P4+10Cl2=4PCl5 balanced equation

Question

How do I find what the mass of the excess reactant that will remain when the reaction is complete?

Answer 1

Typically you would need the mass of a particular reactant. Once you have this you can calculate the amount of moles where moles = grams/ gram formula mass. Then you have to look at the coefficients, and try to determine which reactant is the limiting reagent (most likely Chlorine). You would then subtract the number of moles of the limiting reactant from the remaining reactant's amount of moles and then multiply this remainder by the gram formula mass of the remaining reactant to get the left over amount in grams of the reactant that wasn't used up. Feel free to reach out to me for more in depth explanation, Rosie!