Two solutions, initially at 24.60°C, are mixed in a coffee cup calorimeter. When a 100.0 mL volume of 0.100 M AgNO3 solution is mixed with a 100.0 mL sample of 0.200 M NaCl solution, the temperature in the calorimeter rises to 25.30°C. Determine the △ H°rxn in units of kJ/mol AgCl. Assume that the density and heat capacity of the solutions is the same as that of water. The specific heat capacity of water = 4.18 J/g°C.

58520kJ / mol

Explanation:

It is possible to obtain the heat produced in a reaction in a coffe cup calorimeter using the formula:

q = - C*m*ΔT

Where q is heat, C is specific heat capacity (4.18 J/g°C), m is mass of the solution (200,0 mL = 200,0g), and ΔT is change in temperature (25.30°C - 24.60°C = 0.70°C)

Replacing:

q = - 4.18J/g°C*200.0g*0.70°C

q = - 585.2J

In the reaction:

AgNO₃ (aq) + NaCl (aq) → AgCl (s) + NaNO₃ (aq)

Moles that react are:

0.1000L ₓ (0.100mol / L) = 0.0100 moles

The ΔH°rxn is defined as the heat released or consumed per mole of reaction. That is:

ΔH°rxn = - 585.2J / 0.01mol = 58520kJ / mol