posted by afdsfd .
what is the maximum number of grams of PH3 that can be formed when 6.2grams of phosphorus reacts with 4.0 grams of hydrogen to form PH3?
How many moles is 6.2 grams of P?
How many moles is 4grams of H2?
Notice in the balanced reaction it takes 1.5 moles of H2 for every one mole of P.
If you have more of H than that, then the limiting reactant is P, otherwise the limiting reactant is H2.
Use the moles of the limiting reactant to determine the moles of PH3.