,Portage Learning CHEM 103 General
Chemistry I Module 5 Lab Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
A student uses a eudiometer to collect gas via water displacement. If the water level
inside the eudiometer is exactly equal to the water level in the outside reservoir, how
does the pressure of the gas mixture inside compare to the room's atmospheric
pressure?
A) The internal pressure is exactly half of the atmospheric pressure.
B) The internal pressure is exactly equal to the atmospheric pressure.
C) The internal pressure is significantly higher than the atmospheric pressure.
D) The internal pressure is lower than the atmospheric pressure.
Correct Answer: B) The internal pressure is exactly equal to the atmospheric
pressure.
Rationale: When liquid levels inside and outside the tube are perfectly equalized, there
is no extra hydrostatic head pressure. This ensures that the total gas pressure inside
matches the ambient room barometric pressure.
Question 2
If the external water level is lower than the internal water level of an unadjusted
eudiometer tube, what corrective math adjustment is required if a student cannot
physically equalize the levels?
A) Add the height of the water column to the barometric pressure.
B) Subtract the hydrostatic pressure of the water column from the barometric pressure.
C) Multiply the barometric pressure by the water column height.
D) Ignore the height difference because water has no mass.
Correct Answer: B) Subtract the hydrostatic pressure of the water column from
the barometric pressure.
Rationale: When the internal liquid level is higher, the gas inside is under less pressure
than the atmosphere. The pressure of the gas mixture equals the barometric pressure
minus the pressure exerted by that raised column of water.
, Question 3
Which descriptive phase changes occur when dry ice (solid carbon dioxide) is allowed
to warm at normal room temperature and pressure during a gas demonstration?
A) Melting followed by boiling
B) Sublimation directly from solid to gas
C) Deposition from gas to solid
D) Condensation from liquid to gas
Correct Answer: B) Sublimation directly from solid to gas
Rationale: Dry ice undergoes sublimation because carbon dioxide cannot exist as a
liquid at standard atmospheric pressure. It transitions directly from a solid phase to a
gas phase.
Question 4
A student records a gas volume of 38.6 mL in a lab. What is this volume in standard
Liters (L) for use in the Ideal Gas Law equation?
A) 0.386 L
B) 0.0386 L
C) 3.86 L
D) 38,600 L
Correct Answer: B) 0.0386 L
Rationale: Converting milliliters to Liters requires dividing by 1,000 (\(\frac{38.6 \text{
mL}}{1,000 \text{ mL/L}} = 0.0386 \text{ L}\)). Using milliliters instead of Liters will cause
a large error in ideal gas law calculations.
Question 5
Which gas law explains why a flexible balloon shrinks in size when placed inside a
container of liquid nitrogen?
A) Boyle's Law
B) Charles's Law
C) Dalton's Law
D) Avogadro's Law
Correct Answer: B) Charles's Law
Chemistry I Module 5 Lab Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
A student uses a eudiometer to collect gas via water displacement. If the water level
inside the eudiometer is exactly equal to the water level in the outside reservoir, how
does the pressure of the gas mixture inside compare to the room's atmospheric
pressure?
A) The internal pressure is exactly half of the atmospheric pressure.
B) The internal pressure is exactly equal to the atmospheric pressure.
C) The internal pressure is significantly higher than the atmospheric pressure.
D) The internal pressure is lower than the atmospheric pressure.
Correct Answer: B) The internal pressure is exactly equal to the atmospheric
pressure.
Rationale: When liquid levels inside and outside the tube are perfectly equalized, there
is no extra hydrostatic head pressure. This ensures that the total gas pressure inside
matches the ambient room barometric pressure.
Question 2
If the external water level is lower than the internal water level of an unadjusted
eudiometer tube, what corrective math adjustment is required if a student cannot
physically equalize the levels?
A) Add the height of the water column to the barometric pressure.
B) Subtract the hydrostatic pressure of the water column from the barometric pressure.
C) Multiply the barometric pressure by the water column height.
D) Ignore the height difference because water has no mass.
Correct Answer: B) Subtract the hydrostatic pressure of the water column from
the barometric pressure.
Rationale: When the internal liquid level is higher, the gas inside is under less pressure
than the atmosphere. The pressure of the gas mixture equals the barometric pressure
minus the pressure exerted by that raised column of water.
, Question 3
Which descriptive phase changes occur when dry ice (solid carbon dioxide) is allowed
to warm at normal room temperature and pressure during a gas demonstration?
A) Melting followed by boiling
B) Sublimation directly from solid to gas
C) Deposition from gas to solid
D) Condensation from liquid to gas
Correct Answer: B) Sublimation directly from solid to gas
Rationale: Dry ice undergoes sublimation because carbon dioxide cannot exist as a
liquid at standard atmospheric pressure. It transitions directly from a solid phase to a
gas phase.
Question 4
A student records a gas volume of 38.6 mL in a lab. What is this volume in standard
Liters (L) for use in the Ideal Gas Law equation?
A) 0.386 L
B) 0.0386 L
C) 3.86 L
D) 38,600 L
Correct Answer: B) 0.0386 L
Rationale: Converting milliliters to Liters requires dividing by 1,000 (\(\frac{38.6 \text{
mL}}{1,000 \text{ mL/L}} = 0.0386 \text{ L}\)). Using milliliters instead of Liters will cause
a large error in ideal gas law calculations.
Question 5
Which gas law explains why a flexible balloon shrinks in size when placed inside a
container of liquid nitrogen?
A) Boyle's Law
B) Charles's Law
C) Dalton's Law
D) Avogadro's Law
Correct Answer: B) Charles's Law
