Chapters 19-24 Flashcards
What is a spontaneous chemical reaction
One that will proceed to at least some extent without external assistance.
What are J. Willard Gibbs’s dates?
1839-1903
What is Gibbs free energy?
It gives us a way to combine enthalpy and entropy mathematically to determine whether the standard molar energy change for a process is positive or negative.
What does a positive free energy change mean for a reaction?
the reaction absorbs energy overall, so it is not going to take place without some outside assistance in the form of energy input. Non-spontaneous.
What does a negative free energy change mean for a reaction?
that the reaction releases energy to its surroundings and will happen all on its own, making it spontaneous.
What is the Gibbs free energy equation?
Delta G = Delta H - (T)*Delta S
What kind of process is occurring if the Gibbs free energy equation has a positive Delta H and a Negative Delta S?
It can never be spontaneous at or near standard conditions. Carbon turning into diamond, e.g.
What kind of process is occurring if the Gibbs free energy equation has a positive Delta H and a Positive Delta S?
we’ll have a reaction that is more spontaneous at higher temperatures. Melting of ice, e.g.
What kind of process is occurring if the Gibbs free energy equation has a negative Delta H and a Positive Delta S?
a reaction will always be spontaneous at or near
standard temperatures and pressures. Combustion of propane, e.g.
What kind of process is occurring if the Gibbs free energy equation has a negative Delta H and a negative Delta S?
we’d have to lower the temperature to make the reaction more likely to be spontaneous. In other words, it’s spontaneous at low temperatures. combustion of Hydrogen, e.g.
What are the 3 common phases of matter?
Solids, liquids and gases.
What are London dispersion forces?
temporary attractive forces that form when, just for an instant, the electron cloud of an atom or molecule becomes imbalanced.
How are London dispersion forces affected by the size of the atom?
as atoms and molecules become larger, and their electron clouds grow in size, interior electrons screen outer electrons from the nucleus, making them more susceptible to being pushed around from the outside of the atom.
What is a dipole‑dipole interaction?
For the same reason that transient dipoles align to form London forces, permanent dipoles can also align to form attractive relationships between and among molecules in a sample.
What are Hydrogen bonds?
intermittent but powerful attractions that take place between a very positively charged hydrogen and lone pair electrons from an atom carrying a very strong negative charge.
What are the three intermolecular forces?
London dispersion forces, dipole-dipole interaction and Hydrogen bonds.
Why is the density of ice only about 90% that of liquid water?
The lattice work of ice crystals formed by Hydrogen bonds, leaving more space.
What is a phase diagram?
a way to illustrate and demonstrate how and why a pure substance will change phases.
What is the triple point?
The unique set of conditions at which the solid, liquid and gaseous form of a substance can all exist in equilibrium.