Q = m x c x ΔT

Q = heat gained

m = mass of substance = 12g

c = heat capacity of iron = 0.45J /g°C

ΔT = change im temperature = ( 210 -35) = 175°C

Now put all the given values in the above formula, we get the amount of heat required.

Q = 12g x 0.450J /g°C x 175°C

Q = 945J

Therefore, the amount of heat required is, 945J