
#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?




#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: 661

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: 661

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: 38,877

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.



Register to reply 
Related Discussions  
Elements of SO(3)?  Linear & Abstract Algebra  13  
Why is there greater abundance of light than heavy elements on earth?  Chemistry  3  
highest second ionization energy of elements  Biology, Chemistry & Other Homework  1  
Why those elements?  Biology  1  
Elements 115 and 113  Atomic, Solid State, Comp. Physics  9 