The reaction of formic acid with concentrated${\mathrm{H}}_2{\mathrm{SO}}_4$ gives

When you heat formic acid in presence of concentric sulphuric acid, you get a mixture of carbon monoxide gas and water vapors.

$\mathrm{HCOOH}\frac{\text{ conc }{\mathrm{H}}_2{\mathrm{SO}}_4}{\mathrm{\Delta }}\mathrm{CO}+{\mathrm{H}}_2\mathrm{O}$

In the above reaction, the concentrated sulphuric acid acts as a dehydrating agent.