Q: Which of the following is the correct formula to calculate the percent yield of a reaction?

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

Question 1

Which of the following best describes a combustion reaction?

Accepted Answer

A reaction in which a substance reacts with oxygen to form one or more oxygen-containing compounds and emits heat.

Question 2

Given the unbalanced equation $$\mathrm{C_3H_8 + O_2$ \rightarrow CO_2$ + H_2O}$$, what is the correct set of coefficients to balance the equation?

Accepted Answer

$$1, 5, 3, 4$$

Question 3

Which of the following statements about balancing chemical equations is correct?

Accepted Answer

The total number of atoms for each element must be the same on both sides of the equation.

Question 4

In the reaction $$2\mathrm{C_8H_{18}(l)} + 25\mathrm{O_2$(g)} \rightarrow 16\mathrm{CO_2$(g)} + 18\mathrm{H_2O(g)}$$, how many moles of $$\mathrm{CO_2$}$$ are produced from 5.00 moles of $$\mathrm{C_8H_{18}}$$?

Accepted Answer

$$40.0$$ moles

Question 5

A student mixes two aqueous solutions and observes the formation of a solid. What type of reaction has most likely occurred?

Accepted Answer

Precipitation reaction

Question 6

Which of the following is the correct formula to calculate the percent yield of a reaction?

Accepted Answer

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

Question 7

If 1.00 g of $$\mathrm{C_8H_{18}} ($$molar mass $$114.224\ \mathrm{g/mol}) is $$combusted, what mass of $$\mathrm{H_2O} ($$molar mass $$18.016\ \mathrm{g/mol}) is $$produced? Use the reaction: $$2\mathrm{C_8H_{18}(l)} + 25\mathrm{O_2$(g)} \rightarrow 16\mathrm{CO_2$(g)} + 18\mathrm{H_2O(g)}.$$

Accepted Answer

$$1.42\ \mathrm{g}$$

Question 8

Which reactant is the limiting reactant in a reaction?

Accepted Answer

The reactant that produces the smallest amount of product.

Question 9

A reaction has a theoretical yield of $$12.74\ \mathrm{g}$$ $$\mathrm{CO_2$}$$, but only $$10.01\ \mathrm{g}$$ $$\mathrm{CO_2$} is $$produced. What is the percent yield?

Accepted Answer

$$78.57\%$$

Question 10

Which of the following best describes the law of conservation of mass as it applies to chemical reactions?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 11

In the reaction $$2\mathrm{C_8H_{18}(l)} + 25\mathrm{O_2$(g)} \rightarrow 16\mathrm{CO_2$(g)} + 18\mathrm{H_2O(g)}$$, how many moles of $$\mathrm{O_2$}$$ are required to completely react with $$4.00$$ moles of $$\mathrm{C_8H_{18}}$$?

Accepted Answer

$$50.0$$ moles

Question 12

Which of the following is NOT a step in solving a limiting reactant problem?

Accepted Answer

Identify which reactant gives the largest mass of product.

Question 13

A reaction is carried out with $$10.0 g of$$ $$\mathrm{A} ($$molar mass $$20.0\ \mathrm{g/mol}) $$and $$15.0 g of$$ $$\mathrm{B} ($$molar mass $$30.0\ \mathrm{g/mol}) $$according to the equation $$A + 2B \rightarrow C. $$Which reactant is limiting?

Accepted Answer

$$\mathrm{B}$$

Question 14

Which of the following is the correct stoichiometric ratio to convert from moles of $$\mathrm{C_8H_{18}} to $$moles of $$\mathrm{CO_2$} in $$the reaction $$2\mathrm{C_8H_{18}} + 25\mathrm{O_2$} \rightarrow 16\mathrm{CO_2$} + 18\mathrm{H_2O}$$?

Accepted Answer

$$\displaystyle \frac{16\ \mathrm{mol}\ \mathrm{CO_2$}}{2\ \mathrm{mol}\ \mathrm{C_8H_{18}}}$$

Question 15

Which of the following best describes a decomposition reaction?

Accepted Answer

A reaction in which a single reactant breaks down into two or more products.

Question 16

Which of the following is the correct sequence for solving a mass-to-mass stoichiometry problem?

Accepted Answer

Mass of reactant $$\rightarrow$$ moles of reactant $$\rightarrow$$ moles of product $$\rightarrow$$ mass of product

Question 17

Which of the following is a combination reaction?

Accepted Answer

$$\mathrm{N_2$} + 3\mathrm{H_2$} \rightarrow 2\mathrm{NH_3$}$$

Question 18

If $$22.0$$ moles of $$\mathrm{C_8H_{18}}$$ are burned, how many moles of $$\mathrm{H_2O}$$ are produced according to $$2\mathrm{C_8H_{18}} + 25\mathrm{O_2$} \rightarrow 16\mathrm{CO_2$} + 18\mathrm{H_2O}$$?

Accepted Answer

$$198$$ moles

Chapter 4: Chemical Reactions and Chemical Quantities – Study Notes

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