Q: What is the percent yield if the theoretical yield of Fe is 137 g and the actual yield is 82.3 g?

$$\displaystyle \frac{82.3}{137} \times 100 = 60.1\%$$

Question 1

Which of the following best describes the greenhouse effect?

Accepted Answer

Greenhouse gases allow sunlight to enter the atmosphere, warm Earth's surface, and trap some of the heat radiated from Earth's surface.

Question 2

Which chemical equation represents the complete combustion of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

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

Question 3

A reaction between 245 g of $$\mathrm{Fe_2O_3}$$ and 131.2 g of CO produces 82.3 g of Fe. What is the limiting reactant?

Accepted Answer

CO

Question 4

Which of the following is a chemical change?

Accepted Answer

Burning gasoline in a car engine

Question 5

What is the percent yield if the theoretical yield of Fe is 137 g and the actual yield is 82.3 g?

Accepted Answer

$$\displaystyle \frac{82.3}{137} 	imes 100 = 60.1\%$$

Question 6

Which balanced equation represents the reaction of lithium metal with water?

Accepted Answer

$$\mathrm{2Li(s) + 2H_2O(l) \rightarrow 2LiOH(aq) + H_2$(g)}$$

Question 7

Which of the following best explains why alkali metals react explosively with water?

Accepted Answer

The reaction is highly exothermic, producing heat that ignites the hydrogen gas formed.

Question 8

Which of the following is the correct balanced equation for the reaction between aluminum metal and fluorine gas?

Accepted Answer

$$\mathrm{2Al(s) + 3F_2(g) \rightarrow 2AlF_3(s)}$$

Question 9

Which of the following statements about halogens is correct?

Accepted Answer

Halogens have ns$$^2np$^5$$ outer electron configurations and tend to form 1- anions.

Question 10

Given the reaction $$\mathrm{2C_8H_{18}(l) + 25O_2(g) \rightarrow 16CO_2(g) + 18H_2O(g)}$$, what is the mole ratio of $$\mathrm{O_2$} to$$ $$\mathrm{CO_2$}$$?

Accepted Answer

$$\displaystyle \frac{25}{16}$$

Question 11

Which of the following is a correct description of a limiting reactant?

Accepted Answer

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

Question 12

What is the theoretical yield of ammonia ($$\mathrm{NH_3$}) in kg $$that can be synthesized from 2.34 kg of $$\mathrm{H_2$}$$ and 25.6 kg of $$\mathrm{N_2$}$$? (Use $$\mathrm{3H_2(g) + N_2$(g) \rightarrow 2NH_3(g)}$$; molar masses: $$\mathrm{H_2$} = 2.02 g/$$mol, $$\mathrm{N_2$} = 28.0 g/$$mol, $$\mathrm{NH_3$} = 17.0 g/$$mol)

Accepted Answer

13.2 kg (from $$\mathrm{H_2$}$$, the limiting reactant)

Question 13

Which of the following is a product of the complete combustion of a hydrocarbon?

Accepted Answer

$$\mathrm{CO_2$}$$ and $$\mathrm{H_2O}$$

Question 14

Which of the following best describes a physical change?

Accepted Answer

A change that alters only the state or appearance, but not the composition.

Question 15

Which equation represents the reaction between hydrogen gas and bromine liquid to form hydrogen bromide?

Accepted Answer

$$\mathrm{H_2$(g) + Br_2$(l) \rightarrow 2HBr(g)}$$

Question 16

If 3.26 g of $$\mathrm{Mg(OH)_2} is $$used to neutralize stomach acid ($$\mathrm{HCl}$$), what is the first step in calculating the mass of $$\mathrm{HCl}$$ neutralized?

Accepted Answer

Convert grams of $$\mathrm{Mg(OH)_2} to $$moles using its molar mass.

Question 17

Which of the following is a correct balanced equation for the reaction between aqueous lead(II) nitrate and aqueous potassium phosphate?

Accepted Answer

$$\mathrm{3Pb(NO_3$)_2(aq) + 2K_3PO_4(aq) \rightarrow Pb_3$(PO_4$)_2(s) + 6KNO_3(aq)}$$

Chemical Reactions and Chemical Quantities: Combustion, Stoichiometry, and Reactivity

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