Ozone story Flashcards
What is electronegativity defined as?
The ability of an atom to attract the bonding electrons in a covalent bond towards itself.
How does electronegativity change across a period?
Atomic radius decreases and charge density increases so electronegativity INCREASES
How does electronegativity change down a group?
Shielding and atomic radius both increase so electronegativity DECREASES.
What is a permanent dipole?
If two atoms that are bonded have significantly different electronegativities, a polar bond forms. The more electronegative atom draws more of the electronegative charge towards itself producing a (delta) pos and neg region.
What are polar molecules?
Arise when there is an overall difference in polarity across the molecule.
eg. CO2 contains C=O bonds which are polar however the molecule is linear so the dipoles cancel out.
What is an instantaneous dipole-induced dipole?
The weakest type so takes a low amount of energy to break the bonds meaning a low boiling point. Arise by an uneven arrangement of electrons in one molecule, creating a dipole for a fraction of a second, this instantaneous dipole then influences the electron distribution of an neighboring molecule which induces a dipole.
What is a permanent dipole-permanent dipole?
Stronger intermolecular forces then id-id so takes a larger amount of energy to break the bonds causing a higher boiling point. They arise by a significant electronegativity difference being present in a bond, which creates a dipole. The permanent dipole interacts with a neighboring molecule that also has a permanent dipole.
What is hydrogen bonding?
The strongest type of intermolecular force so they require the largest amount of energy to break the bonds, meaning a very high boiling point. They arise between the lone pair of electrons on a small electronegative atom such as nitrogen, oxygen or fluorine and the hydrogen atom in a molecule. The electronegative atom has a slight electronegative charge, while the hydrogen atom has a slight positive charge. Dashed line represents the hydrogen bond.
What is activation energy?
The minimum energy required for a reaction to take place between two colliding particles.
How do chemical reactions occur?
When the reactant particles collide. For a reaction to occur successfully these collisions must have energy greater then or equal to the activation energy.
Effect of temperature on rate of reaction?
When a substance is heated, thermal energy is transferred to it which is then converted into kinetic energy and the molecules of the substance move faster and further. Collisions can occur more often and with more energy. Increasing temperature increases rate of reaction as there are more frequent successful collusions.
How does the addition of a a catalyst have an effect of rate of reaction?
A catalyst is a substance that increases the rate of reaction without being used up in the reaction. It works by providing an alternative path with a lower activation energy. They are used in the industry as they lower the energy costs of the activation process. They also give a higher atom economy thus being economically important. They increase the sustainability of a reaction by lowering temperatures and reducing the energy demand from combustion of fossil fuels which reduces carbon dioxide emissions.
What are homogenous catalysts?
Catalysts that are in the same physical state as the reactants and products.
Maxwell-Boltman distribution curve
-plot of the no of molecules against kinetic energy
-peak is the most probable energy and mean curve is to the right
-curve is asymptotic so does not reach the x axis as there is no max value for the kinetic energy of a molecule
-total area under the curve represents the number of molecules in the sample so this area must remain constant.
What is the effect of temperature on the Maxwell-Boltman distribution curve?
curve shifts to the right and down when the temperature is increased because a greater proportion of molecules have greater kinetic energy which means a greater proportion of molecules will have energy greater than or equal to the activation energy.
