Answer:
404 J
Explanation:
The amount of heat given off by the magnesium sample is given by:
[tex]Q=mC_s \Delta T[/tex]
where
m = 20.0 g is the mass of the sample
[tex]C_s = 1.01 J/gC[/tex] is the specific heat capacity of the magnesium
[tex]\Delta T=50.0 C-70.0 C=-20.0^{\circ}[/tex] is the change in temperature
Substituting into the equation, we find
[tex]Q=(20.0 g)(1.01 J/gC)(-20.0^{\circ})=-404 J[/tex]
and the negative sign means the heat is given off by the sample.
