Question

Zinc metal reacts with hydrochloric acid according to the following balanced equation. Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g) When 0.103 g of Zn(s) is combined with enough HCl to make 55.0 mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 21.7 ∘C to 24.4 ∘C.

Answer 1

Mass of solution = density * volume = 1.00 * 55.0 = 55.0 g.

Specific heat capacitiy of solution = 4.184 J/g.⁰C

Change in temperature = 24.4 - 21.7 = 2.7 ⁰C

Heat change = mass * specific heat capacity * change in temperature

q = 55.0 * 4.184 * 2.7

q = 621. J

And

Mass of Zn = 0.103 g.

Molar mass of Zn = 65.3 g/mol

Moles of Zn = mass / molar mass = 0.103 / 65.3 = 0.00158 mol

Therefore,

Enthalpy change per mol of Zn = q / n = 621. / 0.00158 = 393702 J / mol = 393.7 kJ/mol of Zn