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