CHEM-120 UNIT 7 LAB PRACTICUM 2026/2027 | Graded A |
100% Correct Solutions | Pass Guaranteed - A+ Graded
SECTION 1: Laboratory Safety & Equipment (Q1-Q8)
Q1: A student is preparing to perform an acid-base titration in the CHEM-120 lab. Which
personal protective equipment (PPE) is required at minimum before beginning the
experiment?
A. Safety goggles and closed-toe shoes only
B. Safety goggles, gloves, and a lab coat [CORRECT]
C. Face shield and respirator only
D. Safety goggles and disposable apron only
Correct Answer: B
Rationale: Standard CHEM-120 lab protocols require safety goggles, nitrile gloves, and a
lab coat for all wet chemistry procedures. Face shields and respirators are reserved for
specific high-hazard operations, while aprons alone do not provide adequate arm and
torso protection.
Q2: In the CHEM-120 laboratory, where should aqueous waste containing dilute acids be
disposed?
A. In the regular trash bin
B. Down the sink with copious water
C. In the designated hazardous liquid waste container [CORRECT]
D. In the broken glass container
Correct Answer: C
Rationale: Even dilute acid waste must be collected in designated hazardous waste
containers for proper neutralization and disposal by certified handlers. Disposing acids
down the sink violates EPA regulations and can damage plumbing, while trash and glass
containers are inappropriate for liquid chemicals.
Q3: A student needs to deliver 25.00 mL of a standard NaOH solution to an Erlenmeyer
flask for a titration. Which piece of glassware should be selected?
,A. 50 mL beaker
B. 25 mL volumetric pipette [CORRECT]
C. 25 mL graduated cylinder
D. 50 mL burette
Correct Answer: B
Rationale: A 25 mL volumetric pipette is calibrated to deliver (TD) exactly 25.00 mL with
high precision, making it ideal for transferring fixed volumes in titration setups. Beakers
and graduated cylinders lack the necessary precision, while a burette is designed for
variable-volume delivery, not fixed-volume transfer.
Q4: During a titration, a student accidentally splashes a small amount of 0.1 M HCl on
their forearm. What is the correct immediate response?
A. Apply sodium bicarbonate powder directly to the skin
B. Wipe with a paper towel and continue working
C. Flush the affected area with water for 15 minutes and notify the instructor [CORRECT]
D. Neutralize with concentrated NaOH solution
Correct Answer: C
Rationale: The universal first aid for chemical skin exposure is immediate and thorough
water flushing for at least 15 minutes to dilute and remove the chemical. Applying
powders or concentrated bases can cause additional thermal or chemical burns, and
continuing work without treatment risks delayed injury.
Q5: A student obtains a reading of 12.45 mL from a burette, but a lab partner notices
the student read the meniscus from above rather than at eye level. What type of error
does this introduce, and how does it affect the calculated molarity of the analyte?
A. Random error; the calculated molarity may be higher or lower
B. Systematic error; the calculated molarity will be consistently too high [CORRECT]
C. Systematic error; the calculated molarity will be consistently too low
D. Gross error; the experiment must be completely restarted
Correct Answer: B
Rationale: Reading a burette from above eye level causes parallax, consistently yielding
a lower volume reading than actual. Since the calculated molarity depends on volume
delivered in the denominator (M = moles/V), an underestimated volume produces a
systematically overestimated molarity.
, Q6: Which of the following best describes the proper procedure for storing concentrated
nitric acid in the CHEM-120 stockroom?
A. In a flammable storage cabinet with organic solvents
B. In a dedicated corrosive cabinet below eye level, away from bases and organics
[CORRECT]
C. On the lab bench in a clear glass bottle for easy access
D. In a refrigerator shared with organic reagents
Correct Answer: B
Rationale: Concentrated nitric acid is a strong oxidizing acid and corrosive that must be
segregated from bases (to prevent neutralization hazards) and organic materials (to
prevent oxidation fires). Corrosive cabinets below eye level minimize splash risk to the
face during retrieval.
Q7: If a small fire starts on a hot plate in the lab, which extinguishing method is most
appropriate?
A. Spray with water from the sink
B. Smother with a fire blanket or use a Class B/C fire extinguisher [CORRECT]
C. Blow on the flames to extinguish them
D. Pour acetone on the fire to cool it
Correct Answer: B
Rationale: Electrical and small chemical fires are best smothered with a fire blanket or
extinguished with a Class B/C dry chemical extinguisher. Water conducts electricity and
can spread flammable liquid fires, while blowing or adding organic solvents feeds the
fire with oxygen or fuel.
Q8: A student weighs a hygroscopic solid on an analytical balance using weighing paper
instead of a weighing boat or covered container. What is the most likely consequence?
A. The mass reading will be systematically high due to static charge
B. The sample will absorb moisture from the air, causing an inaccurate high mass
reading [CORRECT]
C. The balance will display an error message and refuse to measure
D. The sample will evaporate, causing a low mass reading
Correct Answer: B
Rationale: Hygroscopic solids rapidly absorb atmospheric moisture. Weighing paper
exposes the sample to air, leading to mass gain from water absorption and artificially
100% Correct Solutions | Pass Guaranteed - A+ Graded
SECTION 1: Laboratory Safety & Equipment (Q1-Q8)
Q1: A student is preparing to perform an acid-base titration in the CHEM-120 lab. Which
personal protective equipment (PPE) is required at minimum before beginning the
experiment?
A. Safety goggles and closed-toe shoes only
B. Safety goggles, gloves, and a lab coat [CORRECT]
C. Face shield and respirator only
D. Safety goggles and disposable apron only
Correct Answer: B
Rationale: Standard CHEM-120 lab protocols require safety goggles, nitrile gloves, and a
lab coat for all wet chemistry procedures. Face shields and respirators are reserved for
specific high-hazard operations, while aprons alone do not provide adequate arm and
torso protection.
Q2: In the CHEM-120 laboratory, where should aqueous waste containing dilute acids be
disposed?
A. In the regular trash bin
B. Down the sink with copious water
C. In the designated hazardous liquid waste container [CORRECT]
D. In the broken glass container
Correct Answer: C
Rationale: Even dilute acid waste must be collected in designated hazardous waste
containers for proper neutralization and disposal by certified handlers. Disposing acids
down the sink violates EPA regulations and can damage plumbing, while trash and glass
containers are inappropriate for liquid chemicals.
Q3: A student needs to deliver 25.00 mL of a standard NaOH solution to an Erlenmeyer
flask for a titration. Which piece of glassware should be selected?
,A. 50 mL beaker
B. 25 mL volumetric pipette [CORRECT]
C. 25 mL graduated cylinder
D. 50 mL burette
Correct Answer: B
Rationale: A 25 mL volumetric pipette is calibrated to deliver (TD) exactly 25.00 mL with
high precision, making it ideal for transferring fixed volumes in titration setups. Beakers
and graduated cylinders lack the necessary precision, while a burette is designed for
variable-volume delivery, not fixed-volume transfer.
Q4: During a titration, a student accidentally splashes a small amount of 0.1 M HCl on
their forearm. What is the correct immediate response?
A. Apply sodium bicarbonate powder directly to the skin
B. Wipe with a paper towel and continue working
C. Flush the affected area with water for 15 minutes and notify the instructor [CORRECT]
D. Neutralize with concentrated NaOH solution
Correct Answer: C
Rationale: The universal first aid for chemical skin exposure is immediate and thorough
water flushing for at least 15 minutes to dilute and remove the chemical. Applying
powders or concentrated bases can cause additional thermal or chemical burns, and
continuing work without treatment risks delayed injury.
Q5: A student obtains a reading of 12.45 mL from a burette, but a lab partner notices
the student read the meniscus from above rather than at eye level. What type of error
does this introduce, and how does it affect the calculated molarity of the analyte?
A. Random error; the calculated molarity may be higher or lower
B. Systematic error; the calculated molarity will be consistently too high [CORRECT]
C. Systematic error; the calculated molarity will be consistently too low
D. Gross error; the experiment must be completely restarted
Correct Answer: B
Rationale: Reading a burette from above eye level causes parallax, consistently yielding
a lower volume reading than actual. Since the calculated molarity depends on volume
delivered in the denominator (M = moles/V), an underestimated volume produces a
systematically overestimated molarity.
, Q6: Which of the following best describes the proper procedure for storing concentrated
nitric acid in the CHEM-120 stockroom?
A. In a flammable storage cabinet with organic solvents
B. In a dedicated corrosive cabinet below eye level, away from bases and organics
[CORRECT]
C. On the lab bench in a clear glass bottle for easy access
D. In a refrigerator shared with organic reagents
Correct Answer: B
Rationale: Concentrated nitric acid is a strong oxidizing acid and corrosive that must be
segregated from bases (to prevent neutralization hazards) and organic materials (to
prevent oxidation fires). Corrosive cabinets below eye level minimize splash risk to the
face during retrieval.
Q7: If a small fire starts on a hot plate in the lab, which extinguishing method is most
appropriate?
A. Spray with water from the sink
B. Smother with a fire blanket or use a Class B/C fire extinguisher [CORRECT]
C. Blow on the flames to extinguish them
D. Pour acetone on the fire to cool it
Correct Answer: B
Rationale: Electrical and small chemical fires are best smothered with a fire blanket or
extinguished with a Class B/C dry chemical extinguisher. Water conducts electricity and
can spread flammable liquid fires, while blowing or adding organic solvents feeds the
fire with oxygen or fuel.
Q8: A student weighs a hygroscopic solid on an analytical balance using weighing paper
instead of a weighing boat or covered container. What is the most likely consequence?
A. The mass reading will be systematically high due to static charge
B. The sample will absorb moisture from the air, causing an inaccurate high mass
reading [CORRECT]
C. The balance will display an error message and refuse to measure
D. The sample will evaporate, causing a low mass reading
Correct Answer: B
Rationale: Hygroscopic solids rapidly absorb atmospheric moisture. Weighing paper
exposes the sample to air, leading to mass gain from water absorption and artificially
