Chemistry
The picture given below shows an apparatus that a teacher used for demonstrating the properties of ionic substances. The teacher heats a sample of lead bromide in a crucible which contains two electrodes which are part of the circuit shown. The bulb does not light up. What is the best explanation for this?
- The circuit is complete.
- Molten lead bromide does not conduct electricity.
- The sample of lead bromide was not heated up to the melting point by the teacher.
- The DC power supply was set up correctly.
Answer
The sample of lead bromide was not heated up to the melting point by the teacher.
Reason — To conduct electricity the crucible containing lead bromide should be heated above 380°C, the melting point of Lead bromide. Solid lead bromide is a non-conductor of electricity, since its ions are not free. The ions become free when lead bromide is in the fused or molten state. Thus, in the above experiment the sample of lead bromide was not heated up to the melting point by the teacher. So, the bulb does not light up.
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