Question

How do you find heat of solvation of $N{H_4}Cl$?

Answer 1

Hint: We know that the enthalpy of solution is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure. In this question, we are asked to tell the manner in which the heat of solvation of ammonium chloride is measured experimentally. We must be quite familiar with terms like specific heat, calorimeter, endothermic etc. while answering this question.

Complete step-by-step answer:We will be needing thermometer, weighing balance, calorimeter, ammonium chloride, deionized water, stirrer
Step wise procedure for measuring heat of solvation of ammonium chloride is given as follows:
Measure the amount of solute i.e., ammonium chloride $N{H_4}Cl$ using a weighing balance.
Take a known volume of water. Now, using the density of water, we will now calculate the mass of water used as solvent.
Pour the given volume of water in the calorimeter. Using the thermometer, we will measure the initial temperature of the system.
Add that amount of solute i.e., ammonium chloride $N{H_4}Cl$ to the deionized water. Dissolve using a stirrer and now at this point, we will record the final temperature of the system using the thermometer.
In this experiment, ammonium chloride will absorb heat energy from the surrounding water and hence the temperature of the surrounding water will decrease.
Using the formula,
$Q = m \times s \times \Delta T$
Where m is the mass of water in units of g
s is the specific heat of water in units of $J\,{g^{ - 1}}^\circ {C^{ - 1}}$
Q is the heat lost by given amount of water in units of $J$
$\Delta T$is the change in temperature from initial to final temperature in units of $^\circ C$
But in the question, we are asked to find the enthalpy of solution of ammonium chloride.
We know that heat absorbed is always equal and opposite to heat released.
Hence, heat released on dissolution of ammonium chloride is equal to negative of Q.
Enthalpy change $ = Q\,gained\,by\,the\,salt \times moles\,of\,salt\,taken$
In units of $J\,mo{l^{ - 1}}\,or\,kJ\,mo{l^{ - 1}}$

Note: We now understand that Calorimetry has been used to calculate the enthalpy of solution of ammonium chloride.
We should note that the enthalpy change for solvation of ammonium chloride is an endothermic reaction. We should know about the specific heat capacity which is the heat needed to raise the temperature of one gram of a substance by one degree Celsius ($^\circ C$).