Carbon monoxide (a poison) can be further oxidized up to carbon dioxide by reacting with oxygen from the air. if 40.5 grams of carbon monoxide is mixed with 16.5 grams of oxygen, how many grams of carbon monoxide are left over? note, you will have to write a balanced chemical equation first.

The problem states that carbon monoxide is reacted with oxygen to produce carbon dioxide. The balanced equation is CO + O2 -> CO2. You are also given 40.5 grams of CO and 16.5 grams of O2. Note that in the reaction, 1 mole of CO is needed to react with 1 mole of O2. So start with converting the oxygen first into carbon monoxide because you are asked to find how many grams of CO is left after the reaction.  

Number of grams CO reacted = (16.5g O2)(1 mol of O2/32 g of O2)(1 mol of CO/1mol of O2)(28 g CO/1 mol CO)
Number of grams CO reacted = 14.44 g CO  

Number of grams CO left = 40.5 g CO – 14.4 g CO = 26.1 g CO