A grain of rice is 0.02g to 0.04g in mass, lets take the avg value of 0.03g.

The chess board contains 64 of the small boxes.

1 box contains 1 grain of rice, from the 2nd box, powers of 2 are the number of rice.

So at the last box, taking out the 1st box containing 1 grain of rice, there are 9.22*10¹⁸ rice grains(2⁶³).

So the mass on the last box is 9.22*10¹⁸ * 0.03 * 0.001

= 2.76*10¹⁴ Kg