Q: What is the percent yield if the actual yield of a product is 19.0 g and the theoretical yield is 22.0 g?

$$\displaystyle \frac{19.0}{22.0} \times 100\% = 86.4\%$$

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 statement best describes the Law of Conservation of Mass as it applies to chemical reactions?

Accepted Answer

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

Question 2

Consider the unbalanced reaction: $$\mathrm{NH_3$(g) + O_2$(g) \rightarrow NO(g) + H_2O(g)}. $$What is the correct stoichiometric coefficient in front of $$\mathrm{O_2$}$$ when the equation is balanced?

Accepted Answer

2

Question 3

Methane combusts according to the balanced equation: $$\mathrm{CH_4$(g) + 2O_2(g) \rightarrow CO_2$(g) + 2H_2O(g)}. If $$you have 5 mol of $$\mathrm{CH_4$}$$ and 8 mol of $$\mathrm{O_2$}$$, which is the limiting reactant?

Accepted Answer

$$\mathrm{O_2$}$$

Question 4

A reaction mixture contains 42.5 g of Mg and 33.8 g of $$\mathrm{O_2$}. $$The balanced equation is $$2\mathrm{Mg(s) + O_2$(g) \rightarrow 2MgO(s)}. $$What is the theoretical yield of $$\mathrm{MgO} in $$grams?

Accepted Answer

70.5 g

Question 5

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

Accepted Answer

The reactant that is completely consumed and determines the amount of product formed.

Question 6

In the reaction $$\mathrm{6CO_2(g) + 6H_2O(l) \rightarrow 6O_2(g) + C_6H_{12}O_6$(aq)}$$, how many grams of glucose ($$\mathrm{C_6H_{12}O_6$}) $$are produced from 3.50 g of $$\mathrm{CO_2$}$$? (Molar mass of $$\mathrm{CO_2$} = 44.0 g/$$mol, $$\mathrm{C_6H_{12}O_6$} = 180.0 g/$$mol)

Accepted Answer

2.39 g

Question 7

A capsule contains 3.26 g of $$\mathrm{Mg(OH)_2} to $$neutralize stomach acid ($$\mathrm{HCl}). $$The balanced equation is $$\mathrm{Mg(OH)_2(s) + 2HCl(aq) \rightarrow 2H_2O(l) + $$MgCl_2$$(aq)}. $$What mass of $$\mathrm{HCl} (in g) is $$neutralized? (Molar mass $$\mathrm{Mg(OH)_2} = 58.3 g/$$mol, $$\mathrm{HCl} = 36.5 g/$$mol)

Accepted Answer

4.08 g

Question 8

What is the percent yield if the actual yield of a product is 19.0 g and the theoretical yield is 22.0 g?

Accepted Answer

$$\displaystyle \frac{19.0}{22.0} 	imes 100\% = 86.4\%$$

Question 9

In the reaction $$\mathrm{$$MnO_2$$ + 4Al \rightarrow 3Mn + 2Al_2O_3}$$, what mass of Al (in grams) is required to completely react with 25.0 g of $$\mathrm{$$MnO_2$$}$$? (Molar mass $$\mathrm{$$MnO_2$$} = 86.9 g/$$mol, Al = 27.0 g/mol)

Accepted Answer

7.75 g

Question 10

A reaction mixture contains 55.0 g of Na and 67.2 g of $$\mathrm{Cl_2$}. $$The balanced equation is $$2\mathrm{Na(s) + Cl_2$(g) \rightarrow 2NaCl(s)}. $$What is the theoretical yield of $$\mathrm{NaCl} in $$grams? (Molar mass Na = 23.0 g/mol, $$\mathrm{Cl_2$} = 70.9 g/$$mol, NaCl = 58.5 g/mol)

Accepted Answer

140.3 g

Question 11

Which of the following is NOT provided by a chemical equation?

Accepted Answer

The speed at which the reaction occurs

Question 12

In the reaction $$\mathrm{$$TiO_2$$(s) + 2C(s) \rightarrow Ti(s) + 2CO(g)}$$, if the percent yield is 85% and you want to produce 375 g of Ti, how much $$\mathrm{$$TiO_2$$} (in $$grams) is required? (Molar mass $$\mathrm{Ti} = 48 g/$$mol, $$\mathrm{$$TiO_2$$} = 80 g/$$mol)

Accepted Answer

882 g

Question 13

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 14

Which of the following is true about balancing chemical equations?

Accepted Answer

Coefficients are changed to balance the equation, not the subscripts.

Question 15

In a reaction, if one reactant is present in a quantity greater than required, what is it called?

Accepted Answer

Excess reactant

Question 16

For the reaction $$2\mathrm{C_2H_6(g) + 7O_2(g) \rightarrow 4CO_2(g) + 6H_2O(g)}$$, how many moles of $$\mathrm{O_2$}$$ are needed to react with 0.248 moles of $$\mathrm{C_2H_6}$$?

Accepted Answer

0.868 mol

Question 17

Which of the following is a correct description of theoretical yield?

Accepted Answer

The amount of product expected based on the limiting reactant.

Question 18

In the reaction $$\mathrm{$$HCO_3$$^- (aq) + H^+ (aq) \rightarrow CO_2$ (g) + H_2O (aq)}$$, what is the state of $$\mathrm{CO_2$}$$?

Accepted Answer

Gas

Question 19

Which of the following is the correct balanced equation for the reaction of lead(II) nitrate and potassium chloride to form lead(II) chloride and potassium nitrate?

Accepted Answer

$$\mathrm{Pb(NO_3$)_2(aq) + 2KCl(aq) \rightarrow $$PbCl_2$$(s) + 2KNO_3(aq)}$$

Chapter 4: Chemical Reactions and Quantities – Study Notes

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