The Mole and Stoichiometry REVIEW

True/False

Indicate whether the statement is true or false.

____1.The actual yield is always lower than the theoretical yield.

____2.The largest amount of starting material is always the excess reactant.

____3.Avogadro’s number refers to the number of particles in one gram of a substance.

____4.One mole of a substance has the same number of particles as one mole of any other substance, regardless of what substances are being compared.

____5.An element’s molar mass is equivalent to the atomic number of the element.

____6.If the atomic mass of a manganese atom is 54.94 amu, then its molar mass is 54.94 g/mol.

____7.Stoichiometry is the study of the relationship between the amount of reactants used and the amount of products made in a chemical reaction.

____8.In a balanced chemical equation, the total number of moles of all the reactants is equal to the total number of moles of all the products.

____9.The stoichiometric relationship between any two substances in a reaction depends on the mole ratio between those substances.

Multiple Choice

Identify the choice that best completes the statement or answers the question.

____10.Which conversion factor would best fit in the space labeled “B” in this diagram?

a. / 1/Avogadro’s number / c. / molar mass of substance
b. / Avogadro’s number / d. / 1/molar mass of substance

____11.Which element has a molar mass of 30.974 g/mol?

a. / Potassium / c. / Gallium
b. / Phosphorus / d. / Palladium

____12.Which is the correct molar mass for the compound FeSO4?

a. / 103.85 g/mol / c. / 415.4 g/mol
b. / 151.85 g/mol / d. / 247.85 g/mol

____13.What is the SI base unit used to measure the amount of a substance?

a. / Kelvin / c. / Meter
b. / Kilogram / d. / Mole

____14.Calculate the number of molecules in 4.0 mol H2O.

a. / 0.60  1023 molecules / c. / 2.4  10–23 molecules
b. / 2.4  1024 molecules / d. / 2.4  1023 molecules

____15.How many moles of Ag contain 4.49  1023 atoms Ag?

a. / 0.745  1024mol / c. / 0.745 mol
b. / 0.745  1023mol / d. / 27.0 mol

____16.Copper (Cu) is a transition element used in the making of coins. Calculate the mass in grams of 0.0420 moles of copper.

a. / 0.00697 g / c. / 2.67 g
b. / 0.252 g / d. / 6.61 g

____17.How many moles of calcium are in 425 g calcium (Ca)?

a. / 10.6 mol / c. / 171 mol
b. / 70.5 mol / d. / 255 mol

____18.What is the mass of 2.25 moles of sulfuric acid (H2SO4)?

a. / 50.0 g / c. / 112 g
b. / 98.0 g / d. / 220 g

____19.What is the mass in grams of 1.02  1024 atoms manganese (Mn)?

a. / 0.112  101 g / c. / 9.30  10–1 g
b. / 0.169  101 g / d. / 9.30  101 g

____20.Based on the mole ratios of the substances in a chemical reaction shown, which is the correct equation for the chemical reaction?

Substances / Mole ratio
A:B / 3:2
A:C / 3:1
B:C / 2:1
a. / / c. /
b. / / d. /

____21.Which is true of the reaction shown below?

a. / The mole ratio of this reaction is 6:5:6.
b. / Two molecules of Substance Y will be left over when this reaction goes to completion.
c. / Substance Y is the limiting reagent in this reaction.
d. / The addition of more molecules of Substance X will not affect the amount of Substance Z that can be made.

____22.Which conversion factor will correctly complete this setup for finding the number of moles of O2 required to completely react with 75.0 grams of Sb? The balanced chemical equation for the reaction is shown:

a. / 1 mole/31.998 g O2 / c. / 3 moles O2/4 moles Sb
b. / 4 moles Sb/3 moles O2 / d. / 31.998g O2 /1 mole

____23.How many moles of Cu are needed to react with 5.8 moles of AgNO3?

Cu + 2 AgNO3 Cu(NO3)2 + 2 Ag

a. / 2.9 moles / c. / 5.8 moles
b. / 3.8 moles / d. / 11.6 moles

____24.Hydrofluoric acid reacts with 31.3 g of silica to produce hexafluorosilicic acid. Determine the percent yield of H2SiF6 if the actual yield is 60.3 g.

a. / 0.818% / c. / 31.8%
b. / 12.2% / d. / 81.8%

The Mole and Stoichiometry REVIEW

Answer Section

TRUE/FALSE

1.ANS:TPTS:1DIF:EasyREF:Section 11.2

2.ANS:FPTS:1DIF:EasyREF:Section 11.3

3.ANS:FPTS:1DIF:Bloom's Level 1

NAT:B.2STA:ABC 11.2

4.ANS:TPTS:1DIF:Bloom's Level 2

NAT:B.2STA:ABC 11.2

5.ANS:FPTS:1DIF:Bloom's Level 1

NAT:B.1 | B.2STA:ABC 11.2

6.ANS:T

The molar mass of an element is numerically equal to its atomic mass.

PTS:1DIF:1REF:Page 313

OBJ:11.2.1 Relate the mass of an atom to the mass of a mole of atoms.

NAT:UCP.3 | B.1STA:ABC 11.2

TOP:Relate the mass of an atom to the mass of a mole of atoms.

KEY:Molar massMSC:1

NOT:The mass in grams of one mole of any pure substance is called its molar mass.

7.ANS:TPTS:1DIF:Bloom's Level 1

NAT:B.3STA:ABC 11.2

8.ANS:FPTS:1DIF:Bloom's Level 2

NAT:B.1 | B.2 | B.3STA:ABC 11.2

9.ANS:TPTS:1DIF:Bloom's Level 2

NAT:B.1 | B.2 | B.3STA:ABC 11.2

MULTIPLE CHOICE

10.ANS:CPTS:1DIF:Bloom's Level 2

NAT:UCP.2 | B.2STA:ABC 11.2

11.ANS:BPTS:1DIF:Bloom's Level 2

NAT:B.2STA:ABC 11.2

12.ANS:BPTS:1DIF:Bloom's Level 3

NAT:UCP.3 | B.2STA:ABC 11.2

13.ANS:D

The mole is an SI base unit used to measure the amount of a substance.

Feedback
A / Kelvin is the SI unit of thermodynamic temperature.
B / Kilogram is the SI unit of mass.
C / Meter is the SI unit of length.
D / Correct!

PTS:1DIF:1REF:Page 310

OBJ:11.1.1 Describe how a mole is used in chemistry.NAT:UCP.1 | UCP.3

STA:ABC 11.2TOP:Describe how a mole is used in chemistry.

KEY:MoleMSC:1

14.ANS:B

Feedback
A / Multiply the number of moles by the number of molecules.
B / Correct!
C / Multiply the number of moles with the correct value of Avogadro's number.
D / The position of the decimal value is incorrect.

PTS:1DIF:1REF:Page 311

OBJ:11.1.3 Convert moles to number of representative particles and number of representative particles to moles. NAT: UCP.3 STA: ABC 11.2

TOP:Convert moles to number of representative particles and number of representative particles to moles.

KEY:Converting moles to representative particlesMSC:3

15.ANS:C

Feedback
A / Multiply the number of atoms by the inverse of Avogadro's number.
B / After multiplying the number of atoms by the inverse of Avogadro's number, the power of the indices is nullified.
C / Correct!
D / Divide the number of atoms by Avogadro's number.

PTS:1DIF:1REF:Page 311

OBJ:11.1.3 Convert moles to number of representative particles and number of representative particles to moles. NAT: UCP.3 STA: ABC 11.2

TOP:Convert moles to number of representative particles and number of representative particles to moles.

KEY:Converting representative particles to molesMSC:3

16.ANS:C

Feedback
A / Instead of dividing the known number of moles of copper by Avogadro's number, multiply it with the molar mass of copper.
B / Instead of multiplying the known number of moles of copper by Avogadro's number, multiply it with the molar mass of copper.
C / Correct!
D / Multiply the known number of moles of copper by the molar mass of copper.

PTS:1DIF:1REF:Page 315

OBJ:11.2.2 Calculate the number of moles in a given mass of an element and the mass of a given number of moles of an element. NAT: UCP.3 | B.1 STA: ABC 11.2

TOP:Calculate the number of moles in a given mass of an element and the mass of a given number of moles of an element. KEY: Mole to mass conversion MSC: 3

17.ANS:A

Feedback
A / Correct!
B / Instead of dividing 425 g of calcium by Avogadro's number, divide it by its molar mass.
C / Multiply the known amount of calcium by the inverse of its molar mass.
D / Instead of multiplying 425 g of calcium by Avogadro's number, divide it by its molar mass.

PTS:1DIF:1REF:Page 316

OBJ:11.2.2 Calculate the number of moles in a given mass of an element and the mass of a given number of moles of an element. NAT: UCP.3 | B.1 STA: ABC 11.2

TOP:Calculate the number of moles in a given mass of an element and the mass of a given number of moles of an element. KEY: Mass to mole conversion MSC: 3

18.ANS:D

Step 1:

Step 2:

Feedback
A / The number of grams of sulfuric acid is 98.0 g.
B / Multiply the molar mass by 2.25 moles of sulfuric acid.
C / The atomic mass of oxygen is 16.
D / Correct!

PTS:1DIF:2REF:Page 323

OBJ:11.3.3 Calculate the number of moles of a compound from a given mass of the compound, and the mass of a compound from a given number of moles of the compound.

NAT:UCP.3STA:ABC 11.2

TOP:Calculate the number of moles of a compound from a given mass of the compound, and the mass of a compound from a given number of moles of the compound.

KEY:Converting moles of a compound to massMSC:3

19.ANS:D

Feedback
A / Divide the number of atoms by Avogadro's number and then multiply it by the molar mass of the element.
B / Multiply the calculated number of moles of the element by its molar mass.
C / Subtract 23 from the power of the element to obtain the correct power.
D / Correct!

PTS:1DIF:2REF:Page 318

OBJ:11.2.3 Calculate the number of moles of an element when given the number of atoms of the element.

NAT:UCP.3 | B.1STA:ABC 11.2

TOP:Calculate the number of moles of an element when given the number of atoms of the element.

KEY:Atoms to mass conversionMSC:3

20.ANS:DPTS:1DIF:Bloom's Level 2

NAT:UCP.2 | B.3STA:ABC 11.2

21.ANS:BPTS:1DIF:Bloom's Level 4

NAT:UCP.2 | B.3STA:ABC 11.2

22.ANS:CPTS:1DIF:Bloom's Level 4

NAT:UCP.2 | B.3STA:ABC 11.2

23.ANS:APTS:1DIF:Bloom's Level 3

NAT:UCP.3STA:ABC 11.2

24.ANS:D

Percent yield (actual yield/theoretical yield)  100

Feedback
A / Multiply the yield by 100 to calculate the percent yield.
B / Divide the actual yield by the theoretical yield.
C / The molar mass is incorrect.
D / Correct!

PTS:1DIF:3REF:Page 371

OBJ:12.4.2 Determine the percent yield for a chemical reaction.

NAT:UCP.3 | B.3STA:ABC 11.2TOP:Determine the percent yield for a chemical reaction.

KEY:Percent yieldMSC:3