How many moles are in 2.7x1023 compounds of AlF 3

We just started a new lesson in chemistry and everyone hates it and i dont get it one bit. i hate school. h el p.balanced equationc3h8+5o2-> 3co2+4h2o1.) if you start with 14.8g of propane(c3h8) and 3.44g of oxygen, which is the limiting reactant -check my answer 2.)what mass of excess reagent is left over? 3.)what mass of carbon dioxide can be made? 4.)what mass of water is produced?

If 22.5 liters of oxygen reacted with excess of hydrogen, how many liters of water vapor could be produced?

Suppose you mix one mole of sulfuric acid (h2so4) with 1 mole of sodium hydroxide(naoh). why does the ph of the solution remain below 7? ( explain so i can get better understanding! )