Oxygen is a diatomic gas. how many oxygen molecules are in 16 grams of oxygen?

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  

no. dot product   =0 when vecs at right angles

a.   mass number from atomic number