The molar enthalpy of solution for ammonium chloride is +14.8 kJ/mol. What is the final temperature observed when 20.0g of a....

Question

The molar enthalpy of solution for ammonium chloride is +14.8 kJ/mol. What is the final temperature observed when 20.0g of ammonium chloride is added to 125 mL of water at 20.0°C ? Give only the quantity in °C. Don’t give the unit.

Answer 1

20.0 g NH4Cl x 1 mol NH4Cl/53.5 g = 0.3738 moles NH4Cl

0.3738 moles NH4Cl x 14.8 kJ/mol = 5.53 kJ of heat energy required

To find the change in temperature, we use q = mC∆T where

q = heat = 5.53 kJ = 5530 J

m = mass = 125 ml x 1g/ml = 125 g + 20 g = 145 g

C = specific heat of water = 4.18 J/gºC

∆T = change in temperature = ?

Solving for ∆T, we have...

∆T = q/(m)(C) = 5530 J / (145 g)(4.18 J/gºC)

∆T = 9.12