What is one end of a magnetized compass's needle attracted to?

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

When water dissociates, each water molecule splits into a hydroxide ion and a) h 3 o + b) a hydrogen atom c) a hydrogen ion d) h 2 o e) oh —

Complete each row of the table below by filling in the missing prefix or missing exponent.