3. All of Physical Chemistry

Do you include a sign for the enthalpy change when drawing an energy level diagram?

No

Give two reasons why the student’s value is less exothermic than the data book value

Incomplete combustion is less exothermic than complete combustion
Not all the heat energy released is transferred to the water, some energy is transferred to the surroundings

Some N2O4 and some NO2 are put into a sealed gas syringe and allowed to form an equilibrium mixture. The equilibrium mixture is brown: then, the pressure is increase by pushing in the piston so that the new equilibrium mixture contains less NO2 (NO2 is a brown gas).

Suggest why the new equilibrium mixture is actually darker than the original

Amount of NO2 decreases and the volume decreases. concentration = moles/volume, so the concentration of NO2 increases

Explain why sulfuric acid is not a suitable acid to use in investigating the rate of reaction between marble chips and dilute HCl.

Would form a layer of insoluble CaSO4 on the surface of the marble chips, slowing the reaction

Explain why the use of a catalyst has no effect on the position of equilibrium in a reversible reaction.

The catalyst increases the rate of both the forward and reverse reactions equally