Two solutions,initially at 24.69 °C,are mixed in a coffee cup calorimeter (C_cal = 105.5 J °C^-1).When a 200.0 mL volume of 0.100 mol L^-1 AgNO₃ solution is mixed with a 100.0 mL sample of 0.100 mol L^-1 NaCl solution,the temperature in the calorimeter rises to 25.16 °C.Determine the $D _ { \mathrm { r } }$ H°,in units of kJ $\mathrm { mol } ^ { - 1 }$ .Assume that the density and heat capacity of the solutions is the same as that of water. Hint: Write a balanced reaction for the process.

Question

Quizplus · Accepted Answer

The balanced reaction is AgNO3 + NaCl → AgCl + NaNO3. The heat absorbed by the calorimeter is q = C_cal * ΔT = 105.5 J/°C * (25.16°C - 24.69°C) = 49.755 J. The total volume of the solution is 300 mL, which is 0.3 kg assuming the density of water. The heat absorbed by the solution is q = m * c * ΔT = 0.3 kg * 4.18 kJ/kg°C * 0.47°C = 0.58974 kJ. The total heat change is the sum of these, which is approximately 0.639495 kJ. Since the reaction involves 0.01 mol of AgNO3 (limiting reactant), the ΔH° = -0.639495 kJ / 0.01 mol = -63.9495 kJ/mol, which rounds to -64 kJ/mol.

Two Solutions,initially at 24 DrD _ { \mathrm { r } }Dr​

Two Solutions,initially at 24 $D _ { \mathrm { r } }$