In this equation except H2O, all are ionic in nature. Representing these compounds in ionic forms,
2K++Cr2O2−7+14H++7SO2−4+6Fe2++6SO2−4→6Fe3++9SO2−4+2Cr3++3SO2−4+2K++SO2−4+7H2O
2K+ ions and 13SO2−4 ions are common on both sides, so these are cancelled. The desired ionic equation reduces to the following equation
Cr2O2−7+14H++6Fe2+=6Fe3++2Cr3++7H2O
Total charges are equal on both sides; thus, the balanced ionic equation is the same as above.