RPAL Percent Yield 3

Question 1

For a reaction producing aspirin, if the theoretical yield is 3.00 g and 2.64 g is collected, what is the percent yield?

Accepted Answer

88%

Answer

(2.64 / 3.00) × 100% = 88% yield.

Question 2

A reaction yields 0.45 mol of product but the theoretical yield is 0.50 mol. What is the percent yield?

Accepted Answer

90%

Answer

(0.45 / 0.50) × 100% = 90%; percent yield can be calculated using moles as well as grams.

Question 3

Which of the following is a common source of percent yield less than 100% in lab experiments?

Accepted Answer

Product left on glassware during transfer

Answer

Product sticking to glassware during transfer is a frequent mechanical loss that lowers actual yield.

Question 4

If a reaction has multiple steps, each with 90% yield, what is the overall yield after two steps?

Accepted Answer

81%

Answer

Overall yield = 90% × 90% = 0.9 × 0.9 = 0.81 = 81%; yields multiply across steps.

Question 5

A reaction with a theoretical yield of 10 g gives only 2 g of product. What is the percent yield, and how might a chemist improve it?

Accepted Answer

20%; improve by minimizing side reactions and product loss

Answer

(2/10) × 100% = 20%, which is poor; improvement requires identifying and suppressing side reactions and improving product isolation.

RPAL - Reactants, Products, and Leftovers Practice Test