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Chemistry 1200: Preparation for Second exam next Monday 25 of october
The following table cross-references similar material in the two texts that we use:
To read about the subject below Read here for Moore Read here for Kelter
Equilibrium Chapter 14 Chapter 16
Solvents and Solutions Chapter 15
Acids and Bases 16 17
Please review the DyKnow files!
There are several additional resources available. For instance, in BlackBoard, for each chapter, go to
Course Documents. Under Course Documents you will find another folder labeled PowerPoint and other
Chapter-by-Chapter resources. Under that folder you will find chapter by chapter material, each folder of which contains two important folders ( Chapter Terms and Definitions and Summary of Chapter Topics). You need to pay attention to the material in both those folders. Here’s what you need to pay attention to out of that material:
BlackBoard Source Comments
Course Documents
Chapter Terms and Definitions Chapter15 : You should familiarize yourself with all these terms. These are basic concepts upon which the course will be developed, so it is worth your time to get these right. Chapter 16: Again, these are all basic terms that you should be familiar with, especially LeChatelier’s principle Chapter 17 All terms
Course Documents
Summary of Chapter Topics Chapter 15 : Read through this material and the accompanying examples. Chapter 16 : Chapter 16 can be a challenging chapter if you allow yourself to be intimidated by mathematical equations. If you’ll just keep in mind what makes sense according to what you know to be true, you should be able to keep the numbers in their rightful place. You need to know more about the practical aspects of this chapter than being able to do arcane problems. On the other hand, you should know why specific equations are used for specific examples. Remember, in doing ANY math problems in chemistry, DO NOT FORGET TO WRITE DOWN THE UNITS THAT GO WITH THE PROBLEM. If you keep your units, the problem is self-correcting. If you leave the units out, I can almost guarantee that you will not do well. Chapter 17: This material has plenty of examples of how to do some of the acid/base equilibria problems.
Here is some more guidance with respect to what skills you are expected to acquire:
Know how to determine whether a chemical reaction has reached equilibrium (the concentrations of the
reactants and products remain constant over time).
Recognize the difference between static equililbrium and dynamic equilibrium.
The progress of chemical reactions is often depicted by a graph that shows the concentration of one or
more reactants and/or products as a function of time, such as in the following graph
Since the rate of a chemical reaction is defined as the change in molar concentration per unit time, the
rate of a chemical reaction is easily obtained by taking the slope of the concentration vs. time curve. Note
that for PRODUCTS you will always see an initial positive slope (the change in concentration per unit
time is greater than zero), while the slope for REACTANTS is always initially negative (you are
decreasing the concentration of reactants over time). As the reaction proceeds, both slopes will tend to
zero as you either reach equilibrium (as in the graph above) or you completely consume the reactants in a
non-reversible reaction. Be able to distinguish whether a given concentration vs. time curve shows a
reversible or irreversible reaction. The above curve shows an equilibrium. How do I know that? Read
your book. What would the curve look like if the reaction were not reversible but only ran in the forward
direction?
Pay special attention to being able to solve problems like Example 15.1 in Summary of Chapter Topics on
BlackBoard).. This type of problem will continue to show up in the chapters on Acids and Bases.
Chemical Equilibrium
Predict solubility based on properties of solute and sovent
Differentiate among unsaturated, saturated, and supersaturated solutions
Predict the effects of temperature and pressure on the solubility of gases in liquids
Describe the compositions of solutions in terms of weight percent, mass fraction, parts per million,
parts per billion, parts per trillion, molarity, and molality
Interpret vapor pressure lowering in terms of Raoult’s law
Use molality to calculate the colligative properties: freezing point lowering and boiling point
elevation
Differentiate the colligaive properties of nonelectrolytes and electrolytes
Past skills that need work:
Acids and Bases
Chemistry of Solutes and Solutions
Concentration calculations. Example problem: How many grams of NaCl are necessary to make up 500 mL of 0.5 M NaCl?
Know what the conjugate acid/base pair concept is all about
Be able to calculate the pH, pOH, concentration of H+^ and OH-^ in solutions of strong acid or base.
Know about the self-ionization of water, and that in ANY aqueous solution, the ionzation constant for
water, Kw, (i.e., the product of the concentrations of H+ and OH- ions)will ALWAYS be 1 x 10-
Example question: calculate the concentration of OH-^ ion in 0.10 M HCl.
(ANS=1 x 10-13^ M.)
Be able to calculate the pH and pOH from the hydrogen-ion concentration (or hydroxide ion
concentration), and vice versa.
Sample question: An ammonia solution has a hydroxide-ion concentration of 1.9 x 10 -^^3 M. What is the
pH of the solution?
(ANS=11.3)
heat of phase transition heat energy added to a substance during a phase change without any change in temperature of the substance (11.2) heat (or enthalpy) of fusion (ΔHfus) Hfus) enthalpy change for the melting of a solid (11.2) heat (or enthalpy) of vaporization (ΔHfus) Hvap) enthalpy change for the vaporization of a liquid (11.2) phase diagram graph that summarizes the conditions under which the different states of a substance are stable (11.3) triple point point on a phase diagram representing the temperature and pressure at which three phases of a substance coexist in equilibrium (11.3) critical temperature temperature above which the liquid state of a substance no longer exists regardless of the pressure (11.3) critical pressure vapor pressure at the critical temperature (11.3) critical point on a phase diagram, the point where the vapor-pressure curve ends and at which the temperature and pressure have their critical values (11.3) surface tension energy required to increase the surface area of a liquid by a unit amount (11.4) capillary rise rise of a column of liquid in an upright, small- diameter tube because of surface tension (11.4) meniscus curved upper surface of a liquid in a container (11.4) viscosity resistance to flow that is exhibited by all liquids and gases (11.4) intermolecular forces interactive forces between molecules (11.5) molecular beam group of molecules caused to travel together in the same direction; when two beams collide, the resulting data can be used to calculate the energy of molecular interactions (11.5, marginal note) van der Waals forces weak attractive forces between molecules, including dipole—dipole and London forces (11.5) dipole—dipole force attractive intermolecular force resulting from the tendency of polar molecules to align themselves such that the positive end of one molecule is near the negative end of another (11.5) instantaneous dipoles small partial charges on molecules due to momentary shifts in the distributions of electrons as they move about atomic nuclei (11.5) London (dispersion) forces weak attractive forces between molecules resulting from the small, instantaneous dipoles that occur because of the varying positions of the electrons during their motion about nuclei (11.5)
hydrogen bonding weak to moderate attractive force between a hydrogen atom covalently bonded to a very electronegative atom, particularly nitrogen, oxygen, or fluorine, and the lone pair of electrons of another small, electronegative atom (usually on another molecule) (11.5) molecular solid solid that consists of atoms or molecules held together by intermolecular forces (11.6) metallic solid solid that consists of positive cores of atoms held together by the surrounding "sea" of electrons (metallic bonding) (11.6) ionic solid solid that consists of cations and anions held together by electrical attraction of opposite charges (ionic bonds) (11.6) covalent network solid solid that consists of atoms held together in large networks or chains by covalent bonds (11.6) malleable able to be shaped by hammering, as are metallic crystals (11.6) crystalline solid solid composed of one or more crystals in which each crystal has a well-defined, ordered structure in three dimensions (11.7) amorphous solid solid that has a disordered structure; it lacks the well-defined arrangement of basic units (atoms, molecules, or ions) found in a crystal (11.7) polymorphic describes a substance that can crystallize in more than one crystal structure (11.8) in phase said of two waves of the same wavelength that come together so that their peaks (maxima) and troughs (minima) match (11.10) constructive interference result of combining two waves that are of the same wavelength and in phase such that the intensity of the resulting ray is increased (11.10) amplitude height of a wave (11.10) out of phase said of two waves of the same wavelength that come together with their peaks at opposite points and their troughs at opposite points (11.10) destructive interference result of combining two waves that are of the same wavelength and out of phase such that the intensity of the resulting ray is decreased or reduced to zero (11.10) Bragg equation equation relating the wavelength of x rays, λ, to the distance between atomic planes, d, and the angle of reflection, θ; nλ = 2d sin θ, n = 1, 2, 3, … (Instrumental Methods: Automated X-Ray Diffractometry) hydrologic cycle natural cycle of water from the oceans to freshwater sources and back to the oceans (A Chemist Looks at: Water [a Special Substance for Planet Earth])
lattice energy energy holding ions together in a crystal lattice (12.2) heat of solution heat that is released or absorbed when a substance dissolves in a solvent (12.3) Le Chatelier’s principle when a system in equilibrium is altered by a change of temperature, pressure, or concentration variable, the system shifts in equilibrium composition in a way that tends to counteract this change of variable (12.3) Henry’s law the solubility of a gas is directly proportional to the partial pressure of the gas above the solution; S = kHP (12.3) colligative properties properties of solutions that depend on the concentration of solute particles (molecules or ions) in solution but not on the chemical identity of the solute (12.4, introductory section) concentration amount of solute dissolved in a given quantity of solvent or solution (12.4) molarity (M) number of moles of solute per liter of solution (12.4) mass percentage of solute percentage by mass of solute contained in a solution (12.4) molality (m) number of moles of solute per kilogram of solvent (12.4) mole fraction (X) number of moles of a substance divided by the total number of moles of solution (12.4) mole percent mole fraction times 100 (12.4) vapor-pressure lowering colligative property of a solution; equal to the vapor pressure of the pure solvent minus the vapor pressure of the solution (12.5) Raoult’s law the partial pressure of solvent PA over a solution is equal to the vapor pressure of the pure solvent multiplied by the mole fraction of solvent in the solution: PA XA (12.5) ideal solution solution in which both substances follow Raoult’s law for all values of mole fractions (12.5) normal (boiling point of a liquid) temperature at which the vapor pressure of the liquid equals 1 atm (12.6) boiling-point elevation (ΔHfus) Tb) colligative property of a solution; equal to the boiling point of the solution minus the boiling point of the pure solvent (12.6) boiling-point-elevation constant (Kb) proportionality constant between the boiling- point elevation and the molality of a solution (12.6) freezing-point depression (ΔHfus) Tf) colligative property of a solution; equal to the freezing point of the pure solvent minus the freezing point of the solution (12.6) freezing-point-depression constant (Kf) proportionality constant between the freezing-point lowering and the molality of a solution (12.6) semipermeable describes a membrane that allows solvent
molecules, but not solute molecules, to pass through (12.7) osmosis phenomenon of solvent flow through a semipermeable membrane from lower solute concentration to higher concentration to equalize concentrations on both sides of the membrane (12.7) osmotic pressure colligative property of a solution; equal to the pressure that, when applied to the solution, just stops osmosis (12.7)
propane (^) butane Except for the first four members of the family, the name is simply derived from the Greek (or Latin) prefix for the particular number of carbon atoms in the alkane; thus PENTane for five, HEXane for six, HEPtane for seven, OCTane for eight, NONane for nine, DECane for ten and so on. You should certainly know the first ten. The structures drawn above are called "normal" alkanes because they form in a straight line without side chains. These, as well as others, form the base of a multitude of organic compounds. From these normal alkanes, we derive the names of certain groups that constantly appear as structural units of organic molecules. For instance, chloromethane, CH 3 Cl, is also known as methyl chloride. The CH 3 - group is called "methyl" wherever it appears. CH 3 Br is thus called methyl bromide, CH 3 I is called methyl iodide, and CH 3 OH is called methyl alcohol. In the same way, the C 2 H 5 group is "ethyl"; C 3 H 7 - is propyl; C 4 H 9 is butyl, and so on. The... means that something is attached at that point. Remember that carbon forms 4 bonds and hydrogen forms 1 bond, so when you see, for instance, C 4 H 9 - , it must for instance, have a structure of: With these things in mind, we will begin to name and draw structures for compounds using the system devised by IUPAC (International Union of Pure and Applied Chemistry). The rules devised by IUPAC for the alkanes are as follows:
- Select as the parent structure the longest continuous chain, and then consider the compound to have been derived from this structure by the replacement of hydrogen by various alkyl groups.
2. Where necessary, as in the isomeric methyl pentanes, indicate by a number the carbon to which
the branching alkyl group is attached. In numbering the parent carbon chain, start at whichever
end results in the use of the lowest numbers; thus the naming of the following isomers:
2-methylpentane 3-methylpentane Now, you might be wondering why there is no 1-methylpentane...
If you analyze the structure closely, you see that the added methyl group actually creates a longest chain that is now 6 carbon atoms in length. Thus, the structure above is correctly named hexane.
- If the alkyl group appears more than once as a side chain, indicate this by the prefix di-, tri-, tetra-, etc. These prefixes are used to show how many of these alkyl groups there are, and indicate by various numbers the positions of each group as shown below. 2,2,4-trimethylpentane
- If there are several different alkyl groups attached to the parent chain, name them in alphabetical order. The ethyl group is named before the methyl group because " e " (as in ethyl) comes alphabetically before " m " (as in methyl). The prefix does not contribute to the alphabetical order of the functional groups. 4-ethyl-1,4-dimethylheptane
- The prefix " iso -" is used to designate any alkyl group (of six carbons or less) that has a single one-carbon branch on the next-to-last carbon of a chain and has the point of attachment at the opposite end of the chain. isopropyl group isopropyl alcohol Isopropyl alcohol could also be (correctly) named 2-propanol, denoting the presence of the alcohol functional group (OH-) attached to the second carbon in the 3-carbon propane chain.
Rules for Naming Alkenes
- Select as the parent structure the longest continuous chain that contains the carbon-carbon double bond; then consider the compound to have been derived from this structure by replacement of hydrogen by various alkyl groups. The parent structure is known as ethane, propene, butene, pentene, and so on, depending upon the number of carbon atoms. each name is derived by changing the ending " -ane " of the corresponding alkane name to " -ene ". propene
2. If the parent chain is longer than three carbons, indicate by a number the position of the double
bond in the parent chain. Although the double bond involves two carbon atoms designate its
position by the number of the first doubly-bonded carbon encountered when numbering from the
end of the chain nearest the double bond.
1-butene 2-butene
3. Indicate by numbers the positions of the alkyl groups attached to the parent chain.
3,3-dimethyl-1-butene 4-methyl-2-pentene
Rules for Naming Alkynes
The alkynes can also be named by the IUPAC system. The rules are exactly the same as for the naming of alkenes except that the ending " -yne " replaces " -ene ". The parent structure is the longest continuous chain that contains the triple bond, and the positions both of the substituents and of the triple bond are indicated by numbers. The triple bond is given the number of the first triply-bonded carbon encountered, starting from the end of the chain nearest the triple bond. 1-butyne 2-butyne (^) 4-methyl-2-pentyne
Substituted Hydrocarbons
Hydrocarbons that are substituted with groups other than the alkyl groups are named in the same way. Other groups that are often substituted are the halogens (bromo-, chloro-, iodo-) as well as nitro (-NO 2 ) and amine (-NH 2 ). 2-bromopropane 1-chloro-2-butene 2,4-dinitro-2-pentene
bromo-2-methyl-2-propene The following table contains a summary of functional groups that substitute in hydrocarbons: An alcohol An aldehyde An amine A carboxylic acid An ester An ether
