Self-test E.5A

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JohnWalkiewicz2J
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am
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Self-test E.5A

Postby JohnWalkiewicz2J » Tue Oct 08, 2019 5:11 pm

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?

Amy Pham 1D
Posts: 103
Joined: Fri Aug 09, 2019 12:15 am

Re: Self-test E.5A

Postby Amy Pham 1D » Tue Oct 08, 2019 5:25 pm

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.


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