Question

Zinc metal reacts with hydrochloric acid according to the following balanced equation. Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g) When 0.119 g of Zn(s) is combined with enough HCl to make 53.4 mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 21.7 ∘C to 24.5 ∘C. Part A Find ΔHrxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g⋅∘C as the specific heat capacity.)

Answer 1

Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g)

No of mol of Zn reacted = 0.119/65.5 = 0.00182 mol

heat released during the reaction(q) = m*s*DT

   m = mass of solution = v*d + zinc mass
   
      = 53.4*1+0.119 = 53.52 g

   S = specific heat capacity of solution = 4.18 j/g,c

   DT = 24.5 - 21.7 = 2.8

q = 53.52*4.18*2.8

     = 626.4 joule

     = 0.6264 kj

Part A

DHrxn = -q/n = -0.6264/0.00182 = -344.176 kj/mol