Thermochemistry

Question

A 100.0 mL volume of 1.0 mol/L hydrochloric acid was mixed with 100.0 mL of 1.0 mol/L sodium hydroxide at 23.5 °C in a coffee cup calorimeter. After the reactants mix, the temperature increases to 30.6°C.The specific heat capacity of water is 4.18 J/g°C.How much energy (in kJ) is released in this reaction? Give the quantity and the unit (e.g. 3.5 cm).

Answer 1

A couple of assumptions need to be made to answer this question.

First, we must assume that the density of the solutions is the same as water, i.e. 1 g/ml

Next we must assume that no heat is lost to the surroundings.

Finally, assume specific heat of solution is same as specific heat of water

q = mC∆T

q = heat = ?

m = mass = 100 ml + 100 ml = 200 ml x 1g/ml = 200g

C = specific heat = 4.18 J/g/degree

∆T = change in temperature = 30.6 - 23.5 = 7.1 degrees

q = (200 g)(4.18 J/g/degree)(7.1 degrees)

q = 5,936 J = 5.94 kJ (3 significant figures)