Originally posted by ViEtGuRL
Help??? I can't find this answer ANYWHERE!!!
Why does the specific amount of 12 g of 12C (carbon-12) selected as the basis for defining 1 mole? (Why not 13g, for example? Did some law of nature require this exact mass? Or was it picked for convenience? if so, why is 12 g convenient?)
Humm,
I don't know, but I guessed something is mixed up now.
1 mol = 1 mol of a given substance, 1 mol DOES NOT equal 12g.
Lets say you got this NaCl.
Atomic weight of Na = 22.99
Atomic weight of Cl = 35.45
Total weight = 22.99+35.45=58.44
1 mol of NaCl = 58.44g
Now if you have to lets say calculate the number of moles in 500g of NaCl, you do 500/58.44 and you get 8.56.
That's how do you do.
Now, as for the Cobalt12 thing, let me explain.
To construct the periodic table of elements, Mandeliev weighted all substances and wrote their weights. He then choosed the lighest one (Hydrogen, H) and created a 'symbolical' weight.
Ex: Hydrogen is 1.01 and Calcium is 40.07. This means Calcium is 40.07 times heavier then Hydrogen. During history of Chemistry, 3 elements were used to compare. Hydrogen, Oxygen and now Cobalt12.
Why Cobalt12? Simply because it's atomical structure if the most stable of all elements.
I hope this answers your question
Btw, n7of9, stopp skipping school :biggrin2: