How do you find heat of solvation of #NH_4Cl#?
Enthalpy change for an aqueous solution can be determined experimentally. Utilizing a thermometer to measure the temperature change of the solution , (along with the mass of the solute) to determine the enthalpy change for an aqueous solution, as long as the reaction is carried out in a calorimeter or similar apparatus . You can use a coffee cup calorimeter.
Measure the mass of solute in grams using a balance. I am dissolving solute Ammonium chloride The mass I have taken is 5.4 g or 0.1 moles.
Measure the volume of water. I am going to use 100 ml of water. Record the Density of water. Using Density and volume of water I can calculate the mass of water using formula. Mass = Volume x Density (let us assume the density of water to be 1g / ml, the mass of 100 ml of water is 100g).
Pour the 100 ml of water in a coffee cup calorimeter, record the temperature of water , the initial temperature of water is
Add 5.4 g of Ammonium chloride to the water. Dissolve the Ammonium chloride using a stirrer and also record the temperature of solution. Let us assume that the final temperature of the solution is
In this dissolution experiment Ammonium chloride dissolves in water and absorbs heat energy from the surrounding water , which causes the temperature of water to go down from
#27^o#C to #19^o#C. The change in temperature is #19^o#C - #27^o#C = - #8^o#C
Use the formula Q = mass of water . specific heat of water . change in Temperature to calculate amount of heat gained by water.
Q = 100 g . 4.18 J /
#g^oC#. - #8^o#C
Q = -3344 J or -3.34 kJ
Water has lost -3.34 kJ of heat energy to the salt, or salt has gained + 3.34kJ of heat energy from water. So energy gained by salt is + 3.34 kJ.
Change in enthalpy = Q gained by salt / # of moles of salt
= +3.34 kJ / 0.1 mol = +33.4 kj /mol