Question

Calorimetry and Standard Enthaply question: Manganese reacts with sulfuric acid to produce manganese (II) sulfate and hydrogen gas.

Mn(s) + H2SO4(aq) ---> MnSO4(aq) + H2(g) When 1.230g of Mn is combined with enough sulfuric acid to make 100.0mL of solution in a Thermo bottle calorimeter (heat capacity is 58.9 J/°C), all of the Mn reacts raising the temperature of the solution from 24.1°C to 34.5°C. (Assume that the specific heat capacity of the solution is 4.18 J/g°C and the density is 1.02g/mL.)

A) Is this reaction exothermic?

B) What is the heat (q) in Kg for the reaction according to the process described above?

C) Find ∆H°rxn for the chemical reaction as written above.

D) Consider the above given reaction. How many grams of manganese are needed if 895.0kJ of heat are released?

Answer 1

A) The reaction is exothermic , since solution tempertaure increased which shows absorbtion of heat released in reaction by solution.

B) Heat absorbed by solution = specific heat of solution x mass of solution x temp change

          = 4.18 x 102 x ( 34.5-24.1)        ( mass = vol x density = 100 x 1.02 = 102 g)

        = 4434.14 J

Heat absorbed by calorimeter = heat capcity of calorimeter x temp change

        = ( 58.9 ) x ( 34.5-24.1) = 615.56 J

Total heat absorbed by solution and calorimert = 4434.14+615.66 = 5046.7 J

This is heat released in reaction = 5046.7 J = 5.0467 KJ

C) moles of Mn = mass of Mn / atomic mass of Mn = 1.23 / 54.938 = 0.022389

delta H reaction = 5.0467 KJ / 0.022389 moles = 225.4 KJ/mol

D) gibe heat 895 , moles of Mn = ( heat / dH) = 895 /225.4 = 3.97

Mn mass = moles of Mn x atomic mass of Mn = 3.97 x 54.938 = 218.14 g