The strong Base with a pH of 12 is reduced by 4 units upon being added with solution Y. If you added a strong acid to the strong base, all ions are present in the solution, yes? So every OH- is neutralised by every H+ for example, meaning the resultant pH should be 7. The resultant pH is only 8 however, so solution Y must be a <em>weak acid </em>only!
It is the independent variable because you can ‘manipulate’ or ‘change’ it.
Explanation:
(1) CuF2+Mg-------->MgF2+Cu
(2) 2Na+2H2O --------> 2NaOH+H2
(3) 2KBr+Cl2-------->2KCl+Br2
