Deck 7: Stoichiometry-Mass Relationships and Chemical Reactions

Question 1

One mole is defined as __________

A)the number of particles equal to the number of atoms in exactly 12 g of carbon-12.
B)the number of particles equal to the number of atoms in exactly 16 g of oxygen-16.
C)the number of particles equal to the number of molecules in 1kg of water.
D)the number of particles equal to the number of atoms in exactly 1 g of hydrogen-1.
E)the number of particles equal to the number of atoms in exactly 1 kg of carbon at the National Bureau of Standards.

Answer 1

the number of particles equal to the number of atoms in exactly 12 g of carbon-12.

Question 2

Which statement about a balanced chemical reaction equation is always correct?

A)The total number of moles of the products equals the total number of moles of the reactants.
B)The number of atoms of each kind is the same for the products as for the reactants.
C)The sum of the stoichiometric coefficients for the products equals the sum of the stoichiometric coefficients for the reactants.
D)The sum of the masses of all gaseous products equals the sum of the masses of the gaseous reactants.
E)The sum of the masses of solid products equals the sum of the masses of solid reactants.

Answer 2

The number of atoms of each kind is the same for the products as for the reactants.

Question 3

Hydrogen peroxide decomposes to produce water and oxygen.Which relationship regarding the quantities of reactants and products associated with this reaction is NOT correct? 2 H₂O₂( ) $\to$ 2 H₂O( )+ O₂(g)

A)2 molecules $\to$ 2 molecules + 1 molecule
B)2 mol $\to$ 2 mol + 1 mol
C)68.0 g $\to$ 36.0 g + 32.0 g
D)2x mol $\to$ 2x mol + x mol
E)y(34.0 g) $\to$ y(18.0 g)+ y(32 g)

Answer 3

y(34.0 g) $\to$ y(18.0 g)+ y(32 g)

Question 4

Which of the following statements is NOT correct?

A)In the reaction,3 NO₂ + H₂O $\to$ 2 HNO₃ + xO,x must be a nitrogen atom.
B)If 100.00 grams of C₂H₄ react with 7.20 grams of H₂ to form C₂H₆,the final mass of the product must be 107.20 grams.
C)If 32 grams of oxygen gas react with hydrogen to form water,the mass of the product must be 32 grams.
D)When 2 moles of HNO₃ form from the complete reaction of N₂O₅ and H₂O,108 grams of N₂O₅ must have been used.
E)The mass of CO₂ produced by the reaction CH₄ + 2 O₂ $\to$ CO₂ + 2 H₂O equals the sum of the initial masses of CH₄ and O₂ minus the mass of water formed.

Question 5

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

A)177.3 g/mol
B)190.3 g/mol
C)208.2 g/mol
D)172.8 g/mol
E)202.8 g/mol

Question 6

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

A)0.705 mol
B)0.451 mol
C)0.331 mol
D)0.225 mol
E)0.676 mol

Question 7

Which relationship regarding the quantities of reactants and products associated with the following reaction is NOT correct? 6 H₂O( )+ P₄O₁₀ (s) $\to$ 4 H₃PO(aq)

A)6 molecules + 1 molecule $\to$ 4 molecules
B)18 mol + 6 mol $\to$ 12 mol
C)324 g + 852 g $\to$ 1176 g
D)6x mol + x mol $\to$ 4x mol
E)y(27 g)+ y(71 g) $\to$ y(98 g)

Question 8

Which of the following contains the largest number of atoms?

A)1 mol water
B)1 mol phosphorus trichloride
C)1 mol dinitrogen pentoxide
D)2 mol carbon monoxide
E)All of these contain the same number of atoms.

Question 9

A gallon of water has a mass of 3.79 kg.How many moles of water is this?

A)210 mol
B)0.210 mol
C)68.3 mol
D)68,300 mol
E)386 mol

Question 10

How many moles of ammonia are there in a 346 g sample of pure NH₃ (17.03 g/mol)?

A)0.0496 mol
B)20.3 mol
C)24.7 mol
D)5930 mol
E)3.46 mol

Question 11

Fuming sulfuric acid is obtained by the addition of SO₃ to concentrated H₂SO₄.The fumes result from the reaction of SO₃ gas with water vapor.What is the product when one molecule of SO₃ reacts with one molecule of water?

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

Question 12

Which statement about the following chemical reaction is NOT correct? 3 H₂(g)+ N₂(g) $\to$ 2 NH₃(g)

A)For every nitrogen molecule consumed,two molecules of ammonia are produced.
B)For every 6.06 grams of H₂ consumed,2 moles of NH₃ are produced.
C)If 34.0 grams of NH₃ are produced,28.0 grams of N₂ were consumed.
D)In order for 56 grams of N₂ to completely react,18 grams of H₂ would be required.
E)Three moles of nitrogen react with nine moles of hydrogen.

Question 13

What is the molar mass of sulfuric acid (H₂SO₄)?

A)49.0 g/mol
B)24.5 g/mol
C)101 g/mol
D)98.1 g/mol
E)97.0 g/mol

Question 14

Which statement about the following chemical reaction is NOT correct? 3 H₂(g)+ N₂(g) $\to$ 2 NH₃(g)

A)For every two moles of nitrogen consumed,three moles of ammonia are produced.
B)For every mole of nitrogen consumed,two moles of ammonia are produced.
C)For every three moles of hydrogen consumed,two moles of ammonia are produced.
D)For every two moles of ammonia produced,three moles of hydrogen are consumed.
E)Three moles of hydrogen will react with one mole of nitrogen to produce ammonia.

Question 15

Hydrogen peroxide decomposes to produce water and oxygen.Which relationship regarding the quantities of reactants and products associated with this reaction is NOT correct? 2 H₂O₂
$\to$ 2 H₂O + O₂(g)

A)68.0 g $\to$ 36.0 g + 32.0 g
B)34.0 g $\to$ 18.0 g + 16.0 g
C)90.4 g $\to$ 47.9 g + 42.6 g
D)2x g $\to$ 2x g + x g
E)y(34.0 g) $\to$ y(18.0 g)+ (y/2)(32 g)

Question 16

Which statement about the following chemical reaction is NOT correct? The molar masses of S₈,O₂,and SO₃ are 256,32.0,and 80.1 g/mol,respectively. S₈(s)+ 12 O₂(g) $\to$ 8 SO₃(g)

A)1 mol S₈ produces 8 mol SO₃.
B)256 g S₈ requires 12 mol O₂ in order to completely react.
C)In order to produce 8 mol SO₃,256 g S₈ and 192 g O₂ must react.
D)For every 6 mol O₂ consumed,4 mol SO₃ are produced.
E)If 641 g SO₃ are produced,a total mass of 641 g of S₈ and O₂ must react.

Question 17

A sample of water (H₂O)contains 1.81 $\times$ 10²⁴ molecules.How many moles of atoms are there in this sample?

A)1.00
B)2.00
C)3.00
D)6.00
E)9.00

Question 18

Which one of the following samples contains the fewest number of molecules? H is used as the symbol for hydrogen-1,and D is used as the symbol for hydrogen-2.

A)42 g of D₂O
B)2 moles of H₂O
C)2 moles of D₂O
D)36 g of H₂O
E)39 g of D₂O

Question 19

Fe₂O₃(s)and powdered aluminum can react with great output of heat to form molten iron and Al₂O₃.When this reaction equation is balanced,what are the stoichiometric coefficients in the following order: Fe₂O₃,Al,Fe,Al₂O₃?

A)1,1,1,1
B)2,2,2,2
C)1,2,2,1
D)2,1,1,2
E)1,1,2,2

Question 20

Hydrogen peroxide decomposes to produce water and oxygen.Which of the following statements is NOT correct? 2 H₂O₂( ) $\to$ 2 H₂O( )+ O₂(g)

A)The products of the reaction are liquids.
B)Water and oxygen are the products of the reaction.
C)The chemical formula of hydrogen peroxide is H₂O₂.
D)The reaction is balanced.
E)Two molecules of H₂O and one molecule of O₂ are produced when two molecules of H₂O₂ react.

Question 21

The average adult exhales about 1.0 kg of carbon dioxide each day.How much oxygen is needed in metabolizing glucose (C₆H₁₂O₆,180 g/mol)to make that much carbon dioxide?

A)180 g
B)1800 g
C)360 g
D)730 g
E)1500 g

Question 22

The combustion of butane (C₄H₁₀)forms carbon dioxide and water.What is the stoichiometric coefficient for oxygen in the balanced equation when 1 mol of butane undergoes combustion?

A)9
B)13
C)
D)
E)5

Question 23

During a fermentation process,sucrose (C₁₂H₂₂O₁₁)can react with water to form ethanol (C₂H₅OH)and carbon dioxide gas.What is the sum of the coefficients in the balanced chemical equation?

A)8
B)10
C)12
D)14
E)16

Question 24

Identify the set of stoichiometric coefficients that balance the reaction equation for the combustion of octane. C₈H₁₈
+ O₂(g) $\to$ CO₂(g)+ H₂O

A)1,25,8,9
B)1,17,8,9
C)2,34,16,18
D)2,25,16,18
E)None of the above coefficients balance the reaction equation

Question 25

In a one type of fuel cell,methanol (CH₃OH)enters on one side of the unit,and air enters on the other side.Both circulate past electrodes and chemically react to produce carbon dioxide and water along with electricity.Which chemical equation best represents the reaction that occurs?

A)CH₃OH $\to$ CO₂(g)+ 2 H₂O
B)2 CH₃OH + 3 O₂(g) $\to$ 2 CO₂(g)+ 4H₂O
C)CH₃OH $\to$ CH₂(g)+ H₂O
D)CH₃OH + N₂(g) $\to$ CH₃(g)+ NO(g)
E)CH₃OH + O₂(g) $\to$ CO₂(g)+ H₂O

Question 26

Sulfuric acid reacts with a vanadium oxide compound according to the following unbalanced reaction.What are the coefficients in the balanced chemical equation in the order in which it is written? H₂SO₄(aq)+ V₂O₃(s) $\to$ V₂(SO₄)₃(s)+ H₂O

A)3,1,1,3
B)3,2,3,3
C)3,1,1,6
D)3,2,2,6
E)6,3,3,12

Question 27

Extracting copper from sulfide ores can be performed by roasting the ore in oxygen,with a subsequent reaction of copper (I)oxide with carbon.Simplified chemical equations for these steps are shown below.Mathematically combine the two reactions to create an overall balanced equation.Eliminate like terms from your final equation and use the lowest whole-number coefficients possible.Select the statement regarding the overall balanced reaction that is NOT true. 2 Cu₂S(s)+ 3 O₂(g) $\to$ 2 Cu₂O(s)+ 2 SO₂(g)
Cu₂O(s)+ C(s) $\to$ 2 Cu(s)+ CO(g)

A)The balanced reaction requires three moles of oxygen gas.
B)Two moles of copper result when two moles of carbon react.
C)Cu₂O does not appear in the final balanced equation.
D)Two moles of CO gas are produced in the overall balanced equation.
E)There are three reactants and three products in the overall balanced equation.

Question 28

Air bags in cars inflate when an electrical spark activates sodium azide (NaN₃),so that it decomposes to sodium metal and nitrogen gas.In the balanced reaction equation,how many moles of N₂ gas are formed for each mole of NaN₃?

A)1
B)1.5
C)2
D)3
E)2.5

Question 29

Which statement,A-D,regarding photosynthesis is NOT correct? In the process of photosynthesis,__________

A)light energy is converted into carbon-based fuels.
B)oxygen is produced.
C)atmospheric carbon dioxide is consumed.
D)the sugar glucose is produced.
E)A-D are all correct.

Question 30

Chlorine atoms in the atmosphere can react with ozone.Mathematically combine the following two reactions to create an overall balanced equation with the lowest whole-number coefficients and select the statement that is NOT true.All chemical species in the reaction are gas-phase. Cl + O₃ $\to$ ClO + O₂
ClO + O $\to$ Cl + O₂

A)Chlorine atoms do not appear in the overall balanced reaction.
B)There is a net conversion of O₃ to O₂.
C)ClO does not appear in the overall balanced reaction.
D)Two chlorine atoms can cause the production of two oxygen atoms.
E)Oxygen atoms are produced by the overall reaction.

Question 31

Potassium perchlorate (KClO₃)oxidizes sucrose (C₁₂H₂₂O₁₁)according to the following unbalanced reaction.What are the coefficients in the balanced chemical equation in the order in which it is written? KClO₃(s)+ C₁₂H₂₂O₁₁(s) $\to$ KCl(s)+ CO₂(g)+ H₂O

A)4,1,4,12,11
B)4,1,4,12,22
C)2,1,2,12,11
D)8,1,8,12,11
E)8,2,8,12,11

Question 32

Diesel fuel for automobiles and trucks is a mixture of hydrocarbons that can be modeled by C₁₆H₃₄.Write the balanced reaction equation for the combustion of C₁₆H₃₄,and report the sum of the stoichiometric coefficients.

A)117
B)120
C)76
D)83
E)4

Question 33

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

Question 34

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?

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

Question 35

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?

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 36

What are the stoichiometric coefficients for oxygen and water,respectively,in the balanced chemical reaction equation representing the combustion of butane (C₄H₁₀)?

A)13,10
B)9,5
C)4,5
D) ,10
E)13,5

Question 37

Hydrazine (N₂H₄)can decompose to form nitrogen gas and ammonia gas.What is the sum of the coefficients in the balanced chemical equation?

A)4
B)5
C)6
D)7
E)8

Question 38

In a demonstration of the complete combustion of propane (C₃H₈)with oxygen (O₂),several balloons were prepared with various proportions by volume of propane and oxygen.The loudest explosion occurred for the balloon with the correct stoichiometric proportions of the gases.Which balloon had the loudest explosion?

A)1 portion propane to 1 portion oxygen
B)1 portion propane to 3 portions oxygen
C)1 portion propane to 4 portions oxygen
D)1 portion propane to 5 portions oxygen
E)2 portions propane to 3 portions oxygen

Question 39

In an aqueous solution under basic conditions,ozone (O₃)reacts with iodide (I^-)and water to form iodine (I₂),hydroxide (OH^-),and oxygen (O₂).What is the sum of the stoichiometric coefficients in the balanced reaction equation? O₃(g)+ I^-(aq)+ H₂O $\to$ I₂(aq)+ OH^-(aq)+ O₂(g)

A)6
B)8
C)10
D)12
E)14

Question 40

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?

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

Question 41

The space shuttle uses liquid hydrogen and liquid oxygen to produce thrust for liftoff in the following reaction: 2 H₂(l)+ O₂( ) $\to$ 2 H₂O(g)
If the liquid oxygen supply is set to provide 420 kg/s during a launch,what does the rate of liquid hydrogen supply need to be in kilograms per second?

A)840 kg/s
B)210 kg/s
C)106 kg/s
D)52.9 kg/s
E)63.4 kg/s

Question 42

The combustion of ethanol (CH₃CH₂OH,46.1 g/mol)results in the formation of water and carbon dioxide.How many grams of carbon dioxide are produced when 46.1 g of ethanol burns?

A)88.0 g
B)44.0 g
C)176 g
D)22.0 g
E)11.0 g

Question 43

The most abundant metal in Earth's crust is aluminum,found mostly in the form of clays.Bauxite ore,impure hydrated aluminum oxide,can be purified and refined to make the metal.After the first purification step,hydrated aluminum oxide (Al₂O₃ . xH₂O)is obtained.When 100.0 g of this solid was heated and the water driven off,65.36 g of Al₂O₃ remained.How many water molecules (x in the molecular formula)were there in the hydrate?

A)1
B)2
C)3
D)4
E)5

Question 44

As ammonium hydrogen carbonate (NH₄HCO₃,79.1 g/mol)is heated,it breaks down into three gases: ammonia,water,and carbon dioxide.For each 20.0 g of ammonium hydrogen carbonate heated (about 4 tsp),how many grams of carbon dioxide are produced?

A)15.9 g
B)6.67 g
C)5.06 g
D)11.1 g
E)20.0 g

Question 45

Suppose the combustion of fossil fuels adds about 8.0 $\times$ 10¹² kg of carbon to the atmosphere per year in the form of CO₂.How much oxygen gas is required to produce this amount of carbon dioxide?

A)about 2.1 $\times$ 10¹³ kg
B)about 5.8 $\times$ 10¹² kg
C)about 4.3 $\times$ 10¹² kg
D)about 1.1 $\times$ 10¹³ kg
E)about 4.8 $\times$ 10¹³ kg

Question 46

Which statement,A-D,regarding the carbon cycle is NOT correct?

A)Petroleum,coal,and other carbon sediments are produced.
B)Respiration produces atmospheric carbon dioxide.
C)Water is a reactant in photosynthesis.
D)Forest fires are part of the carbon cycle.
E)A-D are all correct.

Question 47

Hydrogen peroxide (H₂O₂)decomposes catalytically in the presence of metal ions and enzymes called peroxidases.If a 250 mL bottle of hydrogen peroxide solution containing 3.0% H₂O₂ (by mass)decomposes completely,how many liters of oxygen gas would it generate? Assume that 1 mol of gas occupies a volume of 22.4 L and that the density of the solution is 1.0 g/mL.The reaction is 2 H₂O₂(aq) $\to$ 2 H₂O( )+ O₂(g)

A)2.5 L
B)4.9 L
C)9.9 L
D)7.4 L
E)0.22 L

Question 48

Copper was the first metal to be produced from its ore because it is the easiest to smelt,that is,to refine by heating in the presence of carbon.The ore was likely malachite [Cu₂(OH)₂CO₃].What is the mass percent of copper in malachite?

A)28.7%
B)45.2%
C)57.5%
D)40.3%
E)74.6%

Question 49

The average adult exhales about 1.0 kg of carbon dioxide each day.How much glucose (C₆H₁₂O₆, 180 g/mol)is consumed to make that much carbon dioxide?

A)3.8 kg
B)4.1 kg
C)0.43 kg
D)0.68 kg
E)0.18 kg

Question 50

Assuming complete combustion,how many grams of butane (C₄H₁₀)would be required to consume 32.0 g O₂?

A)1.82 g
B)16.6 g
C)8.30 g
D)4.47g
E)8.94 g

Question 51

How many grams of CO₂ would result from the complete combustion of 4.00 mol butane (C₄H₁₀)?

A)24.2 g
B)176 g
C)704 g
D)96.9 g
E)1410 g

Question 52

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? 2 H₂O( ) $\to$ 2 H₂(g)+ O₂(g)

A)10.0 g
B)8.90 g
C)35.6 g
D)16.0 g
E)17.8 g

Question 53

Diesel fuel for automobiles and trucks is a mixture of hydrocarbons that can be modeled by C₁₆H₃₄.How many mL of C₁₆H₃₄ are needed to react with 1.00 mol O₂? The density of C₁₆H₃₄ is 0.773 g/mL and its molar mass is 226 g/mol.

A)9.23 mL
B)11.9 mL
C)0.561 mL
D)4.61 mL
E)0.140 mL

Question 54

Aluminum can form clusters that behave similarly to certain atoms. The “superatom,” Al₁₃, is thought to mimic chlorine. Suppose you create a process that generates KAl₁₃ (389.86 g/mol) and oxygen gas from aluminum oxide (101.96 g/mol) and potassium metal. How many grams of KAl₁₃ could be produced by the reaction of 102 grams of Al₂O₃? You will need to write a balanced chemical reaction.

A)390 g
B)97.5 g
C)60.0 g
D)15.00 g
E)141 g

Question 55

How much CO₂ is produced by a car driven 20,000 mi in one year? Assume the following:
• A car gets 20 mi/4.0 L of gasoline.
• Gasoline has the chemical formula of octane: C₈H₁₈.
• One liter of gasoline has a mass of 0.8 kg.
• Gasoline is completely burned to carbon dioxide and water.

A)1,500 kg
B)9,900 kg
C)15,000 kg
D)20,000 kg
E)4,900 kg

Question 56

If 20.0 kg CO₂ are produced from the combustion of butane (C₄H₁₀),calculate the mass of oxygen gas that was consumed.

A)23.6 kg
B)18.2 kg
C)11.8 kg
D)739 g
E)454 g

Question 57

Global carbon emissions in 2010 were estimated to be on the order of 9.0 $\times$ 10¹² metric tons carbon (1 metric ton = 1000 kg)in the form of CO₂.This is equivalent to __________ kg C.

A)about 2.5 $\times$ 10¹⁵ kg
B)about 7.5 $\times$ 10¹⁴ kg
C)about 2.0 $\times$ 10¹⁴ kg
D)about 1.7 $\times$ 10¹³ kg
E)about 1.2 $\times$ 10¹⁵ kg

Question 58

Copper(II)sulfate (CuSO₄)can be used to control algae growth.Aqueous CuSO₄ solutions that come in contact with the surface of galvanized (zinc-plated)steel pails undergo the following reaction: CuSO₄(aq)+ Zn(s) $\to$ Cu(s)+ ZnSO₄(aq)
How many grams of zinc would react with 454 g (1 lb)of CuSO₄ (160 g/mol)?

A)467 g
B)186 g
C)93 g
D)234 g
E)454 g

Question 59

Diesel fuel for automobiles and trucks is a mixture of hydrocarbons that can be modeled by C₁₆H₃₄.How many grams of O₂ are needed to react with 0.500 mol C₁₆H₃₄?

A)458 g
B)392 g
C)784 g
D)295g
E)196 g

Question 60

Arizona was the site of a 400,000-acre wildfire in June 2002.How much carbon dioxide was produced by this fire? Assume that the density of carbon on the acreage was 10 kg/m² and that 50% of the biomass burned (10,000 m² = 2.47 acre).

A)3 $\times$ 10¹⁰ kg
B)3 $\times$ 10⁶ kg
C)3 $\times$ 10³⁰ kg
D)3 $\times$ 10⁹ kg
E)3 $\times$ 10¹³ kg

Question 61

A compound containing bromine and fluorine used in the production of UF₆ is 58.37% Br by mass.What is the empirical formula for the compound?

A)BrF
B)Br₂F₃
C)BrF₃
D)BrF₅
E)Br₃F₂

Question 62

Ibuprofen is 75.69% C,8.80% H,and 15.51% O by mass.What is its empirical formula?

A)C₆H₉O
B)C₉H₉O₂
C)C₇H₁₈O₂
D)C₇H₉O₂
E)C₁₃H₁₈O₂

Question 63

A compound known to contain platinum,nitrogen,and hydrogen was analyzed and found to contain 74.1% Pt and 21.3% N; the remainder was hydrogen.What is the empirical formula for the compound?

A)Pt(NH₃)₄
B)Pt(NH₃)₃
C)Pt₂(NH₃)₂
D)Pt(NH₄)₂
E)Pt(NH₃)₆

Question 64

Which of the following does NOT share the same empirical formula as the others?

A)formaldehyde,CH₂O
B)acetic acid,CH₃COOH
C)lactic acid,CH₃CH(OH)COOH
D)butyric acid,CH₃CH₂CH₂COOH
E)glucose,C₆H₁₂O₆

Question 65

A 2.00 g sample of methamphetamine was found to contain 1.61 g C,0.203 g H,and 0.188 g N.What is its empirical formula?

A)C₁₀H₁₅N
B)C₄H₆N
C)C₄H₉N
D)C₁₃H₂₀N
E)C₈H₁₀N

Question 66

Alkanes share a general chemical formula of C_nH_2n+2.What is n of an alkane with a molar mass in the range of 125-130 g/mol?

A)10
B)9
C)8
D)11
E)12

Question 67

When are an empirical formula and a molecular formula the same?

A)Always
B)When the mass of the empirical formula unit is equal to the molecular mass
C)When the mass percentages of all of the elements in the two formulas are the same
D)Never
E)When the molecular mass is an integer multiple of formula unit mass

Question 68

A hydrocarbon is found to be 85.63% C by mass.What is its empirical formula?

A)CH
B)CH₂
C)CH₃
D)C₂H
E)CH₄

Question 69

Metallic copper can be obtained from the mineral chalcocite (Cu₂S).What is the mass percent of copper in chalcocite?

A)79.85%
B)66.46%
C)20.15%
D)33.54%
E)57.47%

Question 70

Paris green is a highly toxic emerald green compound with the formula Cu(C₂H₃O₂)₂ . 3Cu(AsO₂)₂.What is its percent by mass arsenic?

A)31.99%
B)14.78%
C)22.17%
D)7.389%
E)44.34%

Question 71

Hydroxylamine contains 42.41% N and 9.15% H by mass,with the remainder being oxygen.Determine its empirical formula.

A)N₁₄H₃O₁₆
B)N_4.6HO_5.3
C)N₅HO₅
D)N₃H₉O
E)NH₃O

Question 72

The empirical formula for buckminsterfullerene is C₁,and its molar mass is 720.6 g/mol.What is its molecular formula?

A)C₆₀
B)C₇₂
C)C₁₂
D)C₁
E)C₇₂₀

Question 73

Putrescine,a foul-smelling compound produced by decaying tissue,has the empirical formula C₂H₆N,and its molecular mass is found to be between 87 and 90 amu.How many empirical units are in the actual molecular formula?

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

Question 74

An iron ore,magnetite,contains only iron and oxygen.In refining 100.0 g of the ore,72.35 g of iron are obtained.What is the empirical formula of the ore?

A)Fe₂O₃
B)FeO₂
C)Fe₂O₅
D)Fe₃O₄
E)FeO

Question 75

A uranium oxide compound is found to be 88.15% U by mass.What is the empirical formula for the compound?

A)U₂O₃
B)UO₃
C)U₃O₄
D)UO₂
E)UO

Question 76

Analysis of two uranium fluoride compounds yields the following data: Compound I is 75.80% U by mass; compound II has an F-to-U mass ratio that is 1.5 times that of compound I.What is the empirical formula for compound II?

A)UF₄
B)UF₆
C)U₂F₃
D)UF₃
E)UF₂

Question 77

A gas that is produced when fruit ripens contains 85.62% C and 14.38% H by mass.The molecular mass was found to be twice the empirical formula unit molecular mass.What is the molecular formula of this gas?

A)CH₂
B)C₂H₂
C)C₂H₄
D)C₂H₆
E)C₄H₄

Question 78

Han purple,a synthetic inorganic pigment developed in China in ancient times,has the chemical formula BaCuSi₂O₆.What is its percent by mass silicon?

A)18.0%
B)15.9%
C)27.2%
D)38.9%
E)7.96%

Question 79

Caffeine has an elemental analysis of 49.48% C,5.190% H,16.47% O,and 28.85% N.It has a molar mass of 194.19 g/mol.What is the molecular formula of caffeine?

A)C₄H₅N₂O
B)C₈H₁₀N₄O₂
C)C₁₀H₁₄N₂O₂
D)C₆H₆NO₂
E)C₅H₇NO

Question 80

Phthalocyanine is a large molecule used in printing inks and dyes.Elemental analysis showed that it consists of 74.69% C,3.525% H,and 21.77 % N,and has a molar mass of 514.54 g/mol.What is its molecular formula?

A)C₁₆H₉N₄
B)C₃₀H₈N₁₀
C)C₃₂H₁₈N₈
D)C₃₂H₄N₉
E)C₁₆H₁₈N₄