Question detail
Which practice best avoids contamination when several students use the same stock bottle of sodium carbonate solution?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
AS practical skills and required practical activities
Question
- A. A. Pour a small amount into a clean labelled beaker and never return unused solution to the stock bottle.
- B. B. Dip a used pipette back into the stock bottle after rinsing it with tap water.
- C. C. Share one unlabelled beaker between groups so less glassware is needed.
- D. D. Pour any leftover solution back into the stock bottle if it still looks clear.
Answer
A. Pour a small amount into a clean labelled beaker and never return unused solution to the stock bottle.
Explanation
Safe handling includes preventing contamination as well as preventing direct harm. Decanting a small amount into clean labelled apparatus protects the shared reagent and supports reliable practical results. Used pipettes, unlabelled shared vessels and returning leftovers can introduce impurities that affect later observations or measurements. This directly supports the learning objective to handle solids and liquids safely, including hazardous substances, because it links safe transfer, labelling, exposure control and contamination control to the practical context.
Common mistake
Improper Handling of Hazardous Substances
Students often forget to wear appropriate personal protective equipment (PPE) when handling hazardous solids and liquids, leading to safety risks.
Always wear gloves, goggles, and a lab coat when handling hazardous substances. This ensures safety and minimizes exposure to harmful chemicals.
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