Answer: The metal is Calcium.
Explanation:
To calculate the specific heat of substance during the reaction.
[tex]q=m\times c\times \Delta T[/tex]
where,
q = heat absorbed = 789.75 J
c = specific heat of metal = ?
m = mass of substance = 18.0 g
[tex]\Delta T_f[/tex] = final temperature - initial temperature = [tex](89.0-21.5)^0C=67.5^0C[/tex]
Now put all the given values in the above formula, we get:
[tex]789.75J=18.0g\times c\times 67.5^0C[/tex]
[tex]c=0.65J/g^0C[/tex]
As specific heat is characteristic of each metal and thus the metal is calcium which has specific heat of [tex]0.65J/g^0C[/tex]