Question 1

Why is an ice bath necessary when preparing Jones reagent?

Accepted Answer

The reagents undergo exothermic reactions when mixed, releasing significant heat. An ice bath keeps the chromium trioxide and sulfuric acid cool during their combination, preventing dangerous temperature spikes and potential splashing. The mixture must remain chilled throughout preparation to ensure safe handling and proper reagent formation.

Question 2

What safety precautions should you take before preparing alcohol identification reagents?

Accepted Answer

Put on a lab coat, safety glasses, and nitrile gloves before starting. Work in a fume hood because the reagents are acidic, toxic, and corrosive. Set up a waste container for aqueous chromium, iron, and zinc waste. These precautions protect you from hazardous chemical exposure during reagent preparation.

Question 3

How do you prepare 0.03 M iron(III) chloride solution?

Accepted Answer

Weigh 0.5 g of anhydrous iron(III) chloride and place it in a 250-mL beaker settled in an ice bath. Add 100 mL of deionized water and stir with a medium stir bar until completely dissolved. Transfer the cooled solution to a labeled brown glass bottle and store it in a cool, dark acid cabinet.

Question 4

What is the correct procedure for combining chromium trioxide and sulfuric acid in Jones reagent preparation?

Accepted Answer

Place 25 g of chromium trioxide in a beaker on an ice bath. Slowly add 25 mL of 98% sulfuric acid, starting to stir only after enough acid covers the stir bar. Continue stirring carefully to avoid splashing until the chromium trioxide dissolves completely. This controlled addition prevents dangerous exothermic reactions.

Question 5

How should you quench residual Jones reagent before cleaning glassware?

Accepted Answer

With the beaker in an ice bath, slowly add 10–20 mL of water and rinse residues along the beaker sides. Then slowly add cyclohexanol until the solution lightens in color. This quenching process neutralizes the highly toxic and corrosive hexavalent chromium before you wash the glassware.

Question 6

What are the steps for preparing Lucas reagent?

Accepted Answer

Pour 47 mL of 37% hydrochloric acid into a beaker on an ice bath and begin stirring. Slowly add 76.9 g of anhydrous zinc chloride, pausing as needed for cooling. Continue stirring until the zinc chloride dissolves completely and the solution cools to room temperature, then transfer to a labeled bottle with an acid-resistant cap.

Question 7

What glassware and equipment should be set up at each student workstation?

Accepted Answer

Each pair of students needs 13 small test tubes, a test tube rack, three small vials with caps, a 50-mL beaker, a 250-mL beaker, a 5-mL graduated cylinder, a glass stirring rod, labels or lab tape, and a labeling pen. A 250-mL wash bottle with deionized water and pipette bulbs should also be available at each station.

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