Q: Which of the following is the correct formula for the percent yield of a chemical reaction?

$$\text{Percent yield} = \dfrac{\text{actual yield}}{\text{theoretical yield}} \times 100$$

Q: Which of the following is a correct mole-to-mole ratio from the balanced equation $$2\mathrm{C}_8\mathrm{H}_{18}(l) + 25\mathrm{O}_2(g) \rightarrow 16\mathrm{CO}_2(g) + 18\mathrm{H}_2O(g)$$?

$$\dfrac{25\text{ mol }\mathrm{O}_2}{2\text{ mol }\mathrm{C}_8\mathrm{H}_{18}}$$

Question 1

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

Accepted Answer

The total mass of reactants must equal the total mass of products.

Question 2

What is the balanced chemical equation for the combustion of methane?

Accepted Answer

$$\mathrm{CH}_4(g) + 2\mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g) + 2\mathrm{H}_2O(g)$$

Question 3

In the reaction $$4\mathrm{FeCO}_3(s) + \mathrm{O}_2(g) \rightarrow 2\mathrm{Fe}_2\mathrm{O}_3(s) + 4\mathrm{CO}_2(g)$$, how many oxygen atoms are present on the right-hand side?

Accepted Answer

10

Question 4

Which of the following must always be the same on both sides of a balanced chemical equation?

Accepted Answer

The number of atoms of each kind

Question 5

A student burns 22.0 moles of octane ($$\mathrm{C}_8\mathrm{H}_{18}) $$according to the equation $$2\mathrm{C}_8\mathrm{H}_{18}(l) + 25\mathrm{O}_2(g) \rightarrow 16\mathrm{CO}_2(g) + 18\mathrm{H}_2O(g). $$How many moles of water are produced?

Accepted Answer

198 moles

Question 6

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 7

If 37.8 g of $$\mathrm{CO}_2$$ are consumed in photosynthesis ($$6\mathrm{CO}_2(g) + 6\mathrm{H}_2O(l) \rightarrow 6\mathrm{O}_2(g) + \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6(aq)$$), what mass of glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6) $$can be synthesized? (Molar masses: $$\mathrm{CO}_2 = 44.01 g/$$mol, $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 = 180.2 g/$$mol)

Accepted Answer

25.8 g

Question 8

Which reactant is the limiting reactant when 42.5 g of Mg and 33.8 g of $$\mathrm{O}_2$$ are mixed according to $$2\mathrm{Mg}(s) + \mathrm{O}_2(g) \rightarrow 2\mathrm{MgO}(s)$$? (Molar masses: Mg = 24.31 g/mol, $$\mathrm{O}_2 = 32.00 g/$$mol)

Accepted Answer

Mg

Question 9

What is the percent yield if 195 g of NaBr is produced when 84.7 g of sodium is combined with 175.0 g of bromine according to $$2\mathrm{Na}(s) + \mathrm{Br}_2(l) \rightarrow 2\mathrm{NaBr}(s)$$, and the theoretical yield is 218 g?

Accepted Answer

89.4%

Question 10

Which of the following is true about the limiting reactant in a chemical reaction?

Accepted Answer

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

Question 11

In the reaction $$3\mathrm{NO}_2(g) + \mathrm{H}_2O(l) \rightarrow 2\mathrm{HNO}_3(l) + \mathrm{NO}(g)$$, if 5 mol $$\mathrm{NO}_2$$ and 1 mol $$\mathrm{H}_2O$$ are combined and react completely, how many moles of the reactant in excess remain after the reaction?

Accepted Answer

2 mol $$\mathrm{NO}_2$$

Question 12

Which of the following is the correct formula for the percent yield of a chemical reaction?

Accepted Answer

$$	ext{Percent yield} = \dfrac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100$$

Question 13

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

Accepted Answer

They indicate the relative number of moles of each substance involved in the reaction.

Question 14

Which of the following is a correct mole-to-mole ratio from the balanced equation $$2\mathrm{C}_8\mathrm{H}_{18}(l) + 25\mathrm{O}_2(g) \rightarrow 16\mathrm{CO}_2(g) + 18\mathrm{H}_2O(g)$$?

Accepted Answer

$$\dfrac{25	ext{ mol }\mathrm{O}_2}{2	ext{ mol }\mathrm{C}_8\mathrm{H}_{18}}$$

Question 15

Which of the following is a correct balanced equation for the reaction between aqueous strontium chloride and aqueous lithium phosphate to form solid strontium phosphate and aqueous lithium chloride?

Accepted Answer

$$3\mathrm{SrCl}_2(aq) + 2\mathrm{Li}_3\mathrm{PO}_4(aq) \rightarrow \mathrm{Sr}_3(\mathrm{PO}_4)_2(s) + 6\mathrm{LiCl}(aq)$$

Question 16

Which of the following is a characteristic of alkali metal reactions with water?

Accepted Answer

They become more vigorous as you move down the group.

Question 17

Which of the following is the correct balanced equation for the reaction of iron with chlorine to form iron(III) chloride?

Accepted Answer

$$2\mathrm{Fe}(s) + 3\mathrm{Cl}_2(g) \rightarrow 2\mathrm{FeCl}_3(s)$$

Chemical Reactions and Chemical Quantities: Chapter 4 Study Notes

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