Question

Manganese reacts with hydrochloric acid to produce manganese(II) chloride and hydrogen gas. Mn(s)+2HCl(aq) → MnCl2(aq)+H2(g). When 0.605 g Mn is combined with enough hydrochloric acid to make 100.0 mL of solution in a coffee-cup calorimeter, all of the Mn reacts, raising the temperature of the solution from 23.2 ∘C to 28.7 ∘C. Find ΔHrxn for the reaction as written. (Assume that the specific heat capacity of the solution is 4.18 J/g∘C and the density is 1.00 g/mL.)

Answer 1

mass of solution = volume * density

                             = 100*1 = 100g

q = mcT

     = 100*4.18*(28.7-23.2)

    = 2299J

no of moles of Mn   = W/G.A.wt

                                 = 0.605/55   = 0.011 moles

Mn(s)+2HCl(aq) → MnCl2(aq)+H2(g).

energy converted to J to J/mole

ΔHrxn   = 2299J/0.011mole    = 209000J/mole   = 209KJ/mole >>>>answer