Acid Dilution and Spill Response in a Crowded Lab
During a 50-minute laboratory period, 26 students in four groups are preparing 1.8 L of 1.0 M sulfuric acid from 18 M stock. Each group receives 100 mL of the concentrated acid in a labeled beaker and a 2 L volumetric flask. The room has bench-top workspace, running water, an eyewash, and a safety shower, but no fume hood at the stations. The spill kit contains sodium bicarbonate, citric acid, vermiculite, tongs, and universal pH paper. One group has already begun by pouring about 50 mL of water into a beaker containing the 100 mL of 18 M acid; the mixture is visibly warm, and a drop spattered onto a student's glove. Another group has just spilled about 2 mL of the concentrated acid on the bench. Only 18 minutes remain, and the teacher wants the class to finish the dilution and use the acid in a follow-up reaction.
1. Evaluate the mixing order the first group used and describe how the teacher should direct the safe preparation of 1.8 L of 1.0 M H2SO4 from 100 mL of 18 M stock.
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The group's order is unsafe: adding water to concentrated sulfuric acid can produce local boiling and spattering because the heat of dilution is released into a small water layer. The correct approach is to add acid slowly to water, not water to acid. The dilution factor is 18, so 100 mL of 18 M stock diluted to 1.80 L gives 1.0 M. Practically, the teacher should have students place about 1.5 L of distilled water in a heat-resistant beaker, add the 100 mL of acid in small portions with gentle stirring, and cool the mixture in an ice bath between additions. After the mixture cools, transfer it to the 2 L volumetric flask and dilute to the mark. Goggles, gloves, and aprons are required throughout. The volumetric flask should not be used as the initial mixing vessel if it is not heat-resistant. The teacher should stop the group that reversed the order, inspect the beaker for cracks, and restart only after the mixture has cooled and been properly diluted.
2. Sequence the immediate response to the contaminated glove and the 2 mL bench spill, and justify the first action and the choice of neutralizing agent.
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People come before property. The student wearing the contaminated glove should remove it immediately, wash the hand and forearm with copious water for at least 15 minutes, and be checked by the teacher or nurse for burns or redness. If acid reached skin, continue washing and use the safety shower if needed. Only after the student is safe should the teacher isolate the bench area, put on gloves and goggles, and ventilate the area. For a 2 mL spill of 18 M acid, the teacher should cover the liquid with vermiculite or another inert absorbent first, then apply sodium bicarbonate solution to the absorbed residue and check with pH paper. Directly adding bicarbonate to concentrated acid can foam or spatter, so absorption before neutralization is the safer sequence. Citric acid is for base spills and is not appropriate here. The neutralized residue should be swept into a labeled hazardous-waste container, and the bench should be washed and rechecked with pH paper before students return.
3. The teacher must decide whether the class can continue. Identify two pieces of evidence that would support continuing and one condition that would require stopping.
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Continuing is defensible only if the contaminated student has no skin injury after washing, the spill area is contained and neutralized to near-neutral pH, and the room has adequate ventilation and supervision. Two supporting pieces of evidence would be a clear pH check near 7 on the bench after cleanup and a student who reports no pain, redness, or blistering after the 15-minute wash. A third would be that the remaining acid stock is secured and the group that mixed incorrectly has been redirected. Stopping is required if the student shows any sign of chemical burn, if acid reached the eyes or a large skin area, if vapors cause coughing or eye irritation, or if the teacher cannot maintain direct supervision of both the injured student and the remaining groups. The 18-minute remaining time is not itself a reason to continue; the teacher should shorten or postpone the follow-up reaction rather than rush acid handling.