How to determine the nthalpy of reaction of 0.1 M copper sulfate and with 1 M et

Question

How to determine the nthalpy of reaction of 0.1 M copper sulfate and with 1 M ethylene diamine in aqueous solution?

For lab I used a calorimeter to measure temperature change in the reaction of copper(II)sulfate (pentahydrate) solution with a diluted ethylenediamine solution. The two solutions were mixed in a styrofoam cup.

Preparation:

A 14.8 M ethylenediamine solution was diluted to 1M ethylenediamine. 67.7 mL of originial ethylenediamine solution was transferred to a 1000mL volumetric flask and diluted to the mark with deionized water. My teacher said to assume 0.1M copper sulfate for every 1M ethylenediamine (EDA) in the reaction.

1CuSO4 + 2EDA--> 1CuEDA2

Results: Measurements were taken 6 times for error calculation. But results for my first measurment were: added volume of copper sulfate was 50mL, added volume of ethylene diamine is 10 mL, initial temp was 21.2 celcius, final temp was 23.08 celcius, temp change was 1.96 celcius.

How would i go about finding the enthalpy of the reaction for my first measurement?

Explanation / Answer

H = Q/ n

where n is the number of moles of the limiting reagent

As per your reaction you need 1 mole of Copper solution and 2 moles of EDA since you have taken the right ratio you can take any one as the limiting reagent, remember that the final compound is 1 mole only so in both cases either using Copper moles or EDA modes the final is 1 mole even though you are using 2 moles of EDA it gives 1 mole of the final complex.

50 mL of 0.1M copper sulphate is 50 x 0.1/1000 =

Heat evolved or absorbed Q = m s T

where m = mass since we are in water solution we will use volume to equal mass as density of the water solutions can be approximated to 1

s is specific heat and again in water solution So for water , the specific heat is 4.18 J g-1 K-1.

T = temperature change

Q = (50+10) g x 4.18 J g-1 K-1 x 1.96 K= -491.6 J you can see that the unit also account for Joules as the final unit. The -ve sign indicates heat is evolved

( temperature unit has been put as K as it is a difference between 2 temperature and will remain same in K or C)

H = Q/ n = -491.6 J/0.005 = -98.32 kJ/mol

Hope this helps

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