CHEM 1311
Test 4
1311 General Chemistry I Summer 2025
The School of Integrative Biological and Chemical Sciences
Name:
Date:
Instructions: Answer each question carefully. Multiple-choice questions have one correct answer unless
otherwise stated.
I.
Multiple Choice (Single Answer) – 20 Questions
1. What is the definition of boiling point?
A. The temperature at which vapor pressure equals atmospheric pressure
B. The temperature at which a substance freeze
C. The amount of energy required to melt a solid
D. The pressure exerted by a vapor at equilibrium
2. Which variable remains constant during a phase change?
A. Temperature
B. Pressure
C. Volume
D. Energy
3. Which law relates pressure and volume at constant temperature?
A. Boyle’s Law
B. Charles’ Law
C. Avogadro’s Law
D. Gay-Lussac’s Law
4. What does the triple point in a phase diagram represent?
A. All three phases exist in equilibrium
B. The substance becomes a supercritical fluid
C. The critical temperature is reached
D. The melting point equals boiling point
5. What happens to kinetic energy during heating?
A. It increases
B. It decreases
C. It remains constant
D. It becomes potential energy
6. What is the unit of the ideal gas constant R when using atm?
A. 0.0821 L·atm/mol·K
B. 8.31 J/mol·K
C. 1.00 atm·L/mol·K
D. 22.4 L/mol
7. Which state of matter is most compressible?
A. Gas
B. Liquid
C. Solid
D. Plasma
8. Which type of compound has a higher melting point?
A. Ionic
B. Covalent
C. Nonpolar
D. Molecular
9. What law applies when inflating a balloon at constant temperature?
A. Boyle’s Law
B. Gay-Lussac’s Law
C. Charles’ Law
D. Avogadro’s Law
10. According to Charles’ Law, what happens to volume when temperature increases?
A. Increases
B. Decreases
C. Remains constant
D. Doubles
11. What does a flat section in a heating curve indicate?
A. A phase change
B. A temperature increase
C. A decrease in pressure
D. No heat is added
12. What is the molar mass of H₂SO₄?
A. 98.09 g/mol
B. 36.46 g/mol
C. 63.01 g/mol
D. 18.02 g/mol
13. What is normality?
A. Equivalents per liter
B. Moles per liter
C. Grams per mole
D. Molecules per liter
14. How many molecules are in 2 moles of H₂O?
A. 1.20 x 10²⁴
B. 6.02 x 10²³
C. 3.01 x 10²³
D. 2.00 x 10²³
15. What defines standard conditions for gases?
A. 1 atm and 0°C
B. 1 atm and 25°C
C. 0 atm and 273 K
D. 100 kPa and 298 K
16. What is Avogadro’s number?
A. 6.022 x 10²³
B. 1.008 x 10²⁴
C. 3.14 x 10²⁰
D. 4.44 x 10²²
17. What type of energy changes during melting?
A. Potential energy
B. Kinetic energy
C. Thermal energy
D. Chemical energy
18. Which substance has the higher vapor pressure at room temperature?
A. Ethanol
B. Water
C. Salt
D. Ice
19. Which property decreases when temperature drops?
A. Kinetic energy
B. Mass
C. Volume
D. Molarity
20. What is the critical point?
A. Above which no liquid can exist
B. Where freezing and melting occur
C. Point of max density
D. Beginning of sublimation
II. Calculation Exercises (Show full process) — 5 questions
1. A hydrated sample of calcium chloride (CaCl₂·2H₂O) weighs 7.35 g. How many moles of
anhydrous CaCl₂ are present?
Full process
A) 0.0985 mol
B) 0.0500 mol
C) 0.0768 mol
D) 0.127 mol
2. Determine the number of neon atoms in a 3.50 L container filled with neon gas at STP.
Full Process
(STP: 22.4 L/mol, Avogadro’s number = 6.022 × 10²³ atoms/mol)
A) 9.41 × 10²² atoms
B) 5.43 × 10²³ atoms
C) 3.22 × 10²¹ atoms
D) 1.25 × 10²² atoms
3. A solution is prepared by dissolving 2.5 mol of NaCl in enough water to make 750 mL of
solution. What is the molarity?
Full process
A) 1.25 M
B) 3.33 M
C) 0.75 M
D) 2.90 M
4. Calculate the number of molecules in 14.0 g of nitrogen dioxide (NO₂).
Full Process
A) 3.06 × 10²³ molecules
B) 9.13 × 10²² molecules
C) 1.12 × 10²⁴ molecules
D) 6.02 × 10²³ molecules
5. How many grams of H₂O are produced when 6.00 g of H₂ react with excess O₂?
Reaction: H₂ + O₂ → H₂O
Full process
A) 53.7 g
B) 18.0 g
C) 21.6 g
D) 6.00 g
III. Multiple Selection (More than one correct answer) — 15 Questions
1. Which conditions increase the pressure of a gas?
A. Increase temperature
B. Decrease volume
C. Decrease number of moles
D. Expand the container
2. What happens at the critical point?
A. Sublimation occurs
B. Liquid and gas phases become indistinguishable
C. Freezing occurs
D. The substance reaches its highest temperature for liquid-vapor equilibrium
3. Which factors affect vapor pressure?
A. Temperature
B. Intermolecular forces
C. Volume
D. Molarity
4. Which characteristics correspond to ideal gases?
A. No intermolecular forces
B. Particles occupy no volume
C. High density
D. Strong attractions between particles
5. What happens during evaporation?
A. Molecules escape from the surface of a liquid
B. Energy is absorbed
C. The temperature decreases automatically
D. Condensation increases
6. Which formulas relate to molar mass?
A. M = g/mol
B. M = dRT/P
C. M = PV/nRT
D. M = mol × g
7. Which substances undergo sublimation?
A. Dry ice (CO₂)
B. Iodine crystals
C. Water
D. Sodium chloride
8. Which elements affect normality (N)?
A. Number of equivalents
B. Volume of solution
C. Temperature
D. Color of the solute
9. What does a phase diagram equilibrium line represent?
A. Conditions where two phases coexist
B. The melting point only
C. The boiling point only
D. Balance between pressure and temperature for phase change
10. Which compounds have ionic bonds?
A. NaCl
B. CaF₂
C. H₂O
D. CH₄
11. Which conditions indicate real gas behavior?
A. High pressure
B. Low temperature
C. High volume
D. Ideal conditions
12. What happens to volume if the temperature is doubled (at constant pressure)?
A. Volume also doubles
B. Volume halves
C. Pressure decreases
D. Volume remains constant
13. Which substances have weaker intermolecular forces?
A. Helium (He)
B. Water (H₂O)
C. Methane (CH₄)
D. Ammonia (NH₃)
14. Which factors affect solubility?
A. Temperature
B. Nature of solute and solvent
C. Pressure (for gases)
D. Color of the solution
15. What type of energy is associated with temperature?
A. Kinetic energy
B. Potential energy
C. Chemical energy
D. Nuclear energy
IV. Reading Comprehension — 5 Questions
The Ideal Gas Model
The ideal gas law is a simplified model that assumes gas particles do not attract or repel each other and
that they occupy no volume. It works well under conditions of low pressure and high temperature but fails
to accurately predict behavior when gases are compressed or cooled.
1. Which of the following is an assumption of the ideal gas model?
A. Gas particles have significant volume
B. Gas particles are strongly attracted to one another
C. Gas particles experience no intermolecular forces
D. The model applies at any temperature
Real Gas Behavior
At high pressure, gas particles are forced close together, making the volume of the particles and the
intermolecular forces between them significant. As a result, real gases deviate from ideal behavior, and
corrections like the van der Waals equation may be used to improve accuracy.
2. What causes real gases to deviate from ideal behavior?
A. Extreme temperatures
B. High particle speed
C. Particle collisions with container walls
D. Significant volume and intermolecular forces
Sublimation
Sublimation is a phase change in which a substance transitions directly from solid to gas without
becoming liquid. Substances like dry ice (solid CO₂) and iodine can sublimate under standard atmospheric
conditions due to their high vapor pressure.
3. Which substance is most likely to undergo sublimation at room temperature?
A. Ice
B. Sodium chloride
C. Iodine
D. Ethanol
Vapor Pressure
Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid phase. It depends on
temperature and the strength of intermolecular forces. Higher temperatures and weaker intermolecular
forces lead to higher vapor pressure.
4. Which factor increases the vapor pressure of a liquid?
A. Increasing intermolecular forces
B. Lowering the temperature
C. Increasing temperature
D. Increasing liquid density
Applications of Gas Laws
The ideal gas law and other related equations (Boyle’s, Charles’s, and Avogadro’s laws) are used to solve
problems involving pressure, volume, temperature, and amount of gas. These laws are applied in fields
such as medicine, meteorology, and engineering.
5. Which of the following variables is not part of the ideal gas law?
A. Volume
B. Pressure
C. Temperature
D. Density
V. Creative, Analytical, or Application-Based Questions — 5 Questions (You can draw or
write)
1. Analyze a heating curve for water and describe what is happening during each segment of the
graph.
2. Design a simple experiment to demonstrate Boyle’s Law using basic materials.
3. How would you explain the concept of molarity to an 8th-grade student in simple terms?
4. Explain why the heat of vaporization is greater than the heat of fusion for most substances.
5. Describe how the behavior of gases changes as you climb a mountain (consider pressure and
temperature).
Good Luck! Congratulations for your hard work!
Section
Description
# of Questions
I
Multiple Choice
(1 correct)
Calculation with
full process
Multiple
Selection
(multiple
correct)
Reading
Comprehension
Creative /
Analytical /
Application
TOTAL
20
Value per
Question
1.5%
5
4.0%
20%
15
1.67%
25%
5
2.0%
10%
5
3.0%
15%
II
III
IV
V
50
Section Total
30%
100%