Determine delta H

Question

In a coffee-cup calorimeter, 1 mol NaOH and 1 mol HCl initially at 22 oC (Celsius) are mixed in 100g of water to yield the following reaction:
NaOH + HCl → Na+(aq) + Cl-(aq) + H2O(l)

After mixing the temperature rises to 110.5 oC. Calculate the change in enthalpy of this reaction.

Specific heat of the solution = 4.184 J/(g oC)

State your answer in kJ with 3 significant figures. Don't forget to enter the unit behind the numerical answer.

The molecular weight of NaOH is 40.0 g/mol, and the molecular weight of HCl is 36.5 g/mol.

 

What is delta H? 

Answer 1

Hi Lara,

 

the combined mass of the solution is 40.0 g (NaOH) + 36.5 g (HCl) + 100 g (H2O) = 176.5 g solution

 

the formula to determine the total energy released upon neutralization is:

 

q = mass x specific heat x change in temperature

q = (176.5 g) x (4.184 J/gC) x (110.5 - 22 C) = 72.74 kJ

 

therefore, the total enthalpy of reaction is 72.74 kJ/mol because only one mole of reagent was used.

 

Sincerely,

 

Alex