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Chemistry Unit 1
Chapter 12 and 13
| Question | Answer |
|---|---|
| What is the Kinetic Molecular Theory? | it helps us interpret the properties of solids liquids and gases |
| KMT of solids | particles are closely packed together, usually in a regular array. the particles vibrate back and forth about their average position, but seldom does a particle in a solid squeeze past its immediate neighbors and contact with other particles |
| KMT of liquids | atoms or molecules of liquids are arranged randomly and are fluid-thus are able to move past each other. |
| KMT of gases | under normal conditions-particles of gases are far apart-they move extremely rapidly and collide with one another and the container walls-volume of a gas sample is the volume of the container since gases fill their container |
| what is the ideal gas law equation? | PV=nRT where P-atm, V-Liters, n-moles, R-.082057 latm/molk, and T-Kelvin |
| intermolecular forces get stronger as... | a substance changes from a gas to liquid to solid |
| Intermolecular forces are directly related to 3 things: | 1. properties such as melting point and boiling point, energy to convert between phases 2. determining the solubility of gases, liquids, and solids 3. determining the structure of biologically important molecules (DNA) |
| What is Coulomb's Law? | it states that the force of attraction between two charged objects depends on the product of their charges divided by distance(squared). |
| Explain an ion-dipole force | force of attraction between a negative or positive ion and a polar molecule-its force is less than an ion-ion force |
| when a polar molecule and an ion interact their forces depend on 3 factors | distance between ion and dipole (closer=>stronger) charge of the ion (higher charge=>stronger) magnitude of dipole (greater mag=>stronger) |
| what is an important example of the interaction between an ion and dipole molecule? | the formation of hydrated ions in aqueous solutions |
| what is the enthalpy change associated with the hydration of ions? | enthalpy of solvation |
| what is the enthalpy change associated with ions in water already? | enthalpy of hydration |
| dipole-dipole attraction | positive end of polar molecule is attracted to the negative end of another polar molecule |
| what do dipole-dipole attractions influence? | the evaporation of a liquid and the condensation of a gas among other things |
| evaporation is | endothermic-it requires INPUT of energy so it has a POSITIVE sign for enthalpy of vaporization |
| condensation is | exothermic-the reverse of evaporation and has a NEGATIVE value of enthalpy |
| the _________ the force of attraction, the ________ the energy needed to separate molecules in a liquid | greater, greater |
| for molecules of similar mass, the __________ the polarity, the _________ the boiling point-needed for molecules to escape the intermolecular forces of a liquid | the GREATER the polarity, the HIGHER the boiling point... |
| intermolecular forces influence | solubility -like dissolves like |
| boiling points _________ with molar mass | b.p.s INCREASE with higher molar masses |
| the ________ the difference in electronegativity, the __________ polar the bond | larger the difference between to atoms in electronegativity, the more polar the bond |
| hydrogen bonds MOST often include: | N, O, and F atoms |
| define hydrogen bond | an extreme form of dipole-dipole forces where one atom involved is ALWAYS hydrogen, H ( and n, o , f) |
| what is a dipole-induced dipole force? | it involves a dipole/polar molecule and a molecule that is induced to a dipole |
| what is the process of inducing a dipole? | POLARIZATION |
| define polarizability | the degree to which the electron cloud of an atom or a molecule can be distorted to a dipole |
| the _________ the molar mass, the __________ the polarizability of the molecule | the HIGHER the molar mass, the GREATER the polarizability |
| induced dipole- induced dipole force | the intermolecular force of attraction in liquids and solids composed of nonpolar molecules |
| London dispersion forces are otherwise known as... | induced dipole-induced dipole forces |
| london dispersion forces... | arise between all molecules and are the only intermolecular forces that allow NONpolar molecules to interact |
| Name the intermolecular forces from strongest to weakest... | ion-ion> ion-dipole> dipole-dipole> hydrogen> dipole-induced dipole> induced dipole-induced dipole |
| define vaporization | aka evaporation- the process in which a substance in the liquid state becomes a gas |
| vaporization is | endothermic because energy must be added to the system to overcome intermolecular forces of attraction |
| energy required to vaporize a substance is given as | the standard molar enthalpy of vaporization (in kilojoules/mole |
| define condensation | the reverse of vaporization, gas molecules lose sufficient energy when it contacts a liquid so it may reenter the liquid phase |
| condensation is | exothermic and so is the opposite of vaporization. the enthalpy of vaporization is negative instead of positive |
| the boiling points of nonpolar liquids ________ with __________ atomic or molecular mass | the b.p.s increase with increasing mass |
| what is dynamic equilibrium? | molecules move continuously from the liquid phase and vapor phase equally |
| the equilibrium vapor pressure is? | the pressure exerted by the vapor in equilibrium with the liquid phase-or the measure of the tendency of its molecules to escape from the liquid phase and enter the vapor phase at a given temp |
| define volatility | the tendency of its molecules to escape from the liquid phase and enter the vapor phase |
| the __________ the equilibrium vapor pressure, the ________ volatile the substance | the HIGHER the v.p., the MORE volatile the substance |
| all point along the vapor pressure versus temp curves represent conditions of... | pressure and temp at which liquid and vapor are in equilibrium |
| The Clausius-Clapeyron equation explains that...ln P = | -(enthalpy of vaporization/RT) + C R=8.314472 j/kmol |
| and ln P2/P1= | -(enthalpy of vap/R) * (1/T2-1/T1) t-kelvin, P-mmHg R=8.314472 j/kmol |
| Normal boiling point is found at | 760 mmHg!!!! |
| when a specific temperature and pressure are reached, the interface between liquid and vapor disappears. | Critical point with a critical temp Tc and critical Pressure Pc |
| if a substance exists under critical conditions it is called | a supercritical fluid |
| supercritical fluid is like | is like a gas under such a high pressure that its density resembles that of a liquid while its viscosity remains close to that of a gas |
| what is an example of a common supercritical fluid? | CO2- as a supercritical fluid can extract caffeine from coffee beans thus making the coffee decaf |
| surface tension | energy required to break through the surface of a liquid |
| capillary action | closely related to surface tension that involves adhesive forces(force between liquid and container) and cohesive forces (force between molecules) |
| define viscosity | the resistance of liquids to flow -longer chains of molecules have GREATER intermolecular forces |
| Name the types of solids | 1. ionic 2. metallic 3. molecular 4. network 5. amorphous |
| define unit cell | smallest repeating unit that has all the characteristics of the way the atoms, ions, or molecules are arranged in the solid |
| define lattice points | corners of the cube or geometric object that constitutes the unit cell |
| define crystal lattice | the assemblage of these three-dimensional unit cells |
| how many crystal lattices are there? | seven |
| cubic unit cell | simplest of seven crystal lattices, it is a cell with edges of equal length that meet at 90 degree angles |
| name the three symmetries of cubic unit cells | 1. Primitive cubic 2. body-centered cubic 3. face-centered cubic |
| alkali metals are | body-centered cubic in the solid state |
| Nickel, Copper, and Aluminum are | face-centered cubic |
| Polonium | primitive cubic |
| Primitive cubic | arrangement that has ONE net atom within the unit cell 8 corners*1/8 of each atom in each corner= 1 net atom per unit cell |
| Body-Centered cubic | arrangement that has a net of TWO atoms within the unit cell 8 corners*1/8 of an atom in each corner =1 atom + 1 atom in the middle of the unit cell |
| face-centered cubic | arrangement that has a net of four atoms within the unit cell 6 faces*1/2 atom within a unit cell= 3 net face-centered atoms + 1 atom from the 8 corners of the cell |
| how to find the radius of an atom in a unit cell | 1. calculate the mass of the unit cell itself - mass of one atom=> g/atom -g/atom times amount of atoms 2. calculate the volume of the unit cell -g/cell unit times cm(cubed) 3. calculate the edge of the unit cell -cube root 4. calculate the atom ra |
| ionic solids | primitive cubic or face-centered cubic with ions of opposite charge in the holes of the lattice |
| octahedral holes | example: NaCl- each Na+ is surrounded by 6 Cl- ions |
| face-centered cubic unit cell | ions not in octahedral holes... rather they are in tetrahedral holes |
| tetrahedral holes | each ion is surrounded by 4 oppositely charged ions |
| crystal structure | 1. Mn+ occupying all holes of primitive cubic Xn- lattice 2. Mn+ ions in octahedral holes of face-centered Xn- lattice 3. Mn+ ions in half the tetrahedral holes in fcc lattice Xn- ions |
| Ionic compounds have | high melting points which indicate strong bonds and lattice energy |
| ionic compounds exist as _________ under normal conditions | SOLIDS |
| Lattice energy | -measure of the strength of ionic bonding -energy of formation of one mole of a solid crystalline ionic compound when ions in the gas phase combine |
| U ion pair= | C*(Avogadro's number)*(n+e*n-e/d) c= constant d= distance between ion centers n+= # of positive cations n-= # of negative anions avogadro's number= 6.0221415 × 10^23 |
| lattice enthalpy | similar to lattice energy |
| ________ the ion charges, the _________ the attraction between opposite charges | Higher the ion charges, greater the attraction |
| Lattice enthalpy has a _____ negative value for ______-chargerd ions | has a larger negative value for higher-charged ions |
| attraction between ions is __________ to the distance between them | INVERSELY PROPORTIONAL |
| Born-Haber cylce | lattice enthalpies are calculated using a thermodynamic relationship an application of Hess' Law |
| steps of Born-Haber cycle | 1a. enthalpy of formation of ion 1b. lattice enthalpy for ion 2a. enthalpy of formation for ion 2b. lattice enthalpy for ion -combine all to find step 3- the total lattice enthalpy |
| Molecular solids | arrangement depends on the shape of molecules and intermolecular forces (discussed in ch. 12) |
| Network Solids | composed of 3-dimensional array of covalently bonded atoms |
| pure-crystalline solid properties | melt at a specific temperature, form well defined crystals with smooth, flat surfaces |
| amorphous solids | at a particulate level, these is no regular structure |
| properties of ionic solids | Hard, brittle, HIGH melting points, poor electronic conductivity as a solid, water-soluble |
| properties of metallic solids | Malleable, ductile, good electronic conductivity, good heat conductivity, wide range of hardness and melting points |
| properties of molecular solids | low to moderate melting points and boiling points, soft, poor electric conductivity |
| properties of network solids | wide range of hardness and melting points (3D bond> 2D bond), poor electric conductivity-with some exceptions |
| properties of amorphous solids | non-crystalline, wide range of melting points, poor electric conductivity-with some exceptions |
| Melting point | temperature at which the solid lattice collapses and the solid is converted to a liquid |
| energy of melting | enthalpy of fusion kJ/mol |
| energy of freezing | enthalpy of crystallization =negative enthalpy of fusion kJ/mol |
| ______ melting temperature means _______ enthalpy of fusion | Low melting temp means LOW enthalpy of fusion |
| melting point ___________ as size and molar mass ___________ | m.p. INCREASES as size and mass INCREASES |
| solid to gas | sublimation the opposite is deposition |
| sublimation is | endothermic enthalpy of sublimation |
| Phase diagram | used to illustrate the relationship between phases of matter and the pressure and temperature associated with it |
| the boundary lines show | equilibrium condition |
| define triple point | on the phase diagram that indicated conditions under which all 3 phases coexist at equilibrium |
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