Question

Calculate the enthalpy change for the isomerization of pentene-1 to pentene-2 if 2.5 g of pentene-1 is isomerized using a catalyst and the temperature increases from 25° C to 35° C. The heat capacity of the calorimeter is 15.6 J/deg and the density of the solution is 0.98 g/mL. Assume the heat capacity of the solution is equal to the heat capacity of water (4.18 J/g deg).

Answer 1

To calculate the enthalpy change for the isomerization of pentene-1 to pentene-2, we need to determine the heat absorbed by the solution and the calorimeter during the reaction.First, let's calculate the heat absorbed by the solution:q_solution = mass_solution  heat_capacity_solution  TSince the density of the solution is 0.98 g/mL, we can find the volume of the 2.5 g of pentene-1:volume = mass / density = 2.5 g / 0.98 g/mL = 2.551 mLAssuming the volume of the solution is approximately equal to the volume of pentene-1, we can find the mass of the solution:mass_solution = volume  density = 2.551 mL  0.98 g/mL = 2.5 gNow, we can calculate the heat absorbed by the solution:q_solution = mass_solution  heat_capacity_solution  Tq_solution = 2.5 g  4.18 J/g C   35 C - 25 C q_solution = 2.5 g  4.18 J/g C  10 Cq_solution = 104.5 JNext, let's calculate the heat absorbed by the calorimeter:q_calorimeter = heat_capacity_calorimeter  Tq_calorimeter = 15.6 J/C   35 C - 25 C q_calorimeter = 15.6 J/C  10 Cq_calorimeter = 156 JNow, we can find the total heat absorbed during the reaction:q_total = q_solution + q_calorimeterq_total = 104.5 J + 156 Jq_total = 260.5 JFinally, we can calculate the enthalpy change for the isomerization of pentene-1 to pentene-2 per gram of pentene-1:H = q_total / mass_pentene-1H = 260.5 J / 2.5 gH = 104.2 J/gThe enthalpy change for the isomerization of pentene-1 to pentene-2 is 104.2 J/g.