At low temperatures mixtures of water and methane can form a hydrate, that is, a solid containing trapped methane. Hydrates have both positive and negative features. For example, they are potentially a very large source of underground trapped methane in the Arctic and Antarctic regions that could be used to meet future energy needs. However, in cold areas such as the North Slope of Alaska and in the North Sea, hydrates can form in pipelines, blocking the flow of natural gas. The approximate stoichiometry of hydrate formation is 

The equilibrium partial pressure of methane for hydrate formation at 267 K is approximately 2.0 MPa, and at 255 K it is 1.5 MPa. Using the fact that the standard states for this reaction are pure methane as a gas at 1 bar, and water and the hydrate as a pure solid: 

a. Find Δ_rxnG° for hydrate formation per mole of methane at 267 K and 255 K. 

b. Assuming that Δ_rxnH° and Δ_rxnS° are independent of temperature, calculate values for these quantities. 

c. Use the information in the problem statement to calculate the equilibrium methane partial pressure for hydrate formation at 273 K.

Transcribed Image Text:

CH4 (g) +5.75H₂O(s) → CH4-5.75H₂O(s)