Consider the following equation.
fe2o3(s) + 3h2(g) → 2fe(s) + 3h2o(g)
h = 98.8 kj, and s = 141.5 j/k. is this reaction spontaneous or nonspontaneous at high and low temperatures?
a. spontaneous at high temperatures, non-spontaneous at low temperatures
b. non-spontaneous at high and low temperatures
c. spontaneous at low temperatures, non-spontaneous at high temperatures
d. spontaneous at high and low temperatures

This reaction is A. Spontaneous at high temperatures, and non-spontaneous at low temperatures.

Explanation:

Both the enthalpy change and the entropy change due to this reaction are positive. A chemical reaction will be spontaneous only if the change in its Gibbs Free Energy is negative. is the absolute temperature in degrees Kelvins.

Assume that both and doesn't change much as increases. The value of will initially be close to when is small. The sign of will depends on that of . However, is positive, so at low temperatures will be positive and the reaction will be non-spontaneous.

However, as increases, the role of entropy change becomes more significant. The sign of will eventually be the opposite of . The value of will eventually drop below zero after the value of rises above . The reaction will eventually become spontaneous.

adding or remove a gaseous reactant or product changes the concentrations. if the concentration of reactant or product is increased, the system will shift away from the side in which concentration was increased (i.e. if the concentration of reactants is increased, the system will shift toward the products. if more products are added, the system will shift to form more reactants). conversely, if the concentration of reactant or product is decreased, the system will shift toward the side in which concentration was decreased (i.e. if reactants are removed, the system will shift to form more reactants. if the concentration of products is decreased, the equilibrium will shift toward the products).

explanation:

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.