Which one of the following pairs is correct? Compound with the lower chemical energy per mole Compound with the lower activation energy of combustion per mole A - VCE - SSCE Chemistry - Question 27 - 2020 - Paper 1

To determine which pair of compounds has the correct relationship regarding lower chemical energy and lower activation energy of combustion, we must analyze each option based on the understanding of chemical structures and energies.

1. Option A: ethanoic acid and methyl methanoate - Ethanoic acid has a lower energy than methyl methanoate when considering the structural aspects and formation energies, thus this may suggest it could have a higher activation energy for combustion.

2. Option B: ethanoic acid and ethanoic acid - This option is invalid because both substances are identical.

3. Option C: methyl methanoate and methyl methanoate - Similar to option B, this option is invalid due to identical compounds.

4. Option D: methyl methanoate and ethanoic acid - Here, methyl methanoate typically has a higher chemical energy compared to ethanoic acid as it contains an ester group, which generally has lower activation energy than acids during combustion.

Through this analysis, we conclude that Option B (ethanoic acid and ethanoic acid) is also incorrect because it fails to relate two different substances.

Based on these evaluations, the correct answer is Option B.