Question

Finish the problem:

Convert 3.8ppb of Selenium concentration into molarity

3.8ppb Se = (3.8ug Se/L) = 0.0000038g Se

1mole Se = 78.96 g

(0.0000038/78.96) = 4.8 x 10^-8 moles Se

Stuck there

Answer 1

@UnkleRhaukus

Answer 2

Don't know if what I did is right

Answer 3

Maybe it should be 4.43 x 10^-8? moles idk

Answer 4

check that calculation, im not getting 4.43

Answer 5

I got 4.8 now >_>

Answer 6

yeah

Answer 7

and you can also use 1x10^-9 mol = 1 µmol

Answer 8

But I need to find molarity, so is the volume 1 Liter?

Answer 9

yeah , im not sure why you dropped the L

= (3.8 µg Se/L) = 0.0000038 g Se / g water

Answer 10

So the molarity is 4.4 x10^-8 mol/dm^3 ?

Answer 11

/??

Answer 12

Do I divide the two values (10^-9) and (4.8x10^-8) to get micromoles?

Answer 13

What units are molarity usually measured in??

Answer 14

Liters?

Answer 15

actually you had the units right mol/L or mol/dL^3 , µmol/L or µmol/dL^3
is fine

Answer 16

What is the value in micro-molarity?

Answer 17

1 M = 1 mol/L = 1 mol/da^3

10^-9 M = 1 µM = 1 µmol/L = 1 µmol/da^3

Answer 18

so it's the same

Answer 19

you had something like 4.8 x10^-8 M which is the same as 48x10^-9 M

Answer 20

ie 48 µM

Answer 21

ok thanks

Answer 22

i think thats right , [ i haven't studied chem in about 5 years]

Answer 23

I'm doing environmental analysis and forget about some chem stuff :L