Question

Mass of metal=45.00 grams
Initial temp= 20.0 degrees Celcius
Final temp= 87.0 degrees Celcius

4.184 J/g-specific heat of H2O

The metal was heated up from initial temp to final temp. What would be the metal's highest temperature?

The specific heat of the metal was calculated to be 7.93x10^-1 J/g*degC

Answer 1

Also, another question I have is about enthalpy.

1. Calculate the standard enthalpy change for reaction at 25 deg C. Standard enthalpy formations of
Mg(OH)2(s) +2HCl(g) right arrow MgCl2(s) +2H2O (g)
What is the enthalpy of the rxn in kJ?

I'm calculating everything and got -385 . When I entered the answer it was wrong, so I'm unsure of where I went wrong.

Mg(OH)2(s)=-924.5
HCl(g)=-92.3
MgCl2=-641.3
H2O=-241.8

Answer 2

Your post is not well organized. I assume those temperatures at the top are Tinitial and Tfinal for H2O and not the meal.
[mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0

#2.
dS0 = (n*dSo products) - (n*dSo reactants)
Substitute and solve. Post your work if you want us to find the error.