Quiz: Laboratory Techniques and Safety — 11 questions

1. What role does a solvent play in a solution?

A. It separates microorganisms from the liquid through heating

B. It remains as the solid material dispersed through the mixture

C. It dissolves another substance without undergoing chemical change

D. It reacts with the dissolved substance to form a new compound

Answer: (C)

Explanation

A solvent is the liquid that dilutes or extracts another substance without chemically changing itself or the extracted material. The dissolved substance is called the solute, so describing the solvent as the dispersed solid confuses the two terms.

2. What is distilled water primarily characterized by?

A. Water that is naturally sourced from lakes or rivers without treatment.

B. Water that has been filtered through charcoal to remove organic contaminants.

C. Water obtained by boiling and condensation, removing most minerals, impurities, and microorganisms.

D. Water that contains dissolved minerals and ions, suitable for laboratory use.

Answer: (C)

Explanation

Distilled water is produced by boiling and condensation, which removes the majority of minerals, impurities, and microorganisms. The other options describe different types of water or are incorrect.

3. Which combination represents appropriate laboratory attire for a chemistry practical?

A. A plastic cape, face shield, bare legs, and cloth slippers

B. A loose coat, reading glasses, tights, and canvas shoes

C. A fastened cotton coat, goggles, trousers, and closed-toe shoes

D. An unfastened coat, sunglasses, shorts, and open sandals

Answer: (C)

Explanation

Appropriate attire includes a fastened cotton lab coat, chemistry safety goggles, trousers covering the legs, and closed-toe shoes, with long hair tied back. Open footwear is unsafe because it leaves much of the foot exposed, and ordinary sunglasses do not provide suitable chemical protection.

4. What is the primary method used to obtain distilled water in laboratories?

A. Boiling followed by condensation

B. Filtering through activated charcoal

C. Mixing tap water with distilled water

D. Freezing and thawing repeatedly

Answer: (A)

Explanation

Distilled water is obtained by boiling the water and then condensing the vapor, which removes most minerals, impurities, and microorganisms. Filtering or other methods do not achieve the same level of purity as distillation.

5. Which action follows the rules for handling solutions during a laboratory session?

A. Pipetting directly from a stock bottle with the bottle open

B. Returning excess solution to its original bottle after use

C. Pouring a solution into a beaker before pipetting it

D. Leaving an unidentified container on the bench during cleanup

Answer: (C)

Explanation

Solutions should be poured into a beaker before pipetting, while bottles should be closed immediately after use. Direct pipetting from a stock bottle and returning excess solution can contaminate the original supply, and unidentified containers must not remain on the bench.

6. What is the primary purpose of wearing safety goggles during laboratory work?

A. To keep the eyes warm in cold environments

B. To protect the eyes from chemical splashes and debris

C. To improve vision clarity for detailed tasks

D. To prevent light from entering the eyes during measurements

Answer: (B)

Explanation

Safety goggles are essential to protect the eyes from chemical splashes, debris, and other hazards. Wearing them does not primarily serve to improve vision clarity, prevent light entry, or keep eyes warm.

7. Which process produces distilled water in the laboratory?

A. Evaporation without collecting the vapor

B. Boiling followed by condensation

C. Decantation after mineral precipitation

D. Filtration through an ion-exchange resin

Answer: (B)

Explanation

Distilled water is produced by boiling water and then condensing the vapor, which removes most minerals, impurities, and microorganisms. Ion-exchange treatment instead describes a method associated with removing dissolved ions to produce demineralized water.

8. When should a volumetric flask be used in laboratory procedures?

A. To add reagents dropwise during titrations.

B. To prepare a solution of precise concentration from a solid or from a stock solution by dilution.

C. To measure approximate volumes of liquids for quick transfers.

D. To hold liquids temporarily during experiments with low accuracy requirements.

Answer: (B)

Explanation

A volumetric flask is used to prepare solutions of exact concentration by dissolving solids or diluting stock solutions. It is not intended for quick or approximate measurements, which are better suited to beakers or graduated cylinders.

9. How does a burette differ from a graduated cylinder in laboratory glassware?

A. A burette is used for heating liquids, while a graduated cylinder is used for mixing solutions.

B. A burette is made of glass and a graduated cylinder is made of plastic, affecting their chemical resistance.

C. A burette measures temperature changes, whereas a graduated cylinder measures volume.

D. A burette allows for the dropwise addition of reagents and measures volumes precisely, whereas a graduated cylinder provides approximate volume measurements.

Answer: (D)

Explanation

A burette is designed for precise, dropwise addition of reagents and accurate volume measurement, unlike a graduated cylinder which is used for approximate volume readings. The main difference lies in their purpose and precision.

10. Who is credited with the development of the micropipette as a precision instrument for dispensing micro-volumes?

A. The inventor of the micropipette is credited to the scientists who designed it for accurate micro-volume transfer.

B. The concept was proposed by biologists seeking to improve accuracy in small-volume measurements.

C. The development of the micropipette is attributed to laboratory instrument manufacturers who specialized in precision tools.

D. The micropipette was formulated by engineers working on miniaturized liquid handling devices.

Answer: (A)

Explanation

The micropipette was developed by scientists and engineers to provide precise control over micro-volume liquid transfers, crucial for molecular biology and biochemistry. The other options are plausible but less specific, as the invention is primarily credited to those who designed it for accuracy in small-volume handling.

11. What is the primary cause for choosing a micropipette with the largest capacity that still meets the required volume?

A. To reduce the risk of contamination during pipetting

B. To minimize the amount of residual liquid left in the tip

C. To ensure compatibility with various sample types

D. To maximize precision in dispensing small volumes

Answer: (D)

Explanation

Selecting a micropipette with the largest capacity that can deliver the required volume ensures greater accuracy and precision. Using a smaller capacity pipette for larger volumes can lead to less accurate measurements due to increased relative error.