The thermochemistry base equation is
Q = Heat in Joules
m = mass of the material
T = change in Temperature
- For this equation the metal is going to lose heat make Q negative while the water is going to gain heat making Q positive
Due to the Law of Conservation of Energy the heat lost by the metal will be equal to the heat gained by the water.
#-Q_(Cr) = +Q_(water)#
specific heat of water is 4.18 J/gC
specific heat of iron is 0.45 J/gC
We will assume that water boils at 100 C and that is the initial temp of the chromium.
I hope this was helpful.