Question

check my work for going from molarity in g/L to ppm? I have 5 mL of unknown solution that's been diluted to 50mL. Absorbance is .412 with the molar coefficient being 11750. so with concentration of (.412)/11750=3.5e-5 i have to get the ppm of the original solution. my math is: (3.5e-5)(1000)(1000)(55.85)(.05)/(5)=19.58 ppm i'm just not sure because i think thats calculated for the diluted solution but not sure if it would be different anyway

Answer 1

I am confused with your way os asking question

You want to calculate the ppm for which solution before dilluting or after dilluting to 50 mL. and your 3.5e-5 is concentration for which solution, before or after.

As per definition i know, for an aqueous solution,
ppm = 1 mg solute per liter of solution

So the whole idea for solving this will be find the concentration first
then
1.Convert mol/L to to g/1000 g of solution
2.Convert to ppm by multiplying numerator and denominator by 1000

For the first case, calculte ppm with 3.5e-5

and for dilluted case, find new concentration with M1V1=M2V2, where M!,V1 will be intitial concentration and volume and, M2,V2 is final one, put M1 = 3.5e-5 , V1 = 5 and M2 is to find, V2 = 50 , find M2 which is equal to 3.5e-6

now do the same to find ppm

1.Convert mol/L to to g/1000 g of solution
2.Convert to ppm by multiplying numerator and denominator by 1000