CHEM 120 LAB PRACTICUM | QUESTIONS AND ANSWERS |
VERIFIED ANSWERS PLUS RATIONALES | EXAM ALREADY
GRADED A+ | LATEST EXAM
1. Which piece of lab equipment is used to accurately measure 25.0 mL of liquid?
A. Beaker
B. Erlenmeyer flask
C. Volumetric pipette
D. Graduated cylinder
Answer: C. Volumetric pipette
Rationale: A volumetric pipette is calibrated to deliver precise volumes, making it ideal for
accurate measurements.
2. What is the purpose of a meniscus in liquid measurement?
A. To mix solutions
B. To indicate the volume accurately
C. To increase reaction rate
D. To prevent spillage
Answer: B. To indicate the volume accurately
Rationale: The meniscus forms at the liquid’s surface; reading the bottom of the meniscus
ensures accurate volume measurement.
3. Which chemical is commonly used to standardize a sodium hydroxide solution?
A. Hydrochloric acid
B. Potassium hydrogen phthalate (KHP)
C. Acetic acid
D. Sodium chloride
Answer: B. Potassium hydrogen phthalate (KHP)
Rationale: KHP is a primary standard that reacts stoichiometrically with NaOH, allowing
accurate titration.
4. During titration, the endpoint is reached when:
A. All the analyte is evaporated
B. The indicator changes color
C. The solution boils
D. The pH is 7
Answer: B. The indicator changes color
Rationale: The indicator signals the completion of the reaction by changing color at the
equivalence point.
5. Which technique is used to separate a solid from a liquid in a mixture?
A. Filtration
B. Distillation
,C. Chromatography
D. Titration
Answer: A. Filtration
Rationale: Filtration separates solids from liquids by passing the mixture through filter paper.
6. What safety equipment must be worn when handling strong acids?
A. Gloves and goggles
B. Apron only
C. Open-toed shoes
D. Face mask only
Answer: A. Gloves and goggles
Rationale: Gloves protect skin and goggles protect eyes from corrosive chemicals.
7. If a solution is diluted, what happens to its concentration?
A. Increases
B. Decreases
C. Remains the same
D. Doubles
Answer: B. Decreases
Rationale: Dilution adds solvent, lowering the solute concentration without changing the amount
of solute.
8. The density of a liquid can be calculated using:
A. Mass/volume
B. Volume × concentration
C. Mass × temperature
D. Pressure/volume
Answer: A. Mass/volume
Rationale: Density is defined as the mass per unit volume of a substance.
9. What is the function of a fume hood?
A. To heat solutions
B. To protect the user from hazardous fumes
C. To measure pH
D. To mix reagents
Answer: B. To protect the user from hazardous fumes
Rationale: Fume hoods ventilate harmful vapors, ensuring safety during experiments.
10. When heating a liquid in a test tube, it should be:
A. Heated at one spot
B. Heated with a closed cap
C. Tilted and moved evenly over the flame
D. Placed directly on the flame without support
Answer: C. Tilted and moved evenly over the flame
Rationale: Moving the test tube prevents localized boiling and reduces the risk of splashing or
bursting.
,11. Which of the following is an indicator of a chemical reaction?
A. Change in temperature
B. Formation of gas
C. Color change
D. All of the above
Answer: D. All of the above
Rationale: Temperature change, gas evolution, and color change are common signs of chemical
reactions.
12. A solution with pH 3 is:
A. Neutral
B. Acidic
C. Basic
D. Alkaline
Answer: B. Acidic
Rationale: pH values below 7 indicate acidity, while above 7 indicate basicity.
13. Which glassware is most suitable for making solutions of precise concentrations?
A. Beaker
B. Volumetric flask
C. Test tube
D. Watch glass
Answer: B. Volumetric flask
Rationale: Volumetric flasks are calibrated for precise solution volumes, ensuring accurate
concentrations.
14. What is the purpose of a Bunsen burner in the lab?
A. To stir solutions
B. To provide a heat source
C. To measure liquids
D. To separate mixtures
Answer: B. To provide a heat source
Rationale: Bunsen burners provide controlled heat for chemical reactions and experiments.
15. Which method is used to purify a liquid by boiling and condensation?
A. Filtration
B. Evaporation
C. Distillation
D. Precipitation
Answer: C. Distillation
Rationale: Distillation separates components based on differences in boiling points.
16. The purpose of a crucible in the lab is to:
A. Heat substances to high temperatures
B. Measure liquid volume
C. Stir solutions
, D. Filter solids
Answer: A. Heat substances to high temperatures
Rationale: Crucibles are made of materials like porcelain or metal that withstand high heat.
17. Which is a primary standard?
A. NaOH
B. KHP
C. HCl
D. Acetic acid
Answer: B. KHP
Rationale: A primary standard is pure, stable, and has a known reaction stoichiometry, like
KHP.
18. A solution that conducts electricity is called:
A. Electrolyte
B. Nonelectrolyte
C. Solvent
D. Solute
Answer: A. Electrolyte
Rationale: Electrolytes dissociate into ions in solution, allowing electrical conductivity.
19. What is the purpose of rinsing a burette with the titrant before use?
A. Clean it
B. Prevent dilution of the titrant
C. Lubricate the tap
D. Increase volume
Answer: B. Prevent dilution of the titrant
Rationale: Rinsing with the titrant ensures accurate titration by avoiding contamination or
dilution.
20. Which of the following is a lab safety rule?
A. Eat in the lab
B. Keep long hair tied back
C. Pour water into acid
D. Ignore chemical spills
Answer: B. Keep long hair tied back
Rationale: Keeping hair tied prevents accidents like fire or contamination.
21. Which technique separates substances based on solubility differences?
A. Chromatography
B. Filtration
C. Recrystallization
D. Distillation
Answer: C. Recrystallization
Rationale: Recrystallization purifies solids by dissolving them and selectively crystallizing pure
compound.
VERIFIED ANSWERS PLUS RATIONALES | EXAM ALREADY
GRADED A+ | LATEST EXAM
1. Which piece of lab equipment is used to accurately measure 25.0 mL of liquid?
A. Beaker
B. Erlenmeyer flask
C. Volumetric pipette
D. Graduated cylinder
Answer: C. Volumetric pipette
Rationale: A volumetric pipette is calibrated to deliver precise volumes, making it ideal for
accurate measurements.
2. What is the purpose of a meniscus in liquid measurement?
A. To mix solutions
B. To indicate the volume accurately
C. To increase reaction rate
D. To prevent spillage
Answer: B. To indicate the volume accurately
Rationale: The meniscus forms at the liquid’s surface; reading the bottom of the meniscus
ensures accurate volume measurement.
3. Which chemical is commonly used to standardize a sodium hydroxide solution?
A. Hydrochloric acid
B. Potassium hydrogen phthalate (KHP)
C. Acetic acid
D. Sodium chloride
Answer: B. Potassium hydrogen phthalate (KHP)
Rationale: KHP is a primary standard that reacts stoichiometrically with NaOH, allowing
accurate titration.
4. During titration, the endpoint is reached when:
A. All the analyte is evaporated
B. The indicator changes color
C. The solution boils
D. The pH is 7
Answer: B. The indicator changes color
Rationale: The indicator signals the completion of the reaction by changing color at the
equivalence point.
5. Which technique is used to separate a solid from a liquid in a mixture?
A. Filtration
B. Distillation
,C. Chromatography
D. Titration
Answer: A. Filtration
Rationale: Filtration separates solids from liquids by passing the mixture through filter paper.
6. What safety equipment must be worn when handling strong acids?
A. Gloves and goggles
B. Apron only
C. Open-toed shoes
D. Face mask only
Answer: A. Gloves and goggles
Rationale: Gloves protect skin and goggles protect eyes from corrosive chemicals.
7. If a solution is diluted, what happens to its concentration?
A. Increases
B. Decreases
C. Remains the same
D. Doubles
Answer: B. Decreases
Rationale: Dilution adds solvent, lowering the solute concentration without changing the amount
of solute.
8. The density of a liquid can be calculated using:
A. Mass/volume
B. Volume × concentration
C. Mass × temperature
D. Pressure/volume
Answer: A. Mass/volume
Rationale: Density is defined as the mass per unit volume of a substance.
9. What is the function of a fume hood?
A. To heat solutions
B. To protect the user from hazardous fumes
C. To measure pH
D. To mix reagents
Answer: B. To protect the user from hazardous fumes
Rationale: Fume hoods ventilate harmful vapors, ensuring safety during experiments.
10. When heating a liquid in a test tube, it should be:
A. Heated at one spot
B. Heated with a closed cap
C. Tilted and moved evenly over the flame
D. Placed directly on the flame without support
Answer: C. Tilted and moved evenly over the flame
Rationale: Moving the test tube prevents localized boiling and reduces the risk of splashing or
bursting.
,11. Which of the following is an indicator of a chemical reaction?
A. Change in temperature
B. Formation of gas
C. Color change
D. All of the above
Answer: D. All of the above
Rationale: Temperature change, gas evolution, and color change are common signs of chemical
reactions.
12. A solution with pH 3 is:
A. Neutral
B. Acidic
C. Basic
D. Alkaline
Answer: B. Acidic
Rationale: pH values below 7 indicate acidity, while above 7 indicate basicity.
13. Which glassware is most suitable for making solutions of precise concentrations?
A. Beaker
B. Volumetric flask
C. Test tube
D. Watch glass
Answer: B. Volumetric flask
Rationale: Volumetric flasks are calibrated for precise solution volumes, ensuring accurate
concentrations.
14. What is the purpose of a Bunsen burner in the lab?
A. To stir solutions
B. To provide a heat source
C. To measure liquids
D. To separate mixtures
Answer: B. To provide a heat source
Rationale: Bunsen burners provide controlled heat for chemical reactions and experiments.
15. Which method is used to purify a liquid by boiling and condensation?
A. Filtration
B. Evaporation
C. Distillation
D. Precipitation
Answer: C. Distillation
Rationale: Distillation separates components based on differences in boiling points.
16. The purpose of a crucible in the lab is to:
A. Heat substances to high temperatures
B. Measure liquid volume
C. Stir solutions
, D. Filter solids
Answer: A. Heat substances to high temperatures
Rationale: Crucibles are made of materials like porcelain or metal that withstand high heat.
17. Which is a primary standard?
A. NaOH
B. KHP
C. HCl
D. Acetic acid
Answer: B. KHP
Rationale: A primary standard is pure, stable, and has a known reaction stoichiometry, like
KHP.
18. A solution that conducts electricity is called:
A. Electrolyte
B. Nonelectrolyte
C. Solvent
D. Solute
Answer: A. Electrolyte
Rationale: Electrolytes dissociate into ions in solution, allowing electrical conductivity.
19. What is the purpose of rinsing a burette with the titrant before use?
A. Clean it
B. Prevent dilution of the titrant
C. Lubricate the tap
D. Increase volume
Answer: B. Prevent dilution of the titrant
Rationale: Rinsing with the titrant ensures accurate titration by avoiding contamination or
dilution.
20. Which of the following is a lab safety rule?
A. Eat in the lab
B. Keep long hair tied back
C. Pour water into acid
D. Ignore chemical spills
Answer: B. Keep long hair tied back
Rationale: Keeping hair tied prevents accidents like fire or contamination.
21. Which technique separates substances based on solubility differences?
A. Chromatography
B. Filtration
C. Recrystallization
D. Distillation
Answer: C. Recrystallization
Rationale: Recrystallization purifies solids by dissolving them and selectively crystallizing pure
compound.
