(Im)Possible?

yes pretty easily in my experience

It is possible to get an A in 2 A level subjects (Maths and Chemistry) in a month from Cs, but it will be very difficult. You will need to be very dedicated and disciplined in your studies. You will also need to make sure that you are well-rested and healthy, as you will be putting a lot of strain on your mind and body.

Here are some tips that may help you:

Create a study schedule and stick to it. Make sure to allocate enough time for each subject, and don't forget to include breaks in your schedule.
Find a study partner or group. Studying with others can help you stay motivated and on track.
Use online resources and practice questions. There are many resources available online that can help you prepare for your exams.
Get enough sleep and eat healthy foods. Your physical and mental health are important, so make sure to take care of yourself.
Don't give up! It will be tough, but if you stick with it, you can achieve your goal.
Here are some additional tips that may help you:

Start by reviewing the basics. Make sure you have a solid understanding of the fundamental concepts in each subject.
Focus on your weaknesses. Identify the areas where you need more practice, and make sure to spend extra time on those topics.
Don't be afraid to ask for help. If you're struggling with a particular concept, don't be afraid to ask your teacher, tutor, or a friend for help.
Take practice exams. This is a great way to get a feel for the format of the exams and to identify areas where you need more practice.
Stay positive and motivated. It's important to stay positive and motivated, even when things get tough. Remember, you can do this

creating study schedules are a complete waste of time, dont bother doing that if you really far behind, just write a quick list of all the papers you want to get done. Just do as many past papers as possible - dont do anything else - this is by far the best method to boost your marks.