The balanced chemical equation for the reaction between K2Cr2O7, H2SO4, and C3H8O3 is:

K2Cr2O7 + H2SO4 + C3H8O3 → Cr2(SO4)3 + CO2 + H2O + K2SO4

In order to balance the equation, coefficients are added to the reactants and products. The coefficients are adjusted so that the number of atoms of each element is the same on both sides of the equation.

In this case, the coefficients are:

1 K2Cr2O7

1 H2SO4

1 C3H8O3

1 Cr2(SO4)3

3 CO2

3 H2O

1 K2SO4

With these coefficients, the equation is balanced.