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Posted by on Wednesday, July 16, 2008 at 8:08pm.

Helloo.. i got a worksheet about compounds,elements andnumber of elements. it tells me to list the elements and number of atoms found in each of the compounds and i don't understand how to do get the elements and the # of atoms in the equation.. PLease help me..!!!
Common Name- Rubbing alcohol
Compound- C3H7OH
Elements-________
# of atoms of element-___________
Please and Thank You! :)

  • Science - , Wednesday, July 16, 2008 at 8:13pm

    The formul for rubbing alcohol (isopropyl alcohol) is C3H7OH.
    You have three elements; i.e., C, H, and O. I'm sure that what you are to do is to use a periodic table and find the element and symbol. C is carbon, H is hydrogen, O is oxygen.
    How many elements? Look at the subscript (we can't write subscripts but the number following the element is a subscript). In this case, there are 3 C atoms, 8 H atoms (H is written twice, once with 7 and once by itself), and 1 atom of O.

  • Science - , Wednesday, July 16, 2008 at 8:16pm

    The number of different elements is the number of different letters that appear. (Most elements are represented by a pair of letters, only the first of which is capitalized.) In this case, the different elements are C, H and O.

    To get the number of atoms, note that there are 3 C atoms, 8 H atoms and one O atom in the formula. Add up those numbers.

  • Science - , Wednesday, July 16, 2008 at 8:23pm

    Why would you have to add those numbers up?

  • Science - , Wednesday, July 16, 2008 at 8:25pm

    Because the want the number of atoms of ANY type in the C3H7OH molecule.

  • Science - , Wednesday, July 16, 2008 at 8:26pm

    how would you know how much each is worth? if you look it up in the periodic table.... is it always the same number amount of atoms for the elements?

  • Science - , Wednesday, July 16, 2008 at 8:37pm

    how would you know how much each is worth? if you look it up in the periodic table.... is it always the same number amount of atoms for the elements?

  • Science - , Wednesday, July 16, 2008 at 8:37pm

    Each atom in the formula counts as an atom, no matter how big it is. If they had asked for the mass of the molecule, then you would treat each one differntly. C weighs 12 times as much as H, for example.

    All they asked for was the NUMBER OF ATOMS in the molecule, not the weight or mass of the molecule.

  • Science - , Wednesday, July 16, 2008 at 8:39pm

    okay. I think I understand it now. Thank you.

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