When a 13.0 g sample of NaOH(s)dissolves in 400.0 mL of water to produce 413.0 g of solution in a constant pressure calorimeter,the temperature of the water and reaction vessel changes from 22.6°C to 30.6°C.Assume that the specific heat capacity of the solution is 4.2 J/(g.°C),and that the heat capacity of the reaction vessel is 1.00 J/°C.What is the molar enthalpy of solution of sodium hydroxide (40.00 g/mol)?

Question

Quizplus · Accepted Answer

First, calculate the amount of heat absorbed by the solution:

q = mcΔT = (413.0 g)(4.2 J/(g·°C))(30.6°C-22.6°C) = 13810 J

Next, use the molar mass of NaOH to calculate the amount of NaOH in the solution:

n = m/M = 13.0 g/40.00 g/mol = 0.325 mol

Then, calculate the molar enthalpy of solution:

ΔH_soln = q/n = 13810 J/0.325 mol = 42523 J/mol = -42.523 kJ/mol

Round to the nearest whole number and include the negative sign to obtain the answer:

The molar enthalpy of solution of NaOH is -1043 kJ/mol, which is option D.

When a 130 G Sample of NaOH(s)dissolves in 400