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Self-test E.5A

Posted: Tue Oct 08, 2019 5:11 pm
by JohnWalkiewicz2J
The question goes as follows:
Calculate the amount of urea molecules, OC(NH2)2 , in 2.3 x 10^5 g of urea.
The answer it gives is 3.8 x 10^3 moles, which is correct but I thought the question was asking for the amount of individual molecules of OC(NH2)2. Which should be (3.8 x 10^3) x (6.0221 x 10^23)= 2.3 x 10^27 molecules of OC(NH2)2.

Am I missing something? or does "amount of urea molecules" actually mean moles?

Re: Self-test E.5A

Posted: Tue Oct 08, 2019 5:25 pm
by Amy Pham 1D
By the technical chemistry definition, a chemical amount generally refers to the amount expressed in moles.

From the textbook:
"The amounts of atoms, ions, or molecules in a sample are expressed in moles, and Avogadro's constant, N(sub A), is used to convert between numbers of these particles and amount in moles."

So in the case of this question, it asks for amount of urea molecules, which would mean moles of urea molecules.