Question

When 0.100 g Zn(s) combines with enough HCl to make a total of 55.0 mL solution in a coffee cup calorimeter, all of the zinc reacts, which increases the temperature of the HCl solution from 23.0∘C to 24.5 ∘C: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) Calculate the enthalpy change of the reaction ΔHrxn. (Assume the density of the solution is 1.00 g/mL and the specific heat capacity of solution is 4.184 J/g∘C.) in J/mol. (Enter answer in numerical form without J or KJ after the number.)

Answer 1

Q = mc∆T

Q = heat energy (Joules, J), m = mass of a substance (kg)

c = specific heat (units J/kg∙K), ∆ is a symbol meaning "the change in"

∆T = change in temperature

Using above formula we can calcuate how much heat is realsed from the reaction

m = 55 ml = 55 gm

∆T = 24.5 - 23 = 1.5 Deg Cel

The amount heat realesed = 55 x 4.18 x 1.5 = 344.85 Joules

Now let us calculate the moles of Zinc

Atomic mass of Zinc = 65.38

Moles of Zinc = 0.1 / 65.38 = 0.001529 Moles

0.001529 Moles of Zinc generated 344.85 Joules of heat one mole of zinc (Enthalpy change) will be realesed

Enthalpy change = 344.85 x 1 / 0.001529 = 225462.9 Joules or 225.46 Kilo Jolues