What is the theoretical yield of ethyl chloride in the reaction of 20.2 g of ethylene with 53 g of hydrogen chloride? (For ethylene, 28 amu; for hydrogen chloride,36.5amu ; for ethyl chloride, 64.5 amu.) What is the percent yield if 23.5g of ethyl chloride is actually formed?

Answer 1

This is a limiting reagent problem. How do I know that? Because amounts for BOTH reactants are given.
Write the equation and balance it.
2a. Convert 20.2 g ethylene to mols. mols = grams/molar mass.
2b. Do the same for HCl.

3a. Using the coefficient in the balanced equation, convert mols ethylene from 2a to mols ethyl chloride.
3b. Do the same for HCl
3c. You will obtain different answers for mols ethyl chloride; of course, one of those must be wrong. The correct answer in limiting reagent problems is ALWAYS the smaller one and the reactant producing that value is the limiting reagent.

4. Using the smaller number to convert to grams. g = mols x molar mass. This is the theoretical yield.

5. %yield = (actual yield/theoretical yield)(100 = ??