The percent yield of a reaction is calculated using the formula:

Percent Yield
=
Actual Yield
Theoretical Yield
×
100
Percent Yield=Theoretical YieldActual Yield​×100

Given in the problem:

Actual Yield = 2.13 g
Theoretical Yield = 2.5 g
Substituting these values into the formula:

Percent Yield
=
2.13

g
2.5

g
×
100
=

(2.13/2.5) x 100 = 85.2%

Therefore, the percent yield of the reaction is 85.2%.