*Reupload* Please help! 100 points! I've tried and it's hard to understand

For ai it's atomic number is 13 and it's mass number is 27 how many neutrons does it have

You encounter a solution that is acidic and you decide to test it by adding a small amount of a strong acid. the ph lowers slightly but is approximately unchanged, and still remains acidic. what can you say about the solution? a. it is a buffer solution. b. it is not a buffer solution it is a strong acid solution. d. the solution has been neutralized. e. the solution has excess acid present

All of the following are part of the biosphere except