Question 1

What is the molar mass of phosphorus pentachloride (PCl5)?

Accepted Answer

A) 177.25 g/mol 
B) 190.30 g/mol 
C) 208.22 g/mol 
D) 172.75 g/mol 
E) 202.82 g/mol

Question 2

One form of elemental sulfur is a ring of eight sulfur atoms. How many moles of molecular oxygen are consumed when one mole of this allotrope burns to make sulfur trioxide?

Accepted Answer

A) 3 
B) 6 
C) 12 
D) 18 
E) 24

Question 3

A reaction vessel contains equal masses of solid magnesium metal and oxygen gas. The mixture is ignited and burns with a burst of light and heat, producing solid MgO. The mass of the MgO is less than the initial mass of the magnesium and oxygen. What is your explanation for this apparent loss of mass?

Accepted Answer

A) Conservation of mass is violated in this reaction. 
B) Some of the mass was converted into energy (heat and light) as  
C) Not all of the oxygen reacted. 
D) Not all of the magnesium reacted. 
E) Measurement must be in error because mass is conserved in chemical reactions.

Question 4

How many atoms of chlorine are there in 25.0 g of calcium chloride (CaCl2)?

Accepted Answer

A) 1.36  1023 atoms 
B) 2.67  1024 atoms 
C) 2.71  1023 atoms 
D) 1.95  1023 atoms

Question 5

A bottle containing 1,665 g of sulfuric acid (H2SO4, 98.08 g/mol) was spilled in a laboratory. The emergency spill kit contained a full 2.0 kg bottle of sodium carbonate (105.99 g/mol). Is this enough sodium carbonate to neutralize the acid, according to the following reaction? H2SO4(aq)  Na2CO3(s)  Na2SO4(aq)  CO2(g)  H2O(l)

Accepted Answer

A) Yes, there is about 50% more than what is needed. 
B) Yes, there is exactly enough sodium carbonate, but no excess. 
C) No, there is not enough sodium carbonate, but the amount is only about 10% too small. 
D) No, there is not nearly enough sodium carbonate. 
E) Yes, but there is only about 10% excess.

Question 6

Write the balanced reaction equation for the combustion of nonane (C₉H₂₀), which is found in gasoline.

Accepted Answer

The answer of Write the balanced reaction equation for the...

Question 7

Some indoor air purification systems work by converting some of the oxygen in the air to ozone. The ozone oxidizes mold, mildew spores, and other biological pollutants. It is claimed that one such system generates 5.0 g of ozone per hour by passing dry air through the purifier at a rate of 5.0 L/min. If 1.0 L of air contains 0.28 g of oxygen, what percent of the O₂ molecules are converted to O₃ molecules?

Accepted Answer

The answer of Some indoor air purification systems work by...

Question 8

You are given a liquid sample that contains either methanol (CH3OH), ethanol (CH3CH2OH), or a mixture of both. You use combustion analysis of a 0.336 g sample and obtain 0.462 g of CO2. What did you learn about your sample?

Accepted Answer

A) It is methanol. 
B) It is ethanol. 
C) It is more methanol than ethanol. 
D) It is more ethanol than methanol. 
E) It contains equal amounts of methanol and ethanol.

Question 9

For a standard airbag, 131 g of sodium azide (65.00 g/mol) is required to generate enough gas to adequately fill the airbag. How many formula units of sodium azide are needed?

Accepted Answer

A) 3.35  10-24 formula units 
B) 1.21  1024 formula units 
C) 7.89  1025 formula units 
D) 1.41  10-20 formula units 
E) 5.13  1027 formula units

Question 10

Which statement about the combustion of propane (C3H8) is not correct? C3H8
    
5O2
    
3CO2
    
4H2O

Accepted Answer

A) For every propane molecule consumed, three molecules of carbon dioxide are produced. 
B) For every two molecules of propane consumed, eight molecules of water are produced. 
C) For every five molecules of oxygen consumed, four molecules of water are produced. 
D) For every three molecules of carbon dioxide produced, five molecules of oxygen are consumed. 
E) For every carbon dioxide molecule produced, four molecules of water are also produced.

Question 11

Glucose (C6H12O6) is oxidized by molecular oxygen to carbon dioxide and water. How many O2 molecules are needed for each molecule of glucose that is oxidized?

Accepted Answer

A) 1 
B) 2 
C) 6 
D) 12 
E) 18

Question 12

Calcium hydride (CaH2) is so reactive with water that it can be used to remove traces of water from solvents other than water. If 24.6 g of calcium hydride is added to a large volume of solvent that contains 14.0 g of water, which of these remains, water or calcium hydride, after the reaction is complete? The reaction is: CaH2(s)  2H2O(l)  Ca(OH)2(s)  2H2(g)

Accepted Answer

A) CaH2 will be left over. 
B) Water will be left over. 
C) Both will be completely consumed. 
D) There is no way to tell.

Question 13

A mass of 11.60 g of phosphoric acid was produced from the reaction of 10.00 g of P4O10 with 12.00 g water. What was the percent yield for this reaction?

Accepted Answer

A) 78.62% 
B) 101.1% 
C) 92.70% 
D) 84.00% 
E) 52.70%

Question 14

Sulfur dioxide from coal-fired power plants combines with water in the atmosphere to produce acid rain. What is the product when one molecule of SO2 reacts with one molecule of water?

Accepted Answer

A) two molecules of sulfurous acid 
B) one sulfate ion 
C) two sulfite ions 
D) one molecule of sulfuric acid 
E) one molecule of sulfurous acid

Question 15

Water can be separated into its elements according to the following equation by electrolysis. If 20.0 g of water is decomposed by this method, how much oxygen gas is produced? 2H2O(l)  2H2(g)  O2(g)

Accepted Answer

A) 17.8 g 
B) 8.9 g 
C) 35.6 g 
D) 16.0 g 
E) 10.0 g

Question 16

The acid-base reaction between phosphoric acid, H3PO4, and calcium hydroxide, Ca(OH)2, yields water and calcium phosphate. For each mole of calcium phosphate produced by this reaction, how many moles of water are produced?

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 6

Question 17

Beryllium metal reacts with chlorine gas to produce beryllium chloride (BeCl2). Given the following diagram of available beryllium atoms and chlorine molecules in a reaction flask, identify the excess reagent and how many atoms/molecules of reactant remain at the end of the reaction.

Accepted Answer

A) Excess reagent: chlorine; Molecules remaining: one 
B) Excess reagent: beryllium; Atoms remaining: one 
C) Excess reagent: chlorine; Molecules remaining: two 
D) Excess reagent: beryllium; Atoms remaining: two 
E) There is no excess reagent in this reaction.

Question 18

U.S. Lime & Minerals is a company that produces quicklime, CaO, by heating calcium hydroxide, Ca(OH)2. What is the percent yield if 45 grams of quicklime are obtained from 1 mole of calcium hydroxide?

Accepted Answer

A) 61% 
B) 80% 
C) 45% 
D) 100% 
E) 90%

Question 19

Fool's Gold is the mineral pyrite (FeS2). What is the mass percent of sulfur in pyrite?

Accepted Answer

A) 36.44% 
B) 46.59% 
C) 49.09% 
D) 53.41% 
E) 63.56%

Question 20

Which one of the following samples contains the largest number of molecules?

Accepted Answer

A) 55 g of H2O 
B) 3 moles of H2O 
C) 3 moles of HF 
D) 62 g of H2O 
E) 62 g of HF

Exam 3: Stoichiometry: Mass, Formulas, and Reactions

What is the molar mass of phosphorus pentachloride (PCl₅) ?

One form of elemental sulfur is a ring of eight sulfur atoms. How many moles of molecular oxygen are consumed when one mole of this allotrope burns to make sulfur trioxide?

How many atoms of chlorine are there in 25.0 g of calcium chloride (CaCl₂) ?

Write the balanced reaction equation for the combustion of nonane (C₉H₂₀), which is found in gasoline.

You are given a liquid sample that contains either methanol (CH₃OH) , ethanol (CH₃CH₂OH) , or a mixture of both. You use combustion analysis of a 0.336 g sample and obtain 0.462 g of CO₂. What did you learn about your sample?

For a standard airbag, 131 g of sodium azide (65.00 g/mol) is required to generate enough gas to adequately fill the airbag. How many formula units of sodium azide are needed?

Which statement about the combustion of propane (C₃H₈) is not correct? C₃H₈ 5O₂ 3CO₂ 4H₂O

Glucose (C₆H₁₂O₆) is oxidized by molecular oxygen to carbon dioxide and water. How many O₂ molecules are needed for each molecule of glucose that is oxidized?

A mass of 11.60 g of phosphoric acid was produced from the reaction of 10.00 g of P₄O₁₀with 12.00 g water. What was the percent yield for this reaction?

Sulfur dioxide from coal-fired power plants combines with water in the atmosphere to produce acid rain. What is the product when one molecule of SO₂ reacts with one molecule of water?

Water can be separated into its elements according to the following equation by electrolysis. If 20.0 g of water is decomposed by this method, how much oxygen gas is produced? 2H₂O(l) 2H₂(g) O₂(g)

The acid-base reaction between phosphoric acid, H₃PO₄, and calcium hydroxide, Ca(OH) ₂, yields water and calcium phosphate. For each mole of calcium phosphate produced by this reaction, how many moles of water are produced?

Beryllium metal reacts with chlorine gas to produce beryllium chloride (BeCl₂) . Given the following diagram of available beryllium atoms and chlorine molecules in a reaction flask, identify the excess reagent and how many atoms/molecules of reactant remain at the end of the reaction.

U.S. Lime & Minerals is a company that produces quicklime, CaO, by heating calcium hydroxide, Ca(OH) ₂. What is the percent yield if 45 grams of quicklime are obtained from 1 mole of calcium hydroxide?

Fool's Gold is the mineral pyrite (FeS₂) . What is the mass percent of sulfur in pyrite?

Which one of the following samples contains the largest number of molecules?

Exam 3: Stoichiometry: Mass, Formulas, and Reactions

What is the molar mass of phosphorus pentachloride (PCl5) ?

One form of elemental sulfur is a ring of eight sulfur atoms. How many moles of molecular oxygen are consumed when one mole of this allotrope burns to make sulfur trioxide?

How many atoms of chlorine are there in 25.0 g of calcium chloride (CaCl2) ?

Write the balanced reaction equation for the combustion of nonane (C9H20), which is found in gasoline.

You are given a liquid sample that contains either methanol (CH3OH) , ethanol (CH3CH2OH) , or a mixture of both. You use combustion analysis of a 0.336 g sample and obtain 0.462 g of CO2. What did you learn about your sample?

For a standard airbag, 131 g of sodium azide (65.00 g/mol) is required to generate enough gas to adequately fill the airbag. How many formula units of sodium azide are needed?

Which statement about the combustion of propane (C3H8) is not correct? C3H8 5O2 3CO2 4H2O

Glucose (C6H12O6) is oxidized by molecular oxygen to carbon dioxide and water. How many O2 molecules are needed for each molecule of glucose that is oxidized?

A mass of 11.60 g of phosphoric acid was produced from the reaction of 10.00 g of P4O10 with 12.00 g water. What was the percent yield for this reaction?

Sulfur dioxide from coal-fired power plants combines with water in the atmosphere to produce acid rain. What is the product when one molecule of SO2 reacts with one molecule of water?

Water can be separated into its elements according to the following equation by electrolysis. If 20.0 g of water is decomposed by this method, how much oxygen gas is produced? 2H2O(l) 2H2(g) O2(g)

The acid-base reaction between phosphoric acid, H3PO4, and calcium hydroxide, Ca(OH) 2, yields water and calcium phosphate. For each mole of calcium phosphate produced by this reaction, how many moles of water are produced?

Beryllium metal reacts with chlorine gas to produce beryllium chloride (BeCl2) . Given the following diagram of available beryllium atoms and chlorine molecules in a reaction flask, identify the excess reagent and how many atoms/molecules of reactant remain at the end of the reaction.

U.S. Lime & Minerals is a company that produces quicklime, CaO, by heating calcium hydroxide, Ca(OH) 2. What is the percent yield if 45 grams of quicklime are obtained from 1 mole of calcium hydroxide?

Fool's Gold is the mineral pyrite (FeS2) . What is the mass percent of sulfur in pyrite?

Which one of the following samples contains the largest number of molecules?

What is the molar mass of phosphorus pentachloride (PCl₅) ?

How many atoms of chlorine are there in 25.0 g of calcium chloride (CaCl₂) ?

Write the balanced reaction equation for the combustion of nonane (C₉H₂₀), which is found in gasoline.

You are given a liquid sample that contains either methanol (CH₃OH) , ethanol (CH₃CH₂OH) , or a mixture of both. You use combustion analysis of a 0.336 g sample and obtain 0.462 g of CO₂. What did you learn about your sample?

Which statement about the combustion of propane (C₃H₈) is not correct? C₃H₈ 5O₂ 3CO₂ 4H₂O

Glucose (C₆H₁₂O₆) is oxidized by molecular oxygen to carbon dioxide and water. How many O₂ molecules are needed for each molecule of glucose that is oxidized?

A mass of 11.60 g of phosphoric acid was produced from the reaction of 10.00 g of P₄O₁₀with 12.00 g water. What was the percent yield for this reaction?

Sulfur dioxide from coal-fired power plants combines with water in the atmosphere to produce acid rain. What is the product when one molecule of SO₂ reacts with one molecule of water?

Water can be separated into its elements according to the following equation by electrolysis. If 20.0 g of water is decomposed by this method, how much oxygen gas is produced? 2H₂O(l) 2H₂(g) O₂(g)

The acid-base reaction between phosphoric acid, H₃PO₄, and calcium hydroxide, Ca(OH) ₂, yields water and calcium phosphate. For each mole of calcium phosphate produced by this reaction, how many moles of water are produced?

Beryllium metal reacts with chlorine gas to produce beryllium chloride (BeCl₂) . Given the following diagram of available beryllium atoms and chlorine molecules in a reaction flask, identify the excess reagent and how many atoms/molecules of reactant remain at the end of the reaction.

U.S. Lime & Minerals is a company that produces quicklime, CaO, by heating calcium hydroxide, Ca(OH) ₂. What is the percent yield if 45 grams of quicklime are obtained from 1 mole of calcium hydroxide?

Fool's Gold is the mineral pyrite (FeS₂) . What is the mass percent of sulfur in pyrite?