Question

When a 4.00-g sample of KSCN is dissolved in water in a calorimeter that has a total heat capacity of 2.930 kJ K-1 the temperature decreases by 0.340 K. Calculate the molar heat of solution of KSCN. Number k.J/mol seln

Answer 1

Heat change = heat capacity × change in temperature

Therefore; heat change=2.930×0.340=0.9962kJ

Mass of KSCN =97g

Number of moles of KSCN present in sample= Given mass/molecular mass = 4/97=0.041 mol.

So 0.041 mol absorbs 0.9962kJ of energy

Therefore 1 mol of KSCN absorbs= 0.9962/0.041=24.29kJ

Molar heat of solution of KSCN is heat absorbed by 1 mol.

Molar heat of KSCN=24.29kJ.

NOTE: heat change formula: ∆q=c∆T.where c is heat capacity.∆T is change in temperature.∆q is change in heat.