Hi,
I am working on stoichiometry and limiting reactant problems. I have worked through examples in my book and I did them right and can solve for the excess, however there is one problem in the book that has confused me. I don't understand why they identified the limiting reactant as the one they did.
Equation
S8+4Cl2------4S2Cl2
200g of sulfur reacts with 100g of chlorine, what mass of disulfur dichloride is produced?
100g Cl2 *1mol cl2/70.91gcl2=1.410 mol Cl2
200g S2*1mol S8/256.5gS8=0.7797 mol S8
Isn't Sulfur the limiting reactant??? My book says its chlorine but I don't see how that is possible.
Someone please explain this to me. I thought the smaller number is the limiting reactant but it appears its not the case here.
To determine the limiting reactant in a stoichiometry problem like this, you need to compare the number of moles of each reactant to the stoichiometric ratio established by the balanced equation.
In this case, you correctly calculated the number of moles of chlorine (Cl2) as 1.410 mol. And you correctly calculated the number of moles of sulfur (S8) as 0.7797 mol.
To find the limiting reactant, compare the ratio of moles of each reactant to the ratio of moles of reactants in the balanced equation. The balanced equation tells us that 1 mole of S8 reacts with 4 moles of Cl2 to produce 4 moles of S2Cl2.
So, for every 1 mole of S8, we need 4 moles of Cl2. Therefore, the stoichiometric ratio of the reactants is 1:4 (S8:Cl2).
In this case, since you have 0.7797 mol of S8 and 1.410 mol of Cl2, you have an excess of Cl2 because the ratio is greater than 1:4. Therefore, chlorine (Cl2) is the excess reactant, and sulfur (S8) is the limiting reactant.
To determine the mass of disulfur dichloride produced, you need to use the limiting reactant to calculate the theoretical yield.
Using the moles of the limiting reactant (0.7797 mol S8), you can determine the moles of disulfur dichloride (S2Cl2) produced using the stoichiometric ratio of the balanced equation (4 moles S2Cl2 / 1 mole S8).
Then, convert the moles of disulfur dichloride to grams using the molar mass of S2Cl2 (which is obtained from the atomic masses of sulfur and chlorine).
Hope this explanation helps you understand why chlorine (Cl2) is identified as the limiting reactant in this particular problem.