A friend is doing his chemistry homework and is working with the following chemical reaction.
2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(g)
He tells you that if he reacts 2 moles of C2H2 with 4 moles of O2, then the C2H2 is the limiting reactant since there are fewer moles of C2H2 than O2.
a. How would you explain to him where he went wrong with his reasoning (what concept is he missing)?
b. After providing your friend with the explanation from part a, he still doesn’t believe you because he had a homework problem where 2 moles of calcium were reacted with 4 moles of sulfur and he needed to determine the limiting reactant. The reaction is
Ca(s) + S(s) → CaS(s)
He obtained the correct answer, Ca, by reasoning that since there were fewer moles of calcium reacting, calcium had to be the limiting reactant. How would you explain his reasoning flaw and why he got “lucky” in choosing the answer that he did? Formula Masses and Mole Calculations