Introduction:
Solving previous years' papers of UPSC Chemistry optional can indeed help in improving the ability to write concise and coherent answers. This practice not only familiarizes candidates with the pattern and style of questions asked in the exam but also enhances their understanding of the subject matter.

1. Understanding the Question Pattern:
By solving previous years' papers, candidates can get a clear idea of the types of questions that are frequently asked in the UPSC Chemistry optional exam. They can identify the recurring themes and topics, which will help them focus their preparation accordingly. This understanding of the question pattern enables candidates to anticipate the requirements of each question and structure their answers accordingly.

2. Developing Concise Answers:
One of the key skills required in the UPSC exam is the ability to provide concise answers that directly address the question. By practicing with previous years' papers, candidates can learn to identify the core concepts and key points that need to be included in their answers. This practice helps in avoiding unnecessary elaboration and ensures that the answers are to the point, saving valuable time in the exam.

3. Enhancing Coherence:
Coherence in the answers refers to the logical flow of information and ideas. Solving previous years' papers allows candidates to analyze the structure and organization of well-constructed answers. They can observe how different points are linked together, how transitions are made between paragraphs, and how the overall flow of information is maintained. This practice helps candidates in developing a coherent writing style and ensures that their answers are logically structured.

4. Improving Time Management:
Time management is crucial in the UPSC exam, and practicing with previous years' papers can significantly improve this skill. By solving these papers under timed conditions, candidates can learn to allocate their time effectively for each question. This practice helps them in developing a strategy to quickly identify the key points, prioritize their answers, and write concise responses within the given time frame.

Conclusion:
Solving previous years' papers of UPSC Chemistry optional is an effective strategy to improve the ability to write concise and coherent answers. This practice enables candidates to understand the question pattern, develop concise answers, enhance coherence, and improve time management skills. By consistently practicing with these papers, candidates can boost their confidence and perform better in the UPSC Chemistry optional exam.