Which of the following would have a positive change in standard entropy at constant temperature? Choose all that apply.
A) Burning octane to form carbon dioxide gas and water vapor
B) Freezing titanium
C) The endothermic dissolving of ammonium nitrate solid in water
D) Sublimation of ice
A yes.
B no.
C probably yes. Wouldn't the entropy increase as the crystal lattice of NH4NO3 is broken and individual ions are floating around, even at a lower temperature?
D yes.
To determine which of the following options would have a positive change in standard entropy, we need to consider the factors that affect entropy.
Entropy is a measure of the degree of randomness or disorder in a system. Generally, the higher the randomness or disorder, the higher the entropy, and vice versa.
A) Burning octane to form carbon dioxide gas and water vapor:
Burning octane involves the conversion of a liquid hydrocarbon (octane) into gaseous products (carbon dioxide gas and water vapor). In this process, there is an increase in randomness or disorder as the liquid molecules are converted into gaseous molecules. Therefore, this reaction would have a positive change in standard entropy.
B) Freezing titanium:
Freezing is the process of converting a substance from a liquid or gas phase to a solid phase. During freezing, molecules lose their freedom of movement and become ordered in a regular crystalline structure. This reduction in randomness or disorder leads to a decrease in entropy. Therefore, freezing titanium would have a negative change in standard entropy.
C) The endothermic dissolving of ammonium nitrate solid in water:
Dissolving involves the separation of solute particles in a solid state and their distribution among the solvent (water) molecules. Dissolution increases disorder and randomness in the system, as the solute molecules become dispersed throughout the solvent. Therefore, the endothermic dissolving of ammonium nitrate in water would have a positive change in standard entropy.
D) Sublimation of ice:
Sublimation is the process in which a solid directly converts into a gas without passing through the liquid state. In the case of ice (solid water), sublimation represents an increase in randomness and disorder. The solid water molecules gain enough energy to break the intermolecular forces and become gaseous molecules, resulting in a positive change in standard entropy.
Therefore, the options that would have a positive change in standard entropy at constant temperature are:
A) Burning octane to form carbon dioxide gas and water vapor
C) The endothermic dissolving of ammonium nitrate in water
D) Sublimation of ice