Question 1

How do you prepare a dilute nitric acid solution from concentrated acid?

Accepted Answer

Measure 32 mL of 15.7 M concentrated nitric acid and carefully pour it into a 1-L volumetric flask using a funnel. Add deionized water to the flask up to the mark and stir until homogeneous. This produces 1 L of 0.5 M nitric acid. Always handle nitric acid with appropriate personal protective equipment, including a lab coat, chemical splash goggles, and gloves, as it is toxic and corrosive.

Question 2

What is the correct procedure for preparing an iron(III) chloride solution?

Accepted Answer

Measure 125 mL of 0.5 M nitric acid into a 250-mL Erlenmeyer flask. Grind 33.79 g of iron(III) chloride hexahydrate to a fine powder using a mortar and pestle, then transfer it to the flask. Heat the mixture at approximately 80 °C while stirring until homogeneous. Cool to room temperature before transferring to a labeled brown glass bottle for storage in a corrosives cabinet.

Question 3

How do you prepare a sodium thiocyanate solution for Beer's Law experiments?

Accepted Answer

Measure 250 mL of 0.5 M nitric acid into a 250-mL Erlenmeyer flask. Weigh 10.1 mg of sodium thiocyanate using an analytical balance and add it to the flask. Stir at room temperature until the mixture appears homogeneous, creating a 0.5 mM sodium thiocyanate solution in 0.5 M nitric acid. Store in a labeled brown glass bottle in a corrosives cabinet.

Question 4

Why should solutions be stored in brown glass bottles?

Accepted Answer

Brown glass bottles protect solutions from light exposure, which can degrade light-sensitive compounds and affect experimental accuracy. This is particularly important for iron(III) chloride and sodium thiocyanate solutions used in spectrophotometric analysis, where light stability directly impacts measurement reliability and reproducibility of results.

Question 5

What glassware and equipment does each student workstation need for Beer's Law experiments?

Accepted Answer

Each pair of students requires two 50-mL burettes, volumetric pipettes (1-mL, two 5-mL, and 10-mL), a 50-mL volumetric flask, beakers of various sizes, graduated cylinders, funnels, a glass stirring rod, and a 3.5-mL cuvette with cap. A hand-held spectrophotometer and ring stand with burette clamp complete the setup for conducting Beer's Law measurements.

Question 6

How should the laboratory be prepared before students begin Beer's Law experiments?

Accepted Answer

Place waste containers and wash bottles filled with deionized water in satellite hoods. Distribute hand-held spectrophotometers to workstations and assemble ring stands with burette clamps. Set up each workstation with required glassware, lab equipment, and supplies including laboratory wipes, baking soda, pH paper, and disposable pipettes. Position prepared solutions in a central hood just before the lab begins.

Question 7

What safety precautions are essential when handling corrosive chemicals in this lab?

Accepted Answer

Wear appropriate personal protective equipment including a lab coat, chemical splash goggles, and gloves throughout the experiment. Handle nitric acid with extreme caution due to its toxic and corrosive nature. Store all corrosive solutions in labeled brown glass bottles in a corrosives cabinet. Neutralize any acid waste and follow standard glassware washing procedures after completing the experiment.

比尔定律

什么是化学平衡？

如何表示化学反应的平衡常数？

如何确定平衡浓度？

Browse More Videos