Introduction:
Ethanol and ethanoic acid are two different compounds with similar chemical structures. To distinguish between the two, certain substances can be used based on their chemical reactivity. In this response, we will discuss the substances mentioned in the options and determine which one cannot be used to distinguish ethanol from ethanoic acid.

Substances for distinguishing ethanol from ethanoic acid:

1. Na metal:
- Sodium metal reacts vigorously with ethanol, producing hydrogen gas and sodium ethoxide.
- However, sodium metal does not react with ethanoic acid, as it is a weak acid.
- Therefore, the reaction with sodium metal can be used to distinguish ethanol from ethanoic acid.

2. NaHCO3:
- Sodium bicarbonate (NaHCO3) is commonly known as baking soda.
- It reacts with ethanoic acid, producing carbon dioxide gas, water, and sodium acetate.
- This reaction does not occur with ethanol.
- Hence, the reaction with NaHCO3 can be used to differentiate between the two compounds.

3. Hot alkaline KMnO4 solution:
- Potassium permanganate (KMnO4) in an alkaline medium is a strong oxidizing agent.
- It oxidizes ethanol to ethanoic acid, resulting in a color change from purple to colorless or brown.
- Ethanoic acid itself does not undergo any significant reaction with KMnO4.
- Thus, the hot alkaline KMnO4 solution can be used to distinguish ethanol from ethanoic acid.

4. Hot acidified K2Cr2O7 solution:
- Potassium dichromate (K2Cr2O7) in an acidic medium is also a strong oxidizing agent.
- It oxidizes ethanol to ethanoic acid, leading to a color change from orange to green.
- Ethanoic acid does not undergo any significant reaction with K2Cr2O7.
- Therefore, the hot acidified K2Cr2O7 solution can be used to differentiate between ethanol and ethanoic acid.

Substance that cannot be used:

The substance that cannot be used to distinguish ethanol from ethanoic acid is NaHCO3.

Explanation:
Both ethanol and ethanoic acid react with NaHCO3, producing carbon dioxide gas. As a result, this reaction cannot be used to differentiate between the two compounds. It is important to note that while NaHCO3 can be used to distinguish ethanol from ethanoic acid, it is not the correct option in this scenario.

In conclusion, all the substances mentioned in the options, except NaHCO3, can be used to distinguish ethanol from ethanoic acid based on their specific reactions with the compounds.

hich ya whichphlae ya bolo