Identify the limiting reactant in the reaction of hydrogen and ethylene (c2h4) to form c2h6, of 4.40 g of h2 and 10.5 g of c2h4 are combined. determine the amount (in grams) of excess reactant that remains after the reaction is complete.

Definition :   Limiting reagent is the substance in a chemical reaction that is consumed when chemical reaction is complete.

step 1 :  first write the chemical reaction and then balanced the chemical equation

step 2 :  convert given masses into moles.

step 3 :  Now find the limiting reagent.

Now we conclude that   is the limiting reagent.

step 4 :  Amount of the excess reactant i.e

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

the dissolution of polymer can be thermodynamically described in 2 steps.