Question

The federal limit for cadmium in drinking water is 0.010 mg per liter of solution. What is the molar
concentration of a Cd solution that has reached the limit? (molar mass Cd = 112.41)

Answer 1

M = moles / L convert 112 to moles and then?

Answer 2

Start with the limit 0.010 mg in 1L--> Convert 0.01mg to moles.

Answer 3

Sorry, but I'm kinda confused on how to convert .010 mg to moles :S

Answer 4

What is the relationship between g and moles?

Answer 5

Number of moles = (# of grams) ÷ (molar mass)
Number of grams = (# of moles) × (molar mass)
?

Answer 6

Yes, So you have # mg = 0.010. Convert that to g. Then divide by molar mass (given in problem) You will get moles.

Answer 7

Okay, so I get 8.8 x 10^-8 moles

Answer 8

Molarity is moles per litre. Can you convert your moles to Molarity now? Look at the information given to you in the problem.

Answer 9

Okay, So M = 8.8 x 10^-8 moles / ? 0.010 mg per liter?

Answer 10

or do i just divide by 1 L?

Answer 11

You have converted 0.010 mg to moles. The problem says"The federal limit for cadmium in drinking water is 0.010 mg per liter of solution. " So if you had 0.010 mg or 8.8 x 10^-8 moles in 1 L, you would reach the limit. So in terms of molarity, it is 8.8 x 10^-8 in 1L or 8.8x 10-8 M. Makes sense?

Answer 12

Ah okay. Yes, It makes sense now. Thank you so much!!

Answer 13

You have to read the problem. Then write down what is given. Only then think through it to the next step. Which is what relationships do you know, formulae etc. Here you needed relatioship for moles and molarity.