1. Calculate the amount of energy given off when 17 g of vapor at 102C condenses to 87C Did a phase change occur? If so, which one? Is this endothermic or exothermic?

- Amount of energy = -1066.92 J

- Yes, a phase change occurs from gaseous state to liquid state

- It is exothermic

Explanation:

Using Q = m × c × ∆T

Where Q = amount of energy

m = mass = 17g

c = specific heat capacity of water (4.184J/g°C)

∆T = change in temperature (87°C - 102°C = -15°C)

Hence, Q = m × c × ∆T

Q = 17 × 4.184 × (-15°C)

Q = -1066.92 J

- According to this question, vapor condenses i.e. gaseous form of water changes to liquid water, which involves a reduction in temperature. Hence, a change of phase occurs from gaseous state to liquid state.

- Since the change of phase occurs from a less orderly state (gas) to a more orderly state (liquid), there is a release of energy i.e. EXOTHERMIC. The amount of energy or Enthalpy change (∆H) is negative