Calorimetry (section 5.2)

Question

Calculate qrxn for the reaction that occurs when 25.0 mL of 1.00 M HCl are added to 25.0 mL of 1.00 M NaOH in a coffee-cup calorimeter at room temperature (25.0o C). The final temperature of the solution was 31.4o C. Assume that the density of the solution is 1.00 g/mL and that Cs,soln is 4.18 J/g.o C.

Answer 1

Here we will use the expression q = mC∆T

q = heat = ?

m = mass = 25.00 ml + 25.00 ml = 50.00 ml x 1 g /ml = 50.00 g

C = specific heat = 4.18 J/gº

∆T = change in temperature = 31.4º - 25.0º = 6.4º

q = (50.00 g)(4.18 J/gº)(6.4)

q = 1338 J

This is the heat of the reaction. If you wanted to find this on a per mole basis, you'd need to divided by the number of moles present which would be 0.025 L x 1.00 mol / L = 0.025 moles.