Chem I   Worksheet #31   percent yield                                                  Name_____________________________

Text Reference pgs 293-294

Vocabulary: theoretical yield, actual yield, percent yield

Summary: The percent yield for a reaction is the actual yield (actual amount of product produced in an experiment) divided by the theoretical yield (amount of product expected from calculation).  This is rarely 100% because of side reactions and incomplete reactions. 

 

  1. What is the actual yield of a reaction? What is the percent yield of a reaction? How do the actual yield and the percent yield differ from the theoretical yield?

 

 

 

 

 

  1. According to her pre-lab stoichiometric calculation, a student’s lab experiment should have produced 5.51 g of NaCl. While actually doing the experiment, this student obtained only 4.32 g of NaCl. What was her percent yield?

 

 

 

 

 

  1. Explain why the actual yield for a reaction may be less than the theoretical yield.

 

 

 

 

 

  1. A student calculated the theoretical yield of BaSO4(s) in a precipitation

      experiment to be 1.352 g. When she filtered, dried, and weighed her precipitation,

      however, her yield was only 1.279 g. Calculate the student’s percent yield.

 

 

 

 

 

 

 

  1. Silicon is an element that is found in many rocks ( “silicates”) and is very much in demand in the pure elemental form for the semiconductor industry. Relatively pure silicon can be made from ordinary sand, by reaction with carbon at high temperatures.           

SiO2(s) +   C(s) ŕ   Si(s) +  CO(g)      (unbalanced)

What is the theoretical yield of pure elemental silicon when 100. kg of sand (SiO2) is heated in a suitable furnace with 100. kg of carbon? What is the percent yield if only 17.2 kg of silicon actually results from the process?