54. (i) The compound A has the following percentage composition by mass: carbon 26.7%, oxygen 71.1%, hydrogen 2.2%. Determine the empirical formula of A. (Work to one decimal place) (H = 1; C = 12; O = 16).   55. (ii) If the relative molecular mass of A is 90, what is the molecular formula of A?   56. (iii) The compound A is weak acid. What is meant by this statement?