Question

Mass of Ca(s)	0.5 g
Volume of 1.0 M HCl	50.0 mL
initial temperature	25.8 C
final temperature	45.7 C

calculate the enthalpy of dissolution of Ca in acid in kJ/mol

Answer 1

Volume of HCl solution= 50.0 ml

The HCl solution is prepared in water. So, volume of water = 50.0 ml

density of water = 1 g/ml

So, mass of water = density*volume = 1*50.0 = 50.0 g

heat capacity of water = 4.184 J/g ^oC

temperature rise = 45.7-25.8 = 19.9 ^oC

So, heat evolved = mass*heat capacity*temperature rise = 50.0*4.184*19.9 = 4163 J = 4.163 kJ

Mass of Ca = 0.5 g

molar mass of Ca = 40 g/mol

moles of Ca = mass/molar mass = 0.5/40 = 0.0125 mol

So, enthalpy of dissolution = heat evolved/moles = 4.163/0.0125 = 333.04 kJ/mol