Given below are two statements, one is labeled as Assertion (A) and reason (R).

Assertion (A) : When $N{a}_{2}C{O}_3$ is treated against $HCl$ in presence of phenolphthalein indicator, it is converted to $NaCl.$ 

Reason (R) : Phenolphthalein shows colour change in the $pH$ range of $(3.5-4.6).$

When${\mathrm{Na}}_2{\mathrm{CO}}_3$​ reacts with HCl, the compound is neutralized in a step-wise manner, that is, ${\mathrm{NaHCO}}_3$​ is formed first before they are completely transformed to ${\mathrm{H}}_2{\mathrm{CO}}_3 (\mathrm{or} {\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}).$

$$\begin{gathered} {\mathrm{Na}}_2{\mathrm{CO}}_3+\mathrm{HCl}\to {\mathrm{NaHCO}}_3+\mathrm{NaCl}..........\left(\mathrm{I}\right) \\ {\mathrm{NaHCO}}_3+\mathrm{HCl}\to \mathrm{H}2{{\mathrm{CO}}_3}_{ }+\mathrm{NaCl}............\left(\mathrm{II}\right) \end{gathered}$$

In the presence of Phenolphthalein (ph) indicator, it only shows the(I) reaction. 

Phenolphthalein shows the colour change at pH 8.2 to 10.