Answer to Question #135775 in General Chemistry for janes

Question

A 2.10 mole sample of crystalline acetic acid, initially at 17.0°C, is allowed to melt at 17.0°C and is then heated to 118.1°C (its normal boiling point) at 1.00 atm. The sample is allowed to vaporize at 118.1°C and is then rapidly quenched to 17.0°C, so that it recrystallizes. Calculate DH° for the total process as described

Answer 1

2.10 mole sample of crystalline acetic acid

1) initially at 17.0°C, is allowed to melt at 17.0°C and

2) then heated to 118.1°C (its normal boiling point) at 1.00 atm. and sample is allowed to vaporize at 118.1°C

3) and then it rapidly quenched to 17.0°C, so that it recrystallizes to crystalline acetic acid.

So, initial state and final state ara identical.

As, the enthalpy, H is a state function, only change if final and initial state are different.

So, DH =0 for the total process described