Chapter 6 (Thermochemistry)

Question 1

Define work

Answer 1

Work = Force * distance = Pressure*ΔVolume

Question 2

Define pressure

Answer 2

Pressure = Force/area

Question 3

What does the sign mean for work (+/-)?

Answer 3

Positive = Work done on the system (compression)
Negative = Work done by the system (expansion)

Question 4

Define enthalpy

Answer 4

Total system heat/energy. Enthalpy is a state function, meaning we only care about the initial and final states.
Enthalpy (H) = Internal energy (U) + Pressure*Volume

Question 5

What is q?

Answer 5

Heat/Energy transfer. Unlike enthalpy, we can measure this directly using a bomb calorimeter.
q=mcΔT

Question 6

When would ΔH be negative?

Answer 6

Exothermic reactions; heat transferring to surroundings

Question 7

Define specific heat (c)

Answer 7

The amount of energy required to heat 1 gram of a substance by 1˚C

Question 8

Define Hess’s law and what it describes

Answer 8

Hess’s law allows us to calculate the enthalpy change for a specific reaction.
ΔHrxn = sum(ΔHproducts) - sum(ΔHreactants)

Question 9

Define standard enthalpy of formation

Answer 9

The enthalpy change of the formation of 1 mole of a compound from its elemental form. (Elemental forms have 0 enthalpy).