Calculating Molar Heat of Solution for NaOH using a Calorimeter | Homework Help

  • Thread starter Christina-
  • Start date
  • Tags
    Heat
In summary, the question is asking for the molar heat of solution when 5.00 g of NaOH(s) is added to 100 g of water using a calorimeter. The temperature rises from 25.0 to 37.5 °C and the specific heat capacities of both water and NaOH(aq) are assumed to be 4.18 J/gK. Using the equations qp = Cp∆T and | Heat Lost | = | Heat Gained |, the molar heat of solution is calculated to be 93.214 kJ/mol. However, there may be a small mistake in the calculation of the heat gained by the water, which could affect the final answer.
  • #1
Christina-
11
0

Homework Statement


When 5.00 g of NaOH(s) are added to 100 g of water using a calorimeter (with Cp = 493.24 J/K), the temperature rises from 25.0 to 37.5 °C. Calculate the molar heat of solution.
[align=center]NaOH(s)--->Na(aq)+OH(aq)[/align]
Assume that the specific heat capacity of water is 4.18 J/gK and that of the NaOH(aq) solution is the same.

Homework Equations


1) qp = Cp∆T,
2) | Heat Lost by Hot Water | = | Heat Gained by Cold Water | + | Heat Gained By Calorimeter |

The Attempt at a Solution



Heat Gained By Solution:
(100 g H2O) x (4.18 J/gK) x (37.5 - 25)K = 5486.25 J

Heat Gained By Calorimeter:
Using qp = Cp∆T,
Cp∆T = (493.24 J/K) x (37.5 - 25)K = 6165.5 J


| Heat Lost | = 5486.25 J + 6165.5 J = 11 651.75 J = 11.65175 kJ

Molar mass of NaOH = (22.99 + 16.00 + 1.01) = 40
5.00 g NaOH x (1 mol ÷ 40g) = 0.125 mol

11.65175 kJ ÷ 0.125 mol = 93.214 kJ/mol



I was just wondering if I did that correctly. I don't actually know the correct answer, but one of my fellow students got a different answer and I'm unsure if I'm the one with the wrong answer or not.
If this isn't the way to find ∆H, could someone show me how or perhaps point me to a useful page on the internet?

Thanks
 
Physics news on Phys.org
  • #2
One small thing I can see immediately

you wrote;
(100 g H2O) x (4.18 J/gK) x (37.5 - 25)K = 5486.25 J
but this should actually be;
(100 g H2O) x (4.18 J/gK) x (37.5 - 25)K = 5225 J
or
(105 g H2O) x (4.18 J/gK) x (37.5 - 25)K = 5486.25 J

I don't know if this helps but it's what I could see immediately
 
  • #3
for your help!



Your calculations look correct to me. The molar heat of solution for NaOH using a calorimeter should be 93.214 kJ/mol. It's possible that your classmate made an error in their calculations. However, it's always good to double check your work and make sure you are using the correct equations and values. Additionally, it's always a good idea to compare your answer to a known value or do some research to see if your answer is within a reasonable range. Keep up the good work!
 

FAQ: Calculating Molar Heat of Solution for NaOH using a Calorimeter | Homework Help

What is the definition of molar heat of solution?

The molar heat of solution, also known as the enthalpy of solution, is the energy released or absorbed when one mole of a substance dissolves in a solvent to form a solution at constant pressure and temperature.

How is molar heat of solution calculated?

Molar heat of solution can be calculated by dividing the energy released or absorbed by the number of moles of the solute dissolved in the solution. This can be expressed in units of joules per mole (J/mol) or kilojoules per mole (kJ/mol).

What factors affect the molar heat of solution?

The molar heat of solution can be affected by factors such as temperature, pressure, and the nature of the solute and solvent. Generally, substances with stronger intermolecular forces will have a higher molar heat of solution.

What is an endothermic reaction in relation to molar heat of solution?

An endothermic reaction is one in which heat is absorbed from the surroundings, resulting in a decrease in temperature. In terms of molar heat of solution, this means that the solution process is taking in more energy than it is releasing, resulting in a positive value for the molar heat of solution.

How is molar heat of solution used in real-world applications?

Molar heat of solution is an important concept in fields such as chemistry, material science, and pharmaceuticals. It can be used to understand and predict the solubility of substances, as well as to design and optimize chemical reactions. It is also a crucial factor in the production of medications and the development of new drug formulations.

Back
Top