CHROMIUM, \[CR{{O}_{5}}\] which is unstable.\[\begin{align} & {{K}_{2}}C{{r}_{2}}{{O}_{7}}+{{H}_{2}}S{{O}_{4}}\to {{K}_{2}}S{{O}_{4}}+{{H}_{2}}C{{r}_{2}}{{O}_{7}} \\& \LEFT[ {{H}_{2}}{{O}_{2}}\to {{H}_{2}}O+[O] \right]\times 4 \\& {{H}_{2}}C{{r}_{2}}{{O}_{7}}+4\,[O]\to 2Cr{{O}_{5}}+{{H}_{2}}O \\& \overline{\underline{{{K}_{2}}C{{r}_{2}}{{O}_{7}}+{{H}_{2}}S{{O}_{4}}+4{{H}_{2}}{{O}_{2}}\to 2Cr{{O}_{5}}+{{K}_{2}}S{{O}_{4}}+5{{H}_{2}}O}} \\\end{align}\]