moles = grams/molar mass
M = mols/L soln.
Please be aware that this assumes the complete solubility of the substance in water. Just looking at the molar mass, the "substance" appears it may be CaCO3 and 40.0 g CaCO3 will not dissolve in 0.50 L H2O.
what is the molarity of 40g in 0.5L of solution. Molecular weight of substance is 100.09g/mole.
5 answers
Okay, so this was a question on a quiz and I'm not sure if we were to just assume that it was dissolved? But the moles of CaCO3 is .4 correct?
Yes. 40.0g of a substance with molar mass of 100.09 = 0.4 mol of that substance.
If the question on the quiz was as you quoted it (a "substance" and it was not identified as CaCO3) then M = 0.40 mols/0.50 L and if you worked it that way you worked it correctly. When a problem is stated that way we generally assume it is completely soluble. If the substance was identified as CaCO3, it is a little more complicated than that since CaCO3 is so insoluble and it really turns into a Ksp problem. .
If the question on the quiz was as you quoted it (a "substance" and it was not identified as CaCO3) then M = 0.40 mols/0.50 L and if you worked it that way you worked it correctly. When a problem is stated that way we generally assume it is completely soluble. If the substance was identified as CaCO3, it is a little more complicated than that since CaCO3 is so insoluble and it really turns into a Ksp problem. .
Thank You! You have answered a couple of my questions and I wish I had you for my Professor as mine seems to expect knowledge and not want to teach it! (haha but not really funny!) Thanks again!
Thank you. Post anytime. It helps if you explain exactly what you don't understand about something.