+2
Barium has a positive charge of 2
Usually, a model is a depiction of a certain entity, never the real thing. In times
past, many, many models look great on paper but are way off!
Answer is: because pH value of solution is changing.
Balanced chemical reaction: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).
pH of sodium hydroxide solution is above seven (basic), when solution of hydrochloric acid is added, pH slowly dropping until it became neutral solution (pH is equal seven) and that is endpoint of titration.
Answer and Explanation:
(a) 
: its chemical name is sodium sulfate in which sodium is present as 
and sulfate is present as 
(b) 
: Its chemical name is copper nitrate which is a inorganic compound which is mostly crystalline in nature
(c)
: Its chemical name is iron carbonate or ferric carbonate
