List the following molecules in order of increasing bond order: 1. C=C 2. C-C 3. CΞC

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Question: List the following molecules in order of increasing bond order:
1. C=C
2. C-C
3. C≡C

Option analysis:
- Option a: 1,3,2. This sequence places C=C first (bond order 2), then C≡C (bond order 3), and finally C-C (bond order 1). Since the bond orders should increase from smallest to largest, this ordering incorrectly starts with a higher bond order (2) before the lowest (1). It mixes up the relative strengths, so this option is not correct.
- Option b: 3,1,2. Here the order begins with C≡C (3), then C=C (2), then C-C (1). This is decreasing rather than increasing, since bond order drops from 3 to 2 to 1 as you move along, so the sequence violates the required increasing trend.
- Option c: 2,3,1. This puts C-C (1) after C=C (2) and C≡C (3) at the end. Although it ends with the strongest bond, the middle position has the strongest bond as well, which breaks the monotonic increase expected from smallest to largest bond order. Therefore this option is not valid.
- Option d: 2,1,3. This sequence starts with C-C (1), followed by C=C (2), and ends with C≡C (3). Each step increases in bond order, which matches the concept that bond order reflects the number of shared electron pairs: a single bond (1) < double bond (2) < triple bond (3). This option correctly follows the increasing trend.
- Option e: 1,2,3. This ordering lists C=C (2) first, then C-C (1), then C≡C (3). The first transition goes from 2 to 1 (decrease), which violates the increasing order requirement. Thus this option is incorrect.
- Option f: 3,2,1. This is a strictly decreasing sequence, beginning with the triple bond and ending with the single bond. Since the task asks for increasing bond order, this option is definitively incorrect.

Conceptual note:
- Bond order is a count of bonding interactions between two atoms in a bond; higher bond order generally corresponds to a stronger, shorter bond. Among C-C, C=C, and C≡C, the bond orders are 1, 2, and 3 respectively. The correct increasing order is 1 < 2 < 3, which corresponds to the sequence C-C, then C=C, then C≡C.

Summary:
- The only option that preserves a consistent rise in bond order from left to right is the sequence where a single bond comes first, followed by a double bond, and finally a triple bond. All other options fail to maintain monotonic increase in bond order across the three species.

CHM1051 MUM S2 2025 CHM1051 Practice Exam 2

List the following molecules in order of increasing bond order: 1. C=C 2. C-C 3. CΞC

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