Deck 3: Stoichiometry

Question 1

For which compound does 0.256 mole weigh 12.8 g?

A)C₂H₄O
B)CO₂
C)CH₃Cl
D)C₂H₆
E)none of these

Answer 1

CH₃Cl

Question 2

Naturally occurring element X exists in three isotopic forms: X-28 (27.977 amu,92.23% abundance),X-29 (28.976 amu,4.67% abundance),and X-30 (29.974 amu,3.10% abundance).Calculate the atomic weight of X.

A)28.09 amu
B)48.63 amu
C)27.16 amu
D)28.97 amu
E)86.93 amu

Answer 2

28.09 amu

Question 3

Calculate the molar mass of barium sulfite.

A)233.40 g/mol
B)201.40 g/mol
C)354.73 g/mol
D)514.87 g/mol
E)217.40 g/mol

Answer 3

217.40 g/mol

Question 4

The average mass of a carbon atom is 12.011.Assuming you were able to pick up only one carbon unit,the chances that you would randomly get one with a mass of 12.011 is

A)0%
B)0.011%
C)about 12%
D)12.011%
E)greater than 50%

Question 5

Naturally occurring element X exists in three isotopic forms: X-28 (27.977 amu,92.23% abundance),X-29 (28.976 amu,4.67% abundance),and X-30 (29.974 amu,3.10% abundance).What is the identity of element X?

A)Cu
B)Al
C)Ni
D)Si
E)Sr

Question 6

The atomic mass of rhenium is 186.2.Given that 37.1% of natural rhenium is rhenium-185,what is the other stable isotope?

A)
B)
C)
D)
E)

Question 7

A sample of ammonia has a mass of 43.5 g.How many molecules are in this sample?

A)2.55 molecules
B)2.62 $\times$ 10²⁵ molecules
C)2.36 $\times$ 10²³ molecules
D)1.54 $\times$ 10²⁴ molecules
E)8.63 $\times$ 10^-16 molecules

Question 8

Iron is biologically important in the transport of oxygen by red blood cells from the lungs to the various organs of the body.In the blood of an adult human,there are approximately 2.64 $\times$ 10¹³ red blood cells with a total of 2.90 g of iron.On the average,how many iron atoms are present in each red blood cell? (molar mass Fe = 55.85 g/mol)

A)8.44 $\times$ 10^-10
B)1.18 $\times$ 10⁹
C)3.13 $\times$ 10²²
D)2.64 $\times$ 10¹³
E)6.14 $\times$ 10^-2

Question 9

How many moles of hydrogen sulfide are contained in a 49.7-g sample of this gas?

A)0.686 mol
B)1.46 mol
C)83.8 mol
D)24.7 mol
E)2.92 mol

Question 10

A hypothetical element consists of two isotopes of masses 69.95 amu and 71.95 amu with abundances of 25.7% and 74.3%,respectively.What is the average atomic mass of this element?

A)70.95 amu
B)69.95 amu
C)70.5 amu
D)71.4 amu
E)71.95 amu

Question 11

What is the molar mass of ethanol (C₂H₅OH)?

A)45.06 g/mol
B)34.06 g/mol
C)46.07 g/mol
D)30.03 g/mol
E)105.03 g/mol

Question 12

Phosphoric acid can be prepared by reaction of sulfuric acid with "phosphate rock" according to the equation: Ca₃(PO₄)₂ + 3H₂SO₄ $\to$ 3CaSO₄ + 2H₃PO₄
How many oxygen atoms are there in 1.75 ng of Ca₃(PO₄)₂?

A)3.40 $\times$ 10¹²
B)1.36 $\times$ 10¹³
C)8.43 $\times$ 10¹⁵
D)2.72 $\times$ 10²²
E)2.72 $\times$ 10¹³

Question 13

Phosphoric acid can be prepared by reaction of sulfuric acid with "phosphate rock" according to the equation: Ca₃(PO₄)₂ + 3H₂SO₄ $\to$ 3CaSO₄ + 2H₃PO₄
What is the molar mass of Ca₃(PO₄)₂?

A)310.18 g/mol
B)87.05 g/mol
C)278.18 g/mol
D)215.21 g/mol
E)166.02 g/mol

Question 14

Roundup,an herbicide manufactured by Monsanto,has the formula C₃H₈NO₅P.How many moles of molecules are there in a 295.1-g sample of Roundup?

A)0.5729
B)2.137
C)1.745
D)16.39
E)none of these

Question 15

You have a sample of zinc (Zn)and a sample of aluminum (Al).You have an equal number of atoms in each sample.Which of the following statements concerning the masses of the samples is true?

A)The mass of the zinc sample is more than twice as great as the mass of the aluminum sample.
B)The mass of the zinc sample is more than the mass of the aluminum sample,but it is not twice as great.
C)The mass of the aluminum sample is more than twice as great as the mass of the zinc sample.
D)The mass of the aluminum sample is more than the mass of the zinc sample,but it is not twice as great.
E)The masses of each sample are equal.

Question 16

Phosphorus has the molecular formula P_4, and sulfur has the molecular formula S₈.How many grams of phosphorus contain the same number of molecules as 4.23 g of sulfur?

A)2.04 g
B)0.490 g
C)4.08 g
D)4.23 g
E)none of these

Question 17

A given sample of a xenon fluoride compound contains molecules of a single type XeF_n,where n is some whole number.Given that 8.06 $\times$ 10²⁰ molecules of XeF_n weigh 0.227 g,calculate n.

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

Question 18

Naturally occurring copper exists in two isotopic forms: ⁶³Cu and ⁶⁵Cu.The atomic mass of copper is 63.55 amu.What is the approximate natural abundance of ⁶³Cu?

A)63%
B)90%
C)70%
D)50%
E)30%

Question 19

What is the mass of 4 atom(s)of copper in grams?

A)254.2 g
B)2.37 $\times$ 10²¹ g
C)9.57 $\times$ 10^-24 g
D)6.022 $\times$ 10²³ g
E)4.22 $\times$ 10^-22 g

Question 20

Consider the element indium,atomic number 49,atomic mass 114.8 g.The nucleus of an atom of indium-112 contains

A)49 protons,63 neutrons,49 electrons
B)49 protons,49 neutrons
C)49 protons,49 alpha particles
D)49 protons,63 neutrons
E)49 protons,112 neutrons

Question 21

A substance contains 35.0 g nitrogen,5.05 g hydrogen,and 60.0 g of oxygen.How many grams of hydrogen are there in a 153-g sample of this substance?

A)7.72 g
B)767 g
C)15.4 g
D)5.05 g
E)30.3 g

Question 22

What is the mass of a 6.761-mol sample of sodium hydroxide?

A)40.00 g
B)270.4 g
C)162.3 g
D)5.916 g
E)0.1690 g

Question 23

The mineral vanadinite has the formula Pb₅(VO₄)₃Cl.What mass percent of chlorine does it contain?

A)7.51 %
B)3.08 %
C)9.91 %
D)2.50 %
E)1.13 %

Question 24

A substance,A₂B,has the composition by mass of 60% A and 40% B.What is the composition of AB₂ by mass?

A)40% A,60% B
B)50% A,50% B
C)27% A,73% B
D)33% A,67% B
E)none of these

Question 25

One molecule of a compound weighs 2.93 $\times$ 10^-22 g.The molar mass of this compound is:

A)2.06 g/mol
B)567 g/mol
C)168 g/mol
D)176 g/mol
E)none of these

Question 26

Chlorous acid,HClO₂,contains what percent hydrogen by mass?

A)1.92%
B)25.0%
C)23.4%
D)1.47%
E)5.18%

Question 27

NaHCO₃ is the active ingredient in baking soda.How many grams of oxygen are in 0.52 g of NaHCO₃?

A)0.099 g
B)0.019 g
C)6.19 $\times$ 10³ g
D)0.033 g
E)0.30 g

Question 28

The molar mass of an insecticide,dibromoethane,is 187.9 g/mol.Its molecular formula is C₂H₄Br₂.What percent by mass of bromine does dibromoethane contain?

A)42.52%
B)2.14%
C)85.05%
D)12.78%
E)6.39%

Question 29

Each molecule of testosterone contains 19 atoms of carbon (plus other atoms).The mass percent of carbon in testosterone is 79.12%.What is the molar mass of testosterone?

A)576.8 g/mol
B)180.5 g/mol
C)228.2 g/mol
D)240.1 g/mol
E)288.4 g/mol

Question 30

A compound is composed of element X and hydrogen.Analysis shows the compound to be 80% X by mass,with three times as many hydrogen atoms as X atoms per molecule.Which element is element X?

A)He
B)C
C)F
D)S
E)none of these

Question 31

A mixture of KCl and KNO₃ is 44.20% potassium by mass.The percentage of KCl in the mixture is closest to

A)40%
B)50%
C)60%
D)70%
E)80%

Question 32

Hydrocortisone valerate is an ingredient in hydrocortisone cream,prescribed for skin problems.Its molecular formula is C₂₆H₃₈O₆.What is the percent by mass of carbon in hydrocortisone valerate?

A)69.9%
B)43.6%
C)54.2%
D)76.9%
E)60.1%

Question 33

The molar mass of the compound formed by potassium and selenium is

A)157.2 g/mol
B)197.0 g/mol
C)118.1 g/mol
D)276.0 g/mol
E)196.3 g/mol

Question 34

A substance contains 23.0 g sodium,27.0 g aluminum,and 114 g fluorine.How many grams of sodium are there in a 102-g sample of the substance?

A)4.43 g
B)23.0 g
C)14.3 g
D)102 g
E)none of these

Question 35

Which compound contains the highest percent by mass of hydrogen?

A)HCl
B)H₂O
C)H₂SO₄
D)H₂S
E)HF

Question 36

Which of the following compounds has the same percent composition by mass as styrene,C₈H₈?

A)acetylene,C₂H₂
B)benzene,C₆H₆
C)cyclobutadiene,C₄H₄
D)" $\alpha$ -ethyl naphthalene",C₁₂H₁₂
E)all of these

Question 37

How many atoms of hydrogen are present in 7.63 g of ammonia?

A)2.70 $\times$ 10²³
B)1.52 $\times$ 10²⁴
C)1.38 $\times$ 10²⁵
D)8.09 $\times$ 10²³
E)1.12 $\times$ 10²⁰

Question 38

What is the molar mass of cryolite (Na₃AlF₆)?

A)209.9 g/mol
B)185.3 g/mol
C)210.0 g/mol
D)104.2 g/mol
E)68.97 g/mol

Question 39

How many grams of potassium are in 27.8 g of K₂CrO₇?

A)4.49 g
B)1.422 g
C)8.98 g
D)78.2 g
E)55.6 g

Question 40

An oxide of iron has the formula Fe₃O₄.What mass percent of iron does it contain?

A)0.72%
B)28%
C)30%
D)70%
E)72%

Question 41

A 2.80-g sample of an oxide of bromine is converted to 4.698 g of AgBr.Calculate the empirical formula of the oxide.(molar mass for AgBr = 187.78 g/mol)

A)BrO₃
B)BrO₂
C)BrO
D)Br₂O
E)none of these

Question 42

Vitamin C contains the elements C,H,and O.It is known to contain 40.9% C and 4.58% H by mass.The molar mass of vitamin C has been found to be about 180 g/mol.The molecular formula for vitamin C is:

A)C₂H₃O₂
B)C₃H₄O₃
C)C₄H₆O₄
D)C₆H₈O₆
E)C₁₄H₁₈

Question 43

A hydrocarbon (a compound consisting solely of carbon and hydrogen)is found to be 85.6% carbon by mass.What is the empirical formula for this compound?

A)CH
B)CH₂
C)C₂H
D)C₃H
E)CH₄

Question 44

The empirical formula of styrene is CH;its molar mass is 104.1 g/mol.What is the molecular formula of styrene?

A)C₂H₄
B)C₈H₈
C)C₁₀H₁₂
D)C₆H₆
E)none of these

Question 45

You take an aspirin tablet (a compound consisting solely of carbon,hydrogen,and oxygen)with a mass of 1.00 g,burn it in air,and collect 2.20 g of carbon dioxide and 0.400 g water.The molar mass of aspirin is between 170 and 190 g/mol.The molecular formula of aspirin is

A)C₆H₈O₅
B)C₉H₈O₄
C)C₈H₁₀O₅
D)C₁₀H₆O₄
E)none of these

Question 46

Ammonium chromate, (NH₄)₂CrO₄,contains what percent nitrogen by mass?

A)36.8%
B)9.2%
C)18.4%
D)11.9%
E)none of these

Question 47

Which of the following equations is not balanced?

A)4Al + 3O₂ $\to$ 2Al₂O₃
B)C₂H₆ + O₂ $\to$ 2CO₂ + 3H₂O
C)2KClO₃ $\to$ 2KCl + O₂
D)4P₄ + 5S₈ $\to$ 4P₄S₁₀
E)P₄ + 5O₂ $\to$ P₄O₁₀

Question 48

What is the coefficient for water when the following equation is balanced? As(OH)₃(s)+ H₂SO₄(aq) $\to$ As₂(SO₄)₃(aq)+ H₂O(l)

A)1
B)2
C)4
D)6
E)12

Question 49

The empirical formula of a group of compounds is CHCl.Lindane,a powerful insecticide,is a member of this group.The molar mass of lindane is 290.8 g/mol.How many atoms of carbon does a molecule of lindane contain?

A)2
B)3
C)4
D)6
E)8

Question 50

Adipic acid contains 49.32% C,43.84% O,and 6.85% H by mass.What is the empirical formula?

A)C₃H₅O₂
B)C₃H₃O₄
C)C₂HO₃
D)C₂H₅O₄
E)C₃HO₃

Question 51

You heat 3.854 g of a mixture of Fe₃O₄ and FeO to form 4.148 g Fe₂O₃.The mass percent of FeO originally in the mixture was:

A)92.9%
B)55.8%
C)44.2%
D)38.5%
E)none of these

Question 52

In balancing an equation,we change the __________ to make the number of atoms on each side of the equation balance.

A)formulas of compounds in the reactants
B)coefficients of compounds
C)formulas of compounds in the products
D)subscripts of compounds
E)none of these

Question 53

Balanced chemical equations imply which of the following?

A)Numbers of molecules are conserved in chemical change.
B)Numbers of atoms are conserved in chemical change.
C)Volume is conserved in chemical change.
D)A and B
E)B and C

Question 54

A chloride of rhenium contains 63.6% rhenium.What is the formula of this compound?

A)ReCl
B)ReCl₃
C)ReCl₅
D)ReCl₇
E)Re₂Cl₃

Question 55

A 0.4987-g sample of a compound known to contain only carbon,hydrogen,and oxygen was burned in oxygen to yield 0.9267 g of CO₂ and 0.1897 g of H₂O.What is the empirical formula of the compound?

A)CHO
B)C₂H₂O
C)C₃H₃O₂
D)C₆H₃O₂
E)C₃H₆O₂

Question 56

A compound composed of sulfur and fluorine is found to contain 62.79% by mass of sulfur.If the molar mass of the compound is 102.13 g/mol,what is its molecular formula?

A)S₃F
B)S₂F₄
C)SF
D)S₂F
E)S₂F₂

Question 57

The molecular formula always represents the total number of atoms of each element present in a compound.

Question 58

Suppose you are given the percent by mass of the elements in a compound and you wish to determine the empirical formula.Which of the following is true?

A)You must convert percent by mass to relative numbers of atoms.
B)You must assume exactly 100.0 g of the compound.
C)You must divide all of the percent by mass numbers by the smallest percent by mass.
D)You cannot solve for the empirical formula without the molar mass.
E)At least two of the above (A-D)are true.

Question 59

How many of the following are true concerning balanced chemical equations?
I.The number of molecules is conserved.
II.The coefficients for the reactants tell you how much of each reactant you are given.
III.Atoms are neither created nor destroyed.
IV.The coefficients indicate the mass ratios of the substances used.
V.The sum of the coefficients on the reactant side equals the sum of the coefficients on
The product side.

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

Question 60

Oxides of copper include CuO and Cu₂O.You heat 1.51 g of one of these copper oxides in the absence of air and obtain 1.21 g of Cu.
True or false: You must have had CuO.

Question 61

What is the coefficient for oxygen when the following equation is balanced? NH₃(g)+ O₂(g) $\to$ NO₂(g)+ H₂O(g)

A)3
B)6
C)7
D)12
E)14

Question 62

When the equation C₆H₁₄ + O₂ $\to$ CO₂ + H₂O is balanced with the smallest set of integers,the sum of the coefficients is

A)4
B)47
C)15
D)27
E)34

Question 63

Indium reacts with chlorine to form InCl₃.In the balanced equation for this reaction,the coefficient of the indium trichloride is

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

Question 64

wPCl₅ + xH₂O $\to$ yPOCl₃ + zHCl The above equation is properly balanced when:

A)w = 1,x = 2,y = 2,z = 4
B)w = 2,x = 2,y = 2,z = 2
C)w = 2,x = 2,y = 2,z = 1
D)w = 1,x = 1,y = 1,z = 2
E)none of these

Question 65

To balance a chemical equation,the coefficients must not be changed.

Question 66

What is the sum of the coefficients of the following equation when it is balanced using smallest whole numbers? NaNH₂ + NaNO₃ $\to$ NaN₃ +NaOH + NH₃

A)5
B)6
C)7
D)8
E)9

Question 67

The correct coefficients to balance the following reaction are,in order: I₂O₅ + H₂S $\to$ I₂ + SO₂ + H₂O

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

Question 68

You heat 3.869 g of a mixture of Fe₃O₄ and FeO to form 4.141 g Fe₂O₃.The mass of oxygen reacted is

A)0.272 g
B)0.476 g
C)1.242 g
D)1.000 g
E)none of these

Question 69

The Claus reactions,shown below,are used to generate elemental sulfur from hydrogen sulfide. 2H₂S + 3O₂ $\to$ 2SO₂ + 2H₂O
SO₂ + 2H₂S $\to$ 3S + 2H₂O
How much sulfur (in grams)is produced from 21.5 grams of O₂?

A)97.0 g
B)14.4 g
C)21.5 g
D)43.1 g
E)none of these

Question 70

Which of the following equations correctly describes the combustion of CH₄ and O₂ to produce water (H₂O)and carbon dioxide (CO₂)?

A)CH₄ + O₂ $\to$ CO₂ + H₂O
B)CH₄ + O₂ $\to$ CO₂ + 2H₂O
C)CH₄ + 2O₂ $\to$ CO₂ + 2H₂O
D)CH₄ + 3O₂ $\to$ 2CO₂ + H₂O
E)2CH₄ + 3O₂ $\to$ 2CO₂ + 2H₂O

Question 71

When the following equation is balanced,what is the sum of the coefficients? Al₂(SO₄)₃ + Ca(OH)₂ $\to$ Al(OH)₃ + CaSO₄

A)4
B)9
C)8
D)7
E)10

Question 72

Consider a specific chemical reaction represented by the equation aA + bB $\to$ cC + dD.In this equation the letters A,B,C,and D represent chemicals,and the letters a,b,c,and d represent coefficients in the balanced equation.

-How many possible values are there for the quantity "c"?

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

Question 73

Consider a specific chemical reaction represented by the equation aA + bB $\to$ cC + dD.In this equation the letters A,B,C,and D represent chemicals,and the letters a,b,c,and d represent coefficients in the balanced equation.

-How many possible values are there for the quantity "c/d"?

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

Question 74

In the balanced equation for the reaction: xP₄O₆(s)+ yH₂O(l) $\to$ zH₃PO₃(aq)
If x equals 2,the coefficient z equals:

A)2
B)4
C)6
D)10
E)none of these

Question 75

When balancing a chemical equation,it is generally best to start with the least complicated molecules.

Question 76

How many of the following statements are true concerning chemical equations? I.Coefficients can be fractions.
II.Subscripts can be fractions.
III.Coefficients represent the relative masses of the reactants and/or products.
IV.Changing the subscripts to balance an equation can only be done once.
V.Atoms are conserved when balancing chemical equations.

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

Question 77

A reaction occurs between sodium carbonate and hydrochloric acid producing sodium chloride,carbon dioxide,and water.The correct set of coefficients,respectively,for the balanced reaction is:

A)3 6 6 3 4
B)8 6 5 10 5
C)5 10 10 5 5
D)1 2 2 1 1
E)none of these

Question 78

Potassium forms an oxide containing 1 oxygen atom for every 2 atoms of potassium.What is the coefficient of oxygen in the balanced equation for the reaction of potassium with oxygen to form this oxide?

A)0
B)1
C)2
D)3
E)4

Question 79

Determine the coefficient for O₂ when the following equation is balanced in standard form (smallest whole numbers). C₈H₁₈(g)+ O₂(g) $\to$ CO₂(g)+ H₂O(g)

A)8
B)17
C)18
D)25
E)16

Question 80

Give (in order)the correct coefficients to balance the following reaction: H₂SnCl₆ + H₂S $\to$ SnS₂ + HCl

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