1.  Assigning numbers to the masses of chemical elements allowed chemistry to develop into a physical science and allowed for relationships between products and reactants  One mole of a substance contains 6.02x 10^23 particles  This number is Avogadro’s constant

2.  How many molecules are there in 2g of hydrogen ?  8g of oxygen ?  Atoms in 36g of carbon ?  What is the mass of 4 mol. of hydrogen atoms?  1 mol. of methane molecules ?

3.  How many atoms are there in 30.97g of phosphorus ?  What is the mass (to 2 dec. places) of 1 mol. of magnesium hydroxide ?  What is the mass of 0.0100 mol. of caffeine, C8H902N4 ?  How many moles of ammonia are there in 28.08g