Question

Determine the percent yield forthe reaction between 82.4 g of Rband 11.6 g of O2 if 39.7 g of Rb2Ois produced

Answer 1

Step 1

The reaction is written and balanced:

4 Rb + O2 =>2 Rb2O

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Step 2

Define % yield of product (Rb2O) = (Actual yield/Theoretical yield) x 100

The actual yield is provided by the exercise = 39.7 g

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Step 3

Determine the limiting reactant. The molar masses are needed to solve this:

For Rb) 85.4 g/mol

For O2) 32 g/mol

Procedure:

4 Rb + O2 =>2 Rb2O

4 x 85.4 g Rb ----- 32 g O2

82.4 g Rb ----- X = 7.72 g O2 are needed

For 82.4 g Rb, 7.72 g O2 is needed, but there is 11.6 g O2. Therefore, O2 is the excess agent. Rb is the limiting reactant.

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Step 4

Determine the theoretical yield from the limiting reactant:

The molar mass Rb2O) 187 g/mol

Procedure:

4 x 85.4 g Rb ------ 2 x 187 g Rb2O

82.4 g Rb ------ X = 90.2 g Rb2O = Theoretical yield

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Step 5

% yield = Actual y./Theoretical y. x 100 = (39.7 g/90.2 g) x 100 = 44 % approx.

Answer: % yield = 44 %