\(\mathop {\mathop {HClO_3}\limits_{III} }\limits_{\left( {PKa = - 3} \right)} > \mathop {\mathop {{H_3}P{O_3}}\limits_{II} }\limits_{\left( {PKa = 1.3} \right)} > \mathop {\mathop {{H_2}S{O_4}}\limits_I }\limits_{\left( {PKa = 2} \right)} \)
${H_2}O + B{r_2} \to HOBr + HBr$