Question

A 500 g toothpaste sample gas 0.2 h fluoride concentration. What is the concentration of $F^-$ ions in terms of ppm level ?

• A. 250
• B. 200
• C. 400
• D. 1000

Answer 1

Answer: (C)

400

Answer 2

Amount in ppm = $\frac{Mass \, of \, solute \times 10^6}{Mass \, of \, solution}$ = $\frac{0.2 \times 10^{-6}}{500}$ = 400 ppm