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Questions on Mole Concept

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#1 Alserina



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Posted 22 September 2006 - 10:41 PM

Okay basically these are 2 questions from my Chemistry assignment, and I'd greatly appreciate any help you guys offer me!

Question 1
Electron mass = 9.1093897 x 10^-28g
Proton mass = 1.6726231 x 10^-24g
Neutron mass = 1.6749286 x 10^-24g

Using the examples of Li-7 (atomic mass 6.9) and B-11 (atomic mass 10.8) & using the above information, prove that the approx. value of Avogadro's number is 6 x 10^23. Also state with justification any assumptions you may have made.

Question 2
Think of 5 questions for which the answer is 2 moles, and arrange them in increasing order of difficulty. Also include the full solutions to these questions.

I'd appreciate it greatly if anyone could explain how I should go about doing Question 1. As for Question 2, as I'm an O/A Levels student, I'd prefer slightly less complex questions, but still reasonably challenging. Of course, you don't have to give me 5 questions at one go. One will do =)

Thanks in advance!

#2 Jay-qu


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Posted 22 September 2006 - 10:48 PM

moved to science projects and homework :D

We try to just help here instead of just answering, so I will do my best to explain :wave:

Li-7 has 3 protons 4 neutrons and 3 electrons. Hence you can calculate the mass of one atom.

Avagadros constant is the amount of atoms in 1 mol of substance. For lithium 7 it is approx 7 grams of lithium. So if you know the mass of one atom, and you know that you have N amount of atoms in 7 grams.. you can work out what N is :wave: