The ΔH for the solution process when solid sodium hydroxide dissolves in water is 44.4 kJ/mol. When a 6.21-g sample of NaOH dissolves in 250.0 g of water in a coffee-cup calorimeter, the temperature increases from 23.0 °C to °C. Assume that the solution has the same specific heat as liquid water, i. e., 4.18 J/g-K.

The final temperature of the solution is 29.6°C

Explanation:

To calculate the number of moles, we use the equation:

Given mass of NaOH = 6.21 g

Molar mass of NaOH = 40 g/mol

Putting values in above equation, we get:

To calculate the enthalpy change of the reaction, we use the equation:

where,

q = amount of heat absorbed = ?

n = number of moles = 0.155 moles

= enthalpy change of the reaction = 44.4 kJ/mol = 44400 J/mol   (Conversion factor:  1 kJ = 1000 J)

Putting values in above equation, we get:

To calculate the heat absorbed by the calorimeter, we use the equation:

where,

q = heat absorbed = 6882 J

m = mass of water = 250 g

c = heat capacity of solution = 4.18 J/g.K = 4.18 J/g°C

= change in temperature =

Putting values in above equation, we get:

Hence, the final temperature of the solution is 29.6°C