Neutralisation of NaOH by HCl: (3): The reaction seen with an indicator
Litmus allows to distinguish between chlorhydric acid (red, left) and sodium hydroxide (blue, right).
A solution of sodium hydroxide colored by litmus.
A small quantity of chlorhydric acid is added. The beaker is shaken.
The blue colour has remained.
So $HCl$ has completely disappeared, otherwise the color would have changed to red. A chemical reaction took place!!!
An excess of chlorhydric acid is added. $NaOH$ has disappeared completely, otherwise the blue color would have persisted. It is thus confirmed that a chemical reaction took place !!
$Na^+ + $ $OH^- + H^+$$ + Cl^- \longrightarrow $$H_2O$$ + Na^+ + Cl^-$
Products: water and a solution of sodium chloride !
