Two solutions, initially at 24.60 degrees celsius are mixed in a coffee cup calorimeter (Ccal = 15.5 J/ degree celsius). 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 degrees celsius. Determine the delta Hrxn for the reaction as written below? Assume that the density and heat capacity of the solutions is the same as that of water.

NaCl(aq) + AgNO3(aq) --> AgCl(s) + NaNO3(aq)

a.) -35kJ b.)-250kJ c.)-69kJ d.)-16kJ e.)-140kJ

1 Answer
Nov 10, 2016

None of the options.


The heat capacity of water is 4.184 J/g-’C, Density is 1.0g/mL.
Given the initial concentrations, AgNO3 is the limiting reagent, so only 0.100M x 0.1L = 0.01 mole of compounds reacted. The temperature rise is (25.30 – 24.60) = 0.7‘C. The total mass of the solution is 200g, thus the amount of energy input to raise the solution temperature is:

200g * 4.184 J/g-’C = 836.8 J/’C.

Combining this with the heat absorbed by the calorimeter we get 836.8 + 15.5 = 852.3 J/’C.

Multiplying this value by the actual temperature increase gives us the total energy from the reaction as:

852.3 J/’C * 0.7’C = 596.61 Joules (0.5966 kJ)

Now we divide this number by the number of moles reacted (0.01) to get 59661 J/mole, or 59.7kJ/mol for the reaction.