Q: Which formula is used to calculate percent yield?

$\displaystyle \frac{\text{actual yield}}{\text{theoretical yield}} \times 100$

Question 1

In the reaction $\mathrm{N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)}$, if you start with $3.0$ mol $\mathrm{N_2}$ and $6.0$ mol $\mathrm{H_2}$, how many moles of $\mathrm{NH_3}$ can be produced?

Accepted Answer

$4.0$ mol $\mathrm{NH_3}$

Question 2

Which statement best describes the limiting reagent in a chemical reaction?

Accepted Answer

It is the reactant that can make the fewest moles of product.

Question 3

Given the reaction $\mathrm{2H_2(g) + O_2(g) \rightarrow 2H_2O(g)}$, if you have $7.5$ mol $\mathrm{H_2}$ and $47$ mol $\mathrm{O_2}$, what is the limiting reagent?

Accepted Answer

$\mathrm{H_2}$

Question 4

If $75$ mol $\mathrm{H_2O}$ is produced in the above reaction, what is the mass of $\mathrm{H_2O}$ formed? ($\mathrm{M_{H_2O}} = 18.0\ g/mol$)

Accepted Answer

$900\ g$

Question 5

You collect $800\ g$ of $\mathrm{H_2O}$ from the reaction above. What is the percent yield?

Accepted Answer

$89\%$

Question 6

What is the percent by mass of nitrogen in calcium nitrate, $\mathrm{Ca(NO_3)_2}$? ($\mathrm{M_{Ca(NO_3)_2}} = 164.1\ g/mol$, $\mathrm{M_N} = 14.0\ g/mol$)

Accepted Answer

$17.1\%$

Question 7

A reaction produces $4.0$ mol $\mathrm{NH_3}$, which has a molar mass of $17.0\ g/mol$. What is the theoretical yield in grams?

Accepted Answer

$68\ g$

Question 8

If the actual yield of $\mathrm{NH_3}$ is $52\ g$ and the theoretical yield is $68\ g$, what is the percent yield?

Accepted Answer

$76\%$

Question 9

In the reaction $\mathrm{TiCl_4 + 2Cl_2 \rightarrow TiCl_4}$, if you start with $0.0423$ mol $\mathrm{Ti}$ and $0.0846$ mol $\mathrm{Cl_2}$, how many moles of $\mathrm{TiCl_4}$ can be formed?

Accepted Answer

$0.0423$ mol

Question 10

If $8.02\ g$ of $\mathrm{TiCl_4}$ is the theoretical yield and $7.7\ g$ is collected, what is the percent yield?

Accepted Answer

$96\%$

Question 11

Given $1.50\ kg$ of $\mathrm{Al_2O_3}$ ($\mathrm{M_{Al_2O_3}} = 102\ g/mol$), how many moles of $\mathrm{Al_2O_3}$ is this?

Accepted Answer

$14.7$ mol

Question 12

If $3.93\ kg$ of $\mathrm{AlCl_3}$ is the theoretical yield and $2.85\ kg$ is collected, what is the percent yield?

Accepted Answer

$72.6\%$

Question 13

In a combustion reaction, why is the hydrocarbon almost always the limiting reagent?

Accepted Answer

Because oxygen is usually present in excess

Question 14

For the reaction $\mathrm{4C_4H_{10} + 13O_2 \rightarrow 8CO_2 + 10H_2O}$, how many moles of $\mathrm{CO_2}$ are produced from $4$ mol $\mathrm{C_4H_{10}}$?

Accepted Answer

$16$ mol

Question 15

Which of the following steps is NOT necessary when solving a limiting reagent problem?

Accepted Answer

Use the reactant in excess to determine the amount of product

Question 16

A student mixes $2.0$ mol $\mathrm{H_2}$ and $32.0$ mol $\mathrm{O_2}$ to produce water. What is the theoretical yield of $\mathrm{H_2O}$ in moles?

Accepted Answer

$2.0$ mol

Question 17

If a reaction has no limiting reagent, what does this imply about the reactants?

Accepted Answer

They are present in stoichiometric proportions

Question 18

Which formula is used to calculate percent yield?

Accepted Answer

$\displaystyle \frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100$

Stoichiometry, Limiting Reactants, and Percent Yield in General Chemistry

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