General Chemistry ThermoChemistry

Question

When 3.02 g of NH₄Cl  is dissolved in enough water to make 20.05 mL of solution, the temperature dropped from 19.8°C to 9.1°C. Calculate the enthalpy change (in kJ) when 1 mole of NH₄Cl is dissolved in water. The density and specific heat of water are 1.00 g/mL and 4.18 J/g°C respectively.  

Answer 1

Energy taken in : Q = mcΔt

= 20.05 x 4.18 x 10.7

= 896.7563 J

no of moles of NH4Cl = 3.2/53.5 = 0.059

0.059 moles takes in893.756 J of energy

So 1 mole will give 15199.15J .

i.e 15.19kJ

Enthalpy change is 15.19kJ