Deck 3: Stoichiometry

Question 1

What is the average mass, in grams, of one arsenic atom?

A)5.48 * 10^-23 g
B)33.0 g
C)74.9 g
D)1.24 * 10^-22 g
E)8.04 * 10²¹ g

Answer 1

1.24 * 10^-22 g

Question 2

What is the mass of 7.80 * 10¹⁸ carbon atoms?

A)1.30 * 10 ^-5 g
B)6.43 * 10³ g
C)7.80 * 10¹⁸ g
D)1.56 * 10 ^-4 g
E)12.01 g

Answer 2

1.56 * 10 ^-4 g

Question 3

Boron obtained from borax deposits in Death Valley consists of two isotopes. They are boron-10 and boron-11 with atomic masses of 10.013 amu and 11.009 amu, respectively. The atomic mass of boron is 10.81 amu (see periodic table). Which isotope of boron is more abundant, boron-10 or boron-11?

A)Cannot be determined from data given
B)Neither, their abundances are the same.
C)Boron-10
D)Boron-11

Answer 3

Boron-11

Question 4

The element oxygen consists of three naturally occuring isotopes: ¹⁶O, ¹⁷O, and ¹⁸O. The atomic mass of oxygen is 16.0 amu. What can be implied about the relative abundances of these isotopes?

A)More than 50% of all O atoms are ¹⁷O.
B)Almost all O atoms are ¹⁸O.
C)Almost all O atoms are ¹⁷O.
D)The isotopes all have the same abundance, i.e. 33.3%.
E)The abundances of ¹⁷O and ¹⁸O are very small.

Question 5

How many silicon atoms are there in 1.00 g of silicon?

A)1 atom
B)0.0356 atoms
C)2.57 * 10²³ atoms
D)2.14 * 10²² atoms
E)1.75 * 10²⁵ atoms

Question 6

An average atom of uranium (U)is approximately how many times heavier than an atom of potassium?

A)6.1 times
B)4.8 times
C)2.4 times
D)12.5 times
E)7.7 times

Question 7

Calculate the number of moles of xenon in 12.0 g of xenon.

A)1.00 mol
B)0.0457 mol
C)0.183 mol
D)7.62 * 10^-3 mol
E)0.0914 mol

Question 8

Which one of the following does not represent 1.00 mol of the indicated substance?

A)6.02 * 10²³ C atoms
B)26.0 g Fe
C)12.01 g C
D)65.4 g Zn
E)6.02 * 10²³ Fe atoms

Question 9

Determine the number of moles of aluminum in 96.7 g of Al.

A)0.279 mol
B)3.58 mol
C)7.43 mol
D)4.21 mol
E)6.02 * 10²³ mol

Question 10

If 0.274 moles of a substance weighs 62.5 g, what is the molar mass of the substance, in units of g/mol?

A)2.28 * 10² g/mol
B)1.71 * 10¹ g/mol
C)4.38 * 10 ^-3 g/mol
D)2.17 * 10² g/mol
E)none of these

Question 11

The mass of 1.21 *10²⁰ atoms of sulfur is

A)3.88 * 10²¹ g.
B)2.00 mg.
C)32.06 g.
D)6.44 mg.
E)2.00 * 10^-4 g.

Question 12

An atom of bromine has a mass about four times greater than that of an atom of neon. Which choice makes the correct comparison of the relative numbers of bromine and neon atoms in 1,000 g of each element?

A)The number of bromine and neon atoms is the same.
B)There are one thousand times as many bromine atoms as neon atoms.
C)There are one thousand times as many neon atoms as bromine atoms.
D)There are four times as many neon atoms as bromine atoms.
E)There are four times as many bromine atoms as neon atoms.

Question 13

An atom of helium has a mass about four times greater than that of an atom of hydrogen. Which choice makes the correct comparison of the relative numbers of helium and hydrogen atoms in equal masses of the two elements?

A)There are about four times as many helium atoms as hydrogen atoms.
B)There are about two times as many helium atoms as hydrogen atoms.
C)The number of helium and hydrogen atoms is the same.
D)There are about half as many helium atoms as hydrogen atoms.
E)There are about one-fourth as many helium atoms as hydrogen atoms.

Question 14

The mass of 1.63 * 10²¹ silicon atoms is

A)2.71 * 10^-23 g.
B)4.58 * 10²² g.
C)28.08 g.
D)1.04 * 10⁴ g.
E)7.60 * 10^-2 g.

Question 15

An atom of bromine has a mass about four times greater than that of an atom of neon. How many grams of neon will contain the same number of atoms as 1,000 g of bromine?

A)4 g Ne
B)250 g Ne
C)400 g Ne
D)1,000 g Ne
E)4,000 g Ne

Question 16

One mole of iron

A)is heavier than one mole of lead (Pb).
B)is 77.0 g of iron.
C)is 26.0 g of iron.
D)weighs the same as one mole of lead.
E)None of the above.

Question 17

One nanogram does not seem like a very large number. How many magnesium atoms are there in 1.00 ng of magnesium?

A)4.11 * 10^-11 atoms
B)2.48 * 10¹³ atoms
C)6.83 * 10^-35 atoms
D)6.02 * 10¹⁴ atoms
E)1.46 * 10³⁴ atoms

Question 18

There are two stable isotopes of chlorine: chlorine-35, with a mass of 34.968853 amu; and chlorine-37, with a mass of 36.965903. Given that the average atomic mass of a chlorine atom is 35.45 amu, which of the following statements is true?

A)Chlorine contains almost exclusively of Cl, with very little Cl.
B)Chlorine contains more Cl than Cl.
C)Chlorine contains roughly equal amounts of Cl and Cl.
D)Chlorine contains more Cl than Cl.
E)Chlorine contains almost exclusively of Cl, with very little Cl.

Question 19

What is the average mass, in grams, of one potassium atom?

A)5.14 * 10^-23 g
B)6.49 * 10^-23 g
C)6.02 * 10^-18 g
D)31.0 g
E)39.1 g

Question 20

What is the average mass, in grams, of one atom of iron?

A)6.02 * 10²³ g
B)1.66 * 10^-24 g
C)9.28 * 10^-23 g
D)55.85 g
E)55.85 * 10 ^-23 g

Question 21

A silver wire has a diameter of 0.500 mm. What length of this wire contains exactly 1.00 mol of silver? (density of Ag = 10.5 g/cm³)

A)52.3 m
B)222 m
C)13.1 m
D)2.01 m
E)890 m

Question 22

How many atoms are in 4.39 g of CO₂?

A)1.80 * 10²³ atoms
B)6.01 * 10²² atoms
C)1.16 * 10²⁶ atoms
D)6.04 * 10²⁴ atoms
E)1.81 * 10²⁵ atoms

Question 23

What is the molar mass of nicotine, C₁₀H₁₄N₂?

A)134 g/mol
B)148 g/mol
C)158 g/mol
D)210 g/mol
E)162 g/mol

Question 24

How many moles of NH₃ are there in 77.5 g of NH₃?

A)0.220 mol
B)4.55 mol
C)14.0 mol
D)1.31 * 10³ mol
E)None of the above.

Question 25

Calculate the molecular mass of potassium permanganate, KMnO₄.

A)52 amu
B)70 amu
C)110 amu
D)158 amu
E)176 amu

Question 26

Formaldehyde has the formula CH₂O. How many molecules are there in 0.11 g of formaldehyde?

A)6.1 * 10 ^-27
B)3.7 * 10 ^-3
C)4
D)2.2 * 10²¹
E)6.6 * 10²²

Question 27

A gold wire has a diameter of 1.00 mm. What length of this wire contains exactly 1.00 mol of gold? (density of Au = 17.0 g/cm³)

A)2630 m
B)3.69 m
C)251 m
D)14.8 m
E)62.7 m

Question 28

What is the mass of 0.0250 mol of P₂O₅?

A)35.5 g
B)5676 g
C)0.0250 g
D)1.51 * 10²² g
E)3.55 g

Question 29

Calculate the mass of 3.00 moles of CF₂Cl₂.

A)3.00 g
B)174 g
C)363 g
D)1.81 * 10²⁴ g
E)40.3 g

Question 30

How many moles of HCl are represented by 1.0 * 10¹⁹ HCl molecules?

A)1.7 * 10^-5 mol
B)1.5 * 10^-3 mol
C)1.0 * 10¹⁹ mol
D)36.5 mol
E)6.02 * 10⁴ mol

Question 31

How many molecules are there in 8.0 g of ozone, O₃?

A)3 molecules
B)3.6 * 10²⁴ molecules
C)1.0 * 10²³ molecules
D)3.0 * 10²³ molecules
E)6.0 * 10²³ molecules

Question 32

Calculate the molecular mass of menthol, C₁₀H₂₀O.

A)156 amu
B)140 amu
C)29 amu
D)146 amu
E)136 amu

Question 33

The molecular formula of aspirin is C₉H₈O₄. How many aspirin molecules are present in one 500-milligram tablet?

A)2.77 molecules
B)2.77 * 10^-3 molecules
C)1.67 * 10²⁴ molecules
D)1.67 * 10²¹ molecules
E)None of these is correct.

Question 34

A copper wire has a diameter of 2.00 mm. What length of this wire contains exactly 1.00 mol of copper? (density of Cu = 8.92 g/cm³)

A)0.178 m
B)0.567 m
C)180 m
D)45.1 m
E)2.27 m

Question 35

How many atoms are in 5.54 g of F₂?

A)6.02 * 10²³ atoms
B)0.146 atoms
C)0.292 atoms
D)8.78 * 10²² atoms
E)1.76 * 10²³ atoms

Question 36

How many atoms are in 0.0728 g of PCl₃?

A)1.28 * 10²¹ atoms
B)4.38 * 10²² atoms
C)4.39 * 10²¹ atoms
D)3.19 * 10²⁰ atoms
E)6.02 * 10²⁴ atoms

Question 37

Which of the following samples contains the greatest number of atoms?

A)100 g of Pb
B)2.0 mole of Ar
C)0.1 mole of Fe
D)5 g of He
E)20 million O₂ molecules

Question 38

What is the molar mass of acetaminophen, C₈H₉NO₂?

A)43 g/mol
B)76 g/mol
C)151 g/mol
D)162 g/mol
E)125 g/mol

Question 39

Calculate the number of moles of cesium in 50.0 g of cesium.

A)0.376 mol
B)0.357 mol
C)2.66 mol
D)2.80 mol
E)0.0200 mol

Question 40

How many moles of CF₄ are there in 171 g of CF₄?

A)0.51 mol
B)1.94 mol
C)4.07 mol
D)88.0 mol
E)171 mol

Question 41

How many sulfur atoms are present in 25.6 g of Al₂(S₂O₃)₃?

A)0.393
B)6
C)3.95 * 10²²
D)7.90 * 10²²
E)2.37 * 10²³

Question 42

Calculate the mass of 4.50 moles of chlorine gas, Cl₂.

A)6.34 * 10 ^-2 g
B)4.5 g
C)15.7 g
D)160 g
E)319 g

Question 43

How many carbon atoms are there in 10 lbs of sugar, C₁₂H₂₂O₁₁?

A)9.6 * 10²⁵ atoms
B)8.0 * 10²⁴ atoms
C)159 atoms
D)4.21 atoms
E)342 atoms

Question 44

What is the mass of 0.20 mole of C₂H₆O (ethanol)?

A)230 g
B)46 g
C)23 g
D)4.6 g
E)None of these.

Question 45

How many grams of sulfur are there in 6.0 g of Fe₂(SO₄)₃?

A)2.40 g
B)0.48 g
C)6.00 g
D)0.92 g
E)1.44 g

Question 46

The empirical formula of a compound of uranium and fluorine that is composed of 67.6% uranium and 32.4% fluorine is

A)U₂F.
B)U₃F₄.
C)UF₄.
D)UF₆.
E)UF₈.

Question 47

The mass of four moles of molecular bromine (Br₂)is

A)80 g.
B)320 g.
C)640 g.
D)140 g.
E)24 * 10²³ g.

Question 48

How many grams of sodium are there in 10. g of sodium sulfate, Na₂SO₄?

A)0.16 g
B)0.32 g
C)3.2 g
D)1.6 g
E)142 g

Question 49

How many grams of nitrogen are there in 7.5 g of Ca(NO₃)₂?

A)0.64 g
B)1.3 g
C)0.15 g
D)1.15 g
E)2.3 g

Question 50

A mass spectrometer works by ionizing atoms or molecules, and then accelerating them past oppositely charged plates. The mass is obtained by

A)measuring the force of impact on a detecting screen, and then calculating the mass using force = mass * acceleration.
B)suspending the ions in an applied electric field, and then calculating mass by setting the downward gravitational force equal to the upward electrostatic force.
C)measuring the magnitude of deflection as the ions pass through a magnetic field to obtain the charge-to-mass ratio, and then calculating the mass from that ratio.
D)measuring the time it takes for the ions to hit the detector at a known distance to calculate the acceleration, and then calculating mass from force = mass * acceleration.

Question 51

What is the mass of 8.25 * 10¹⁹ UF₆ molecules?

A)352 g
B)0.0482 g
C)1.37 * 10^-4 g
D)2.90 * 10²² g
E)8.25 * 10¹⁹ g

Question 52

How many moles of oxygen atoms are there in 10 moles of KClO₃?

A)3 mol
B)3.3 mol
C)10 mol
D)30 mol
E)6.02 * 10²⁴ mol

Question 53

How many O atoms are there in 51.4 g CaSO₄?

A)4
B)2.40 * 10²⁴
C)1.13
D)9.09 * 10²³
E)2.28 * 10²³

Question 54

How many fluorine atoms are there in 65 g of CF₄?

A)0.74 atoms
B)3.0 atoms
C)4.5 * 10²³ atoms
D)1.8 * 10²⁴ atoms
E)2.4 * 10²³ atoms

Question 55

How many sulfur atoms are there in 21.0 g of Al₂S₃?

A)8.42 * 10²² atoms
B)2.53 * 10²³ atoms
C)2.14 * 10²³ atoms
D)6.02 * 10²³ atoms
E)6.30 * 10²⁶ atoms

Question 56

What is the mass of 3.00 moles of ethanol, C₂H₆O?

A)4.99 * 10^-24 g
B)138 g
C)6.52 * 10^-2 g
D)50 g
E)1.81 * 10²⁴ g

Question 57

How many moles of Cl atoms are there in 65.2 g CHCl₃?

A)0.548 mol
B)1.09 mol
C)3.3 * 10²³ mol
D)1.64 mol
E)3.0 mol

Question 58

How many moles of O atoms are in 25.7 g of CaSO₄?

A)0.189 mol
B)0.755 mol
C)4.00 mol
D)1.14 * 10²³ mol
E)4.55 * 10²³ mol

Question 59

How many sodium atoms are there in 6.0 g of Na₃N?

A)3.6 * 10²⁴ atoms
B)4.6 * 10²² atoms
C)1.3 * 10²³ atoms
D)0.217 atoms
E)0.072 atoms

Question 60

The percent composition by mass of a compound is 76.0% C, 12.8% H, and 11.2% O. The molar mass of this compound is 284.5 g/mol. What is the molecular formula of the compound?

A)C₁₀H₆O
B)C₉H₁₈O
C)C₁₆H₂₈O₄
D)C₂₀H₁₂O₂
E)C₁₈H₃₆O₂

Question 61

Which one of the following chemical reactions is balanced?

A)HCl + KMnO₄ $\rarr$ Cl₂ + MnO₂ + H₂O + KCl
B)HCl + KMnO₄ $\rarr$ Cl₂ + MnO₂ + 2H₂O + KCl
C)2HCl + 2KMnO₄ $\rarr$ Cl₂ + MnO₂ + 2H₂O + 2KCl
D)6HCl + 2KMnO₄ $\rarr$ 2Cl₂ + 2MnO₂ + 4H₂O + 2KCl
E)8HCl + 2KMnO₄ $\rarr$ 3Cl₂ + 2MnO₂ + 4H₂O + 2KCl

Question 62

Balance the following equation using the smallest set of whole numbers, then add together the coefficients. Do not forget to count coefficients of one. The sum of the coefficients is __ SF₄ + __ H₂O $\rarr$ __ H₂SO₃ + __ HF

A)4.
B)6.
C)7.
D)9.
E)none of these.

Question 63

When 22.0 g NaCl and 21.0 g H₂SO₄ are mixed and react according to the equation below, which is the limiting reagent?
2NaCl + H₂SO₄ $\rarr$ Na₂SO₄ + 2HCl

A)NaCl
B)H₂SO₄
C)Na₂SO₄
D)HCl
E)No reagent is limiting.

Question 64

The percent composition by mass of an unknown chlorinated hydrocarbon was found to be 37.83% C, 6.35% H, and 55.83% Cl by mass. What is the empirical formula of this compound?

A)C₂H₄Cl
B)C₃H₇Cl
C)C₃H₆Cl₂
D)C₄H₉Cl
E)C₅H₁₁Cl

Question 65

When a chemical equation is balanced, it will have a set of whole number coefficients that cannot be reduced to smaller whole numbers. What is the coefficient for O₂ when the following combustion reaction of a hydrocarbon is balanced? ___ C₇H₁₄ + ___ O₂ $\rarr$ ___ CO₂ + ___ H₂O

A)42
B)21
C)11
D)10
E)none of these

Question 66

What is the coefficient preceding O₂ when the following combustion reaction of a fatty acid is properly balanced using the smallest set of whole numbers? __ C₁₈H₃₆O₂ + __ O₂ $\rarr$ __ CO₂ + __ H₂O

A)1
B)8
C)9
D)26
E)27

Question 67

Balance the following equation using the smallest set of whole numbers, then add together the coefficients. Do not forget to count coefficients of one. The sum of the coefficients is ___ Al + ___ H₂SO₄ $\rarr$ ___ Al₂(SO₄)₃ + ___ H₂

A)3.
B)5.
C)6.
D)9.
E)12.

Question 68

Vanadium(V)oxide reacts with calcium according to the chemical equation below. When 10.0 moles of V₂O₅ are mixed with 10.0 moles of Ca, which is the limiting reagent? V₂O₅(s)+ 5Ca(l) $\rarr$ 2V(l)+ 5CaO(s)

A)V₂O₅
B)Ca
C)V
D)CaO
E)No reagent is limiting.

Question 69

Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor: 4NH₃ + 5O₂ $\rarr$ 4NO + 6H₂O
When 40.0 g NH₃ and 50.0 g O₂ are allowed to react, which is the limiting reagent?

A)NH₃
B)O₂
C)NO
D)H₂O
E)No reagent is limiting.

Question 70

What is the coefficient of H₂O when the following equation is properly balanced with smallest set of whole numbers?
___ Al₄C₃ + ___ H₂O $\rarr$ ___ Al(OH)₃ + ___ CH₄

A)3
B)4
C)6
D)12
E)24

Question 71

When balanced with smallest set of whole numbers, the coefficient of O₂ in the following equation is __ C₂H₄ + __ O₂ $\rarr$ __ CO₂ + __ H₂O

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

Question 72

Balance the equation below using the smallest set of whole numbers. What is the coefficient of H₂O?
___ PCl₃(l)+ ___ H₂O(l) $\rarr$ ___ H₃PO₃(aq) + ___ HCl(aq)

A)1
B)2
C)3
D)5
E)none of these

Question 73

An organic thiol compound is 38.66% C, 9.73% H, and 51.61% S by mass. What is the empirical formula of this compound?

A)C₂H₆S
B)C₃H₈S
C)C₄H₁₀S
D)C₄H₁₂S
E)C₅H₁₄S

Question 74

Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor: 4NH₃ + 5O₂ $\rarr$ 4NO + 6H₂O
When 20.0 g NH₃ and 50.0 g O₂ are allowed to react, which is the limiting reagent?

A)NH₃
B)O₂
C)NO
D)H₂O
E)No reagent is limiting.

Question 75

A compound was discovered whose composition by mass is 85.6% C and 14.4% H. Which of the following could be the molecular formula of this compound?

A)CH₄
B)C₂H₄
C)C₃H₄
D)C₂H₆
E)C₃H₈

Question 76

What is the coefficient of H₂SO₄ when the following equation is properly balanced with the smallest set of whole numbers?
___ Ca₃(PO₄)₂ + ___ H₂SO₄ $\rarr$ ___ CaSO₄ + ___ H₃PO₄

A)3
B)8
C)10
D)11
E)none of these

Question 77

What is the coefficient of O₂ when the following equation is properly balanced with the smallest set of whole numbers?
___ CH₃OH + ___ O₂ $\rarr$ ___ CO₂ + ___ H₂O

A)1
B)2
C)3
D)7
E)none of these

Question 78

Balance the following equation using the smallest set of whole numbers, then add together the coefficients. Don't forget to count coefficients of one. The sum of the coefficients is ___ Cr + ___ H₂SO₄ $\rarr$ ___ Cr₂(SO₄)₃ + ___ H₂

A)4.
B)9.
C)11.
D)13.
E)15.

Question 79

What is the coefficient of H₂O when the following equation is properly balanced with the smallest set of whole numbers?
___ Na + ___ H₂O $\rarr$ ___ NaOH + ___ H₂

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

Question 80

Balance the following equation using the smallest set of whole numbers, then add together the coefficients. Do not forget to count coefficients of one. The sum of the coefficients is ___ CH₄ + ___ Cl₂ $\rarr$ ___ CCl₄ + ___ HCl

A)4.
B)6.
C)8.
D)10.
E)12.