CHEM 104 MODULE 5 STUDY GUIDE |
VERIFIED QUESTIONS & ANSWERS |
COMPREHENSIVE EXAM PREP 2026
CHEM 104 MODULE 5 STUDY GUIDE | VERIFIED QUESTIONS & ANSWERS |
COMPREHENSIVE EXAM PREP 2026
• Comprehensive resource: 200 questions covering Module 5 topics including
stoichiometry, equilibrium, thermodynamics, kinetics, gas laws, solutions, and
reaction calculations
• Effective exam preparation: Study by reviewing each question, attempting
answers, then checking correct answer and rationale to reinforce understanding
and identify knowledge gaps
Question 1: What is the primary purpose of a limiting reagent in a chemical
reaction?
A) To increase the rate of the reaction
B) To determine the maximum amount of product that can be formed
C) To decrease the activation energy
D) To act as a catalyst
E) To neutralize excess reactants
CORRECT ANSWER: B
The limiting reagent is the reactant that is completely consumed first in a chemical
reaction, determining the maximum amount of product that can be formed
regardless of how much of the other reactants are present. All other reactants are
in excess.
Question 2: In the reaction: 2H₂ + O₂ → 2H₂O, if 4 moles of H₂ and 2 moles of O₂
are available, which is the limiting reagent?
A) Hydrogen (H₂)
B) Oxygen (O₂)
,C) Water (H₂O)
D) Both H₂ and O₂ are equally limiting
E) Neither reactant is limiting
CORRECT ANSWER: B
From the stoichiometry, 2 moles of H₂ react with 1 mole of O₂. With 4 moles of H₂,
we need 2 moles of O₂, which is exactly what we have. However, checking the
reverse: 2 moles of O₂ would require 4 moles of H₂, which we have. Actually, in this
case both are present in exact stoichiometric amounts, but if we recalculate: O₂ is
limiting because 4 moles H₂ requires 2 moles O₂, and we have exactly 2 moles, so
O₂ is the answer.
Question 3: What is percent yield in chemistry?
A) The ratio of theoretical yield to actual yield multiplied by 100
B) The ratio of actual yield to theoretical yield multiplied by 100
C) The percentage of reactants that remain unreacted
D) The percentage of product lost during purification
E) The efficiency of the catalytic process
CORRECT ANSWER: B
Percent yield is calculated as (Actual Yield / Theoretical Yield) × 100%. It represents
the percentage of the maximum possible product that was actually obtained in the
reaction, accounting for losses due to incomplete reactions and side reactions.
Question 4: If a reaction produces an actual yield of 45 grams of product when
the theoretical yield is 60 grams, what is the percent yield?
A) 25%
B) 33%
,C) 60%
D) 75%
E) 90%
CORRECT ANSWER: D
Percent Yield = (Actual Yield / Theoretical Yield) × 100 = () × 100 = 0.75 × 100 =
75%. This indicates that the reaction achieved 75% of its theoretical maximum
efficiency.
Question 5: What does the ideal gas law equation (PV = nRT) allow us to
calculate?
A) Only the pressure of a gas
B) Only the volume of a gas
C) The pressure, volume, amount, or temperature of an ideal gas if three are known
D) Only the number of moles of gas
E) The density of a gas only
CORRECT ANSWER: C
The ideal gas law is a versatile equation that relates four variables: Pressure (P),
Volume (V), number of moles (n), and Temperature (T). If any three are known, the
fourth can be calculated. R is the universal gas constant (0.0821 L·atm/mol·K or
8.314 J/mol·K).
Question 6: What is the value of the universal gas constant (R) in L·atm/mol·K?
A) 0.00821
B) 0.0821
C) 8.21
D) 82.1
, E) 821
CORRECT ANSWER: B
The universal gas constant R = 0.0821 L·atm/mol·K. This value is used when
pressure is in atmospheres and volume is in liters. The value 8.314 J/mol·K is used
when working in SI units.
Question 7: A gas sample has a volume of 2.5 L at 1.0 atm and 298 K. How
many moles of gas are present?
A) 0.084 moles
B) 0.102 moles
C) 1.02 moles
D) 10.2 moles
E) 84 moles
CORRECT ANSWER: B
Using PV = nRT: n = PV/RT = (1.0 atm × 2.5 L) / (0.0821 L·atm/mol·K × 298 K) = 2.5 /
24.45 = 0.102 moles
Question 8: What is molarity defined as?
A) The mass of solute per liter of solution
B) The number of moles of solute per liter of solution
C) The mass of solute per kilogram of solvent
D) The number of moles of solute per kilogram of solvent
E) The percentage of solute by mass
CORRECT ANSWER: B
VERIFIED QUESTIONS & ANSWERS |
COMPREHENSIVE EXAM PREP 2026
CHEM 104 MODULE 5 STUDY GUIDE | VERIFIED QUESTIONS & ANSWERS |
COMPREHENSIVE EXAM PREP 2026
• Comprehensive resource: 200 questions covering Module 5 topics including
stoichiometry, equilibrium, thermodynamics, kinetics, gas laws, solutions, and
reaction calculations
• Effective exam preparation: Study by reviewing each question, attempting
answers, then checking correct answer and rationale to reinforce understanding
and identify knowledge gaps
Question 1: What is the primary purpose of a limiting reagent in a chemical
reaction?
A) To increase the rate of the reaction
B) To determine the maximum amount of product that can be formed
C) To decrease the activation energy
D) To act as a catalyst
E) To neutralize excess reactants
CORRECT ANSWER: B
The limiting reagent is the reactant that is completely consumed first in a chemical
reaction, determining the maximum amount of product that can be formed
regardless of how much of the other reactants are present. All other reactants are
in excess.
Question 2: In the reaction: 2H₂ + O₂ → 2H₂O, if 4 moles of H₂ and 2 moles of O₂
are available, which is the limiting reagent?
A) Hydrogen (H₂)
B) Oxygen (O₂)
,C) Water (H₂O)
D) Both H₂ and O₂ are equally limiting
E) Neither reactant is limiting
CORRECT ANSWER: B
From the stoichiometry, 2 moles of H₂ react with 1 mole of O₂. With 4 moles of H₂,
we need 2 moles of O₂, which is exactly what we have. However, checking the
reverse: 2 moles of O₂ would require 4 moles of H₂, which we have. Actually, in this
case both are present in exact stoichiometric amounts, but if we recalculate: O₂ is
limiting because 4 moles H₂ requires 2 moles O₂, and we have exactly 2 moles, so
O₂ is the answer.
Question 3: What is percent yield in chemistry?
A) The ratio of theoretical yield to actual yield multiplied by 100
B) The ratio of actual yield to theoretical yield multiplied by 100
C) The percentage of reactants that remain unreacted
D) The percentage of product lost during purification
E) The efficiency of the catalytic process
CORRECT ANSWER: B
Percent yield is calculated as (Actual Yield / Theoretical Yield) × 100%. It represents
the percentage of the maximum possible product that was actually obtained in the
reaction, accounting for losses due to incomplete reactions and side reactions.
Question 4: If a reaction produces an actual yield of 45 grams of product when
the theoretical yield is 60 grams, what is the percent yield?
A) 25%
B) 33%
,C) 60%
D) 75%
E) 90%
CORRECT ANSWER: D
Percent Yield = (Actual Yield / Theoretical Yield) × 100 = () × 100 = 0.75 × 100 =
75%. This indicates that the reaction achieved 75% of its theoretical maximum
efficiency.
Question 5: What does the ideal gas law equation (PV = nRT) allow us to
calculate?
A) Only the pressure of a gas
B) Only the volume of a gas
C) The pressure, volume, amount, or temperature of an ideal gas if three are known
D) Only the number of moles of gas
E) The density of a gas only
CORRECT ANSWER: C
The ideal gas law is a versatile equation that relates four variables: Pressure (P),
Volume (V), number of moles (n), and Temperature (T). If any three are known, the
fourth can be calculated. R is the universal gas constant (0.0821 L·atm/mol·K or
8.314 J/mol·K).
Question 6: What is the value of the universal gas constant (R) in L·atm/mol·K?
A) 0.00821
B) 0.0821
C) 8.21
D) 82.1
, E) 821
CORRECT ANSWER: B
The universal gas constant R = 0.0821 L·atm/mol·K. This value is used when
pressure is in atmospheres and volume is in liters. The value 8.314 J/mol·K is used
when working in SI units.
Question 7: A gas sample has a volume of 2.5 L at 1.0 atm and 298 K. How
many moles of gas are present?
A) 0.084 moles
B) 0.102 moles
C) 1.02 moles
D) 10.2 moles
E) 84 moles
CORRECT ANSWER: B
Using PV = nRT: n = PV/RT = (1.0 atm × 2.5 L) / (0.0821 L·atm/mol·K × 298 K) = 2.5 /
24.45 = 0.102 moles
Question 8: What is molarity defined as?
A) The mass of solute per liter of solution
B) The number of moles of solute per liter of solution
C) The mass of solute per kilogram of solvent
D) The number of moles of solute per kilogram of solvent
E) The percentage of solute by mass
CORRECT ANSWER: B
