Question

The complete oxidation of one mole of a sugar produces carbon dioxide and water. 2000 kJ of heat is transferred from the system to the surroundings. The rearrangement of bonds as 0.5 moles of the sugar are oxidized generates heat in an open test tube (101 J•L–1 pressure and 300 K temperature). What is the change in internal energy of the system (ΔU)? What is the change in enthalpy of the system(ΔH)?

Answer 1

Step-by-step explanation:

According to the first law of thermodynamics,

`\Delta U = q + w`

When there is no work done then, w = 0.

As, 0.5 mole of sugar generates heat (q) = -2000 kJ

So, amount of heat (q) generated by 1 mole of sugar will be calculated as follows.

`-2000 kJ * 0.5`

= -1000 kJ

So, putting the values into the above formula as follows.

`\Delta U = q + w`

= -1000 kJ + 0

= -1000 kJ

Also, according to the definition of enthalpy the relation between enthalpy and internal energy is as follows.

`\Delta H = \Delta U + P \Delta V`

As change in volume is 0.

Hence,
`\Delta H = \Delta U`

= -1000 kJ

Thus, we can conclude that the change in enthalpy of the system(
`\Delta H`) is -1000 kJ.