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

total volume of the solution = 25 + 25 = 50 mL

density of the solution = 1 g / mL

mass = density x volume

          = 1 x 50

          = 50 g

dT = T2 - T1

       = 31.4 -25

        = 6.4 oC

Cp = 4.18 J / g oC

qrxn = m Cp dT

        = 50 x 4.18 x 6.4

        = 1338 J

qrxn   = 1338 J     (or) 1.34 kJ