5. Which of the following shows the absence of oxygen in a material? a. combustion b. Lighted candle covered with glass c. Rusting
Answer (1)
The correct answer is b. Lighted candle covered with glass.When a lighted candle is covered with a glass, the oxygen inside the glass is gradually used up, and since no new oxygen can enter, the flame eventually goes out. This indicates the absence of oxygen in the enclosed space.Combustion (a) requires oxygen to occur, so it does not show the absence of oxygen; it shows oxygen is present and reacting.Rusting (c) is caused by the presence of oxygen reacting with iron, so it also indicates oxygen is present.
