want someone to check if this is right,

Q: The concentration of lead in drinking water in a home was found to be 2.1x10-9 M. What is the concentration in ppm? ppb?

MM=207.2 g/mol. 1 ppm = 1 mg/L.

A: 2.1x10^-9 mol/L x 207.2 g/ 1 mol x 1000 mg / 1 g = 4.35x10^-4 ppm.

and that is equilvalent to 4.35x10^-7 ppb.

is this correct?

3 answers

ppm = M * molar mass * 1,000

= 2.1*10^-9 * 207.2 * 10^3 = 435*10^-6
= 4.35 * 10^-4 ppm Agree with you

however would there not be more parts per billion than parts per million?
1 ppm = 10^3 ppb
so
4.35 * 10^-1 ppb
ahh yes I multiplied by 10^-3 instead lol thank you!
You are welcome :)