Question

When 0.1002g o ammonium chloride is dissolved in 225mL of water in a constant pressure calorimeter, the temperature drops from 25.3 degrees celsius to 13.4 degrees celsius. What is the heat absorbed or released per gram and per mole of ammonium chloride.

Answer 1

A.**********Measure the mass of solute in grams using a balance. I am dissolving solute Ammonium chloride The mass I have taken is 0.1002 g or 0.0187 moles.

B.*********Measure the volume of water.we are going to use 250 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 1 g / ml, the mass of 225 ml of water is 225g).

C.********Pour the 225 ml of water in a coffee cup calorimeter, record the temperature of water , the initial temperature of water is 25.3⁰ C.

D.*********Add 0.1002 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 13.4 ⁰C

E.**********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 25.3⁰ C to 13.4⁰ C. The change in temperature is 13.4⁰ C - 25.3⁰ C = -11.9⁰C

F.***********Use the formula Q = mass of water . specific heat of water . change in Temperature to calculate amount of heat gained by water.

G.*********Q = 225 g . 4.18 J / g^oC. -11.9⁰ C

Q = -11191.95 J OR =-11.19195 KJ

Water has lost -11.191 95 kJ of heat energy to the salt, or salt has gained + 11.19195 kJ of heat energy from water. So energy gained by salt is + 11.19195 kJ.

ANS-1.Change in enthalpy = Q gained by salt / of moles of salt

= +11.19195 kJ / 0.0187 mol = +598.5 kj /mol

ANS-2.AND HEAT ABSORBED PER GRAM NH₄Cl = CHANGE IN ENTHALPY PER MOLE / MOLAR MASS OF NH₄Cl=+598.5/53.5 =+11.869Kj [ THANKS HOPE THIS WILL HELP YOU.GOOD LUCK]