1 mol of oxygen molecules = 2 * 16 = 32 grams.
x mol of oxygen = 16 grams
1/x = 32/16 Cross multiply
16 = 32x Divide by 32
16/32 = x
x = 1/2 mol
1 mol of anything has 6.02 * 10^23 somethings (molecules in this case).
1/2 mol = 6.02 *10^23 / 2
1/2 mol = 3.01 * 10^23 molecules <<<< answer
