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What is this element, carbon, hydrogen, oxyden or aluminum?by Rival
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#1
Jan2004, 10:38 PM

P: 14

8. [CJ6 14.P.001.] A mass of 135 g of an element is known to contain 30.1 1023 atoms. What is the element?
carbon hydrogen oxyden aluminum This is the question on my Physics practice test for my exam tomorrow. i don't know where to even begin with this one. we haven't really gone over anything like this in class... Kevin 


#3
Jan2004, 10:44 PM

P: 14

how?



#4
Jan2004, 10:49 PM

P: 658

What is this element, carbon, hydrogen, oxyden or aluminum?
1 mole contains 6.02 * 10^{23} entities here atom



#5
Jan2004, 10:54 PM

P: 14

ok so i am guessing that the equation that i need to use is n=N/NA
but how do we figure out N? 


#7
Jan2004, 11:00 PM

P: 14

ok so we have 5 moles but now what? how do we figure out what element it is?



#8
Jan2004, 11:02 PM

P: 658

Do u now approx mol wt of above given elements
Find the Mol wt with the help of Mole equation [tex]n=\frac{g}{M_0}[/tex] where M_{0} is Mol wt and g is the given wt 


#10
Jan2004, 11:13 PM

P: 14

so using the equation you gave me, i have n = 5 and g = 135, so i find Mo, which came out to be 27, and in the periodic table 27 is Co. what element is Co? but i think its wrong...



#11
Jan2004, 11:23 PM

P: 14

now that i know the mol wt, i matched it with the periodic table and it comes out to Co, but which one of the choices are Co.



#12
Jan2104, 12:07 AM

P: 658

U checked in for Atomic Number Rather than atomic wt
Atomic wt for Al is 27 (Aluminum) Co is Cobalt 


#13
Jan2104, 12:19 AM

P: 14

hehe, that could help if i looked for the right thing. Thanks alot, i really appreciate your help.
Kevin 


#14
Jan2104, 07:04 AM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,488

The whole point of a "mole" of an element is that it's weight in grams is equal to the weight of an individual atom in "atomic units". Once you know that you can identify the element.



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