Question

When 0.638 g of Ca metal is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 104C is observed.
Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC.

The molar heat of reaction for the reaction of Ca(s) + 2H^+(aq) Ca^2+(aq) + H2(g)is _____kJ/mol.

Answer 1

Mass H2O x specific heat x delta T = q = heat evolved when 0.638 g Ca is reacted with HCl.
So q/0.638 will give you J/g
Convert that to J/mol.
Post your work if you get stuck.

Answer 2

Mass H2O x specific heat x delta T = q

200 g x [(4.184 J/gC)/18.02g] x 10.4 C = q
482.928 = q

q/0.638 --> 482.928/0.638 = 756.972 J/g

Is that right so far?