 \mathrm{~g}=0.5 \mathrm{~kg}\), and mass of fluoride ion \(=0.2 \mathrm{~g}=200 \mathrm{mg}, 0.5 \mathrm{~kg}\) toothpaste contains \(200 \mathrm{mg}\) fluoride ions, \(1 \mathrm{~kg}\) toothpaste will contain \(200 \times 2=400 \mathrm{mg}\) fluoride ions.
Hence, concentration of fluoride ion is \(400 \mathrm{ppm}\) or \(4 \times 10^2 \mathrm{ppm}\). Hence, option (b) is correct.