To synthesize a protein how many water molecules per amino acids used?

Zero water molecules !
becozz a water molecule is formed per peptide bond formation ...not used!!
hope it helps

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).