What exactly is net ionic equation?
The molecular equation for this titration is $$\ce{K2Cr2O7 + 6Fe(NH4)2(SO4)2 + 7H2SO4 -&gt;
3Fe2(SO4)3 + Cr2(SO4)3 + K2SO4 + 6(NH4)2SO4 + 7H2O}$$

The complete ionic equation is $$\ce{2K+ + Cr2O7^2- + 6Fe^2+ + 12NH4+ + 19SO4^2- + 14H+ -&gt;
6Fe3+ + 14SO4^2- + 2Cr^3+  + 2K+  + 12NH4^+  + 7H2O}$$

When you cross out everybody who shows up on both sides in the same form, you get the net ionic equation for this titration: $$\ce{Cr2O7^2- + 6Fe^2+ + 14H+ -&gt; 6Fe^3+ + 2Cr^3+ + 7H2O}$$

Just as the hydrogens in $\ce{H2SO4}$ become $\ce{2H+}$ so the potassiums in  $\ce{K2Cr2O7}$ become $\ce{2K+}$ and they don't change on the other side of the equation where they form $\ce{K2SO4}$.