How to calculate the molar enthelpy

[supahsain]

Homework Statement

1) add 60 ml of 1.0 mol/L Sodium Hydroxide solution to a polystyrene calorimeter.
2) mix it with 40-ml sample of 1.0 mol/L sulfuric acid solution in a graduated cylinder.

3) Add the acid to the base, stirring slowly with the thermometer. record the highest temperature recorded

initial temp: 22.5
highest: 26

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Cacluate the number of moles of the base (the limiting reagent)

2) Calculate the change in molar enthalpy with respect to sodium hydroxide.

Homework Equations

The Attempt at a Solution

I think, I solved it. n = c.v
n = 0.06 * 1 = 0.06 mol NaOH


2nd) H = m.c.t/n

100g * 4.184 * 3.5 / 0.06
= 24.4 KJ
is this correct?

the reason why I am confused is because the accepted value is 56kj/mol. My answers is way off. Wither I messed up during the experiment or in my writtten solution or in both
Plz help

 

[Borek]

IMHO solution looks OK, so most likely there was something wrong with the experimental part.

 

[Blueshift5]

Your attempt at a solution appears to be mostly correct. However, there are a few things that could have contributed to your result being significantly different from the accepted value of 56 kJ/mol.

First, it is important to double check your experimental procedure and ensure that you measured and mixed the solutions accurately. Any small errors in measurement or mixing could significantly affect the final result.

Second, it is possible that there were some heat losses during the experiment, which could have affected the recorded temperatures and therefore the calculated change in molar enthalpy. It is important to take precautions to minimize heat losses during the experiment, such as insulating the calorimeter and stirring gently to avoid splashing.

Lastly, it is important to consider the assumptions and limitations of the calculation method you used. The formula H = m*c*t/n assumes that the reaction is the only source of heat and that the specific heat capacity (c) of the solution is constant. However, in reality, there may be other sources of heat and the specific heat capacity of the solution may change slightly as the temperature increases. This could also contribute to the difference in your result compared to the accepted value.

In conclusion, while your attempt at a solution appears to be correct, it is important to carefully review your experimental procedure and consider any potential sources of error or limitations in the calculation method. It is also helpful to compare your result with the accepted value and try to identify any discrepancies and possible reasons for them. This will help improve your understanding and accuracy in future experiments.