How many atoms are present in 1.8 mol of Ca? Also, how many moles are in 3.4 * 10²⁶ molecules of H2O?​

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Explanation: One mole of anything, no matter what the element is, is Avogadro's number, which is 6.02 * 10^23 atoms.

One mole of Calcium is equal to it's atomic weight in grams :

1 mole Ca = 40.08 g = 6.02 * 10^23 atoms

There is a 1000mg in a gram. 1000mg * 40.08g =  

=40,080mg of Ca per mole

If you have 8.6mg of Ca that is 8.6mg / 40,080mg = .00021457 of a mole of calcium

so just multiply that by Avogadro's number to give you number of atoms:

.00021457 * 6.02 * 10^23 atoms = 1.292 * 10^20 atoms of Ca

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