ok so if given             H2So4+2NaOH---->2H2O+NaSo4  (42g H2So4)and(60g NaOH) are reacted
 
what is the limmiting reagent (reactant)?
what mass of water will be produced?
what reactant is the excess reactant and what amount of the excess reactant will remain?

thanks so much

 H2SO4+2NaOH---->2H2O+Na2SO4

Limiting reactant is the one which is used up first or gives the minimum product.Here one mole of H2SO4 is reacting with 2 moles of NaOH
Convert gm of H2SO4 --> moles of H2SO4 ---> moles of Na2SO4
similarly you can convert gm of H2SO4 --> moles of H2SO4 ---> moles of H2O
the one which gives less number of moles of H2Ois the limiting reactant.
The other one which gives more number of moles H2O is in excess.
Moles of water calculated from limiting reactant is the correct amount of water formed there.Convert moles of H2O into gram to get the mass of H2O
Now limiting reactant can be used to get the number of moles of excess reactant used during the reaction
Convert moles of limiting reactant ---> moles of excess reactant ----> mass of excess reactant used
mass of the excess reactant left = mass of the excess reactant in the starting - mass of the used