Q: Which of the following is the correct formula for calculating percent yield?

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

Question 1

Which of the following best describes a combustion reaction?

Accepted Answer

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

Question 2

Balance the following equation: $$\mathrm{C_4H_{10}(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}. $$What is the correct set of coefficients?

Accepted Answer

$$2, 13, 8, 10$$

Question 3

In the reaction $$\mathrm{2Co_2O_3(s) + 3C(s) \rightarrow 4Co(s) + 3CO_2(g)}$$, how many moles of carbon are required to completely react with 4 moles of $$\mathrm{Co_2O_3}$$?

Accepted Answer

6 moles

Question 4

Which of the following is the correct balanced equation for the reaction between strontium chloride and lithium phosphate?

Accepted Answer

$$\mathrm{3SrCl_2(aq) + 2Li_3PO_4(aq) \rightarrow Sr_3$(PO_4$)_2(s) + 6LiCl(aq)}$$

Question 5

A sample contains 22.0 moles of $$\mathrm{C_8H_{18}}. $$According to the balanced equation $$\mathrm{2C_8H_{18} + 25O_2 \rightarrow 16CO_2 + 18H_2O}$$, how many moles of $$\mathrm{CO_2$}$$ are produced?

Accepted Answer

176 moles

Question 6

Which reactant is the limiting reactant if 5 molecules of $$\mathrm{CH_4$}$$ and 8 molecules of $$\mathrm{O_2$}$$ are mixed and react according to $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$?

Accepted Answer

$$\mathrm{O_2$}$$

Question 7

A reaction mixture contains 42.5 g Mg and 33.8 g $$\mathrm{O_2$}. $$According to $$\mathrm{2Mg + O_2$ \rightarrow 2MgO}$$, what is the theoretical yield of $$\mathrm{MgO} in $$grams?

Accepted Answer

70.5 g

Question 8

If the actual yield of $$\mathrm{MgO} in $$the previous question is 55.9 g, what is the percent yield?

Accepted Answer

$$79.3\%$$

Question 9

Which of the following best defines the limiting reactant in a chemical reaction?

Accepted Answer

The reactant that determines the maximum amount of product that can be formed.

Question 10

In a real-world scenario, why might the actual yield of a chemical reaction be less than the theoretical yield?

Accepted Answer

Because some product may be lost during handling or side reactions may occur.

Question 11

Which of the following is the correct balanced equation for the combustion of methane?

Accepted Answer

$$\mathrm{CH_4$(g) + 2O_2(g) \rightarrow CO_2$(g) + 2H_2O(g)}$$

Question 12

A plant consumes 37.8 g of $$\mathrm{CO_2$} in $$photosynthesis. How many grams of glucose ($$\mathrm{C_6H_{12}O_6$}$$, molar mass = 180.2 g/mol) can be synthesized? (Balanced equation: $$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2)$$

Accepted Answer

25.8 g

Question 13

Which of the following is a correct description of a chemical equation?

Accepted Answer

It provides the formulas, states, and relative numbers of reactant and product molecules.

Question 14

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

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

Question 15

Which of the following best describes the role of coefficients in a balanced chemical equation?

Accepted Answer

They specify the relative amounts in moles of each substance involved in the reaction.

Question 16

Which of the following is a correct balanced equation for the reaction of potassium metal with bromine gas?

Accepted Answer

$$\mathrm{2K(s) + Br_2$(g) \rightarrow 2KBr(s)}$$

Question 17

Which of the following is the correct balanced equation for the reaction of rubidium metal with water?

Accepted Answer

$$\mathrm{2Rb(s) + 2H_2O(l) \rightarrow 2Rb^+(aq) + 2OH^-(aq) + H_2$(g)}$$

Question 18

Which of the following is the correct balanced equation for the reaction of chlorine gas with solid iodine to form interhalogen compounds?

Accepted Answer

$$\mathrm{Cl_2$(g) + I_2$(s) \rightarrow 2ICl(g)}$$

Chapter 4: Chemical Reactions and Chemical Quantities – Study Notes

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