To calculate the relative formula mass of Nitrate (NO3-), we add the relative atomic masses of each atom in the formula.

Nitrogen (N) has a relative atomic mass of 14.01.

Oxygen (O) has a relative atomic mass of 16.00.

In nitrate (NO3-), we have one Nitrogen atom, and three Oxygen atoms.

Relative Formula mass of Nitrate (NO3-) = (1 x 14.01) + (3 x 16.00)

= 14.01 + 48.00

= 62.01

Therefore, the relative formula mass of nitrate is approximately 62.01.