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Chemistry Review Section. Pages 3 to 33 “Quantum Chemistry” Target Completion Date: October 1. Pages with a PINK background are supplementary . Not material for a test!. About Slide Icons. Very Important Points
Pages 3 to 33
Target Completion Date: October 1
Pages with a PINK background are supplementary . Not material for a test!About Slide Icons
Very Important Points
Important Sample Problems
Look at this! (usually charts, diagrams or tables)
Information only. Don’t copy!
The table on the left gives the eight most commonly used prefixes in the metric system.
It also includes five rows that do not have prefixes.
The middle row is for the unit: metre, litre, gram, newton, or any other legal metric unit.
This table can be used to quickly convert from one metric amount to an equivalent. Make a copy of this table on the margin of the front cover of your notebook, and learn how to use it.
Lets do an example. Let’s find how many centimetres there are in 2.524 km
Conversion: 2.524 km ? cm
00 cm Add extra zeros if necessary
2 524 km
There are five steps in the table between “kilo” and “centi”, so we have to move the decimal five places to the right. If we were going up the table we would move left.
Answer: 2524 km = 252 400 cm
Where: ρ= the density of the object, in g/cm3 or g/mL
m = the mass of the object, in g
V = the volume of the object, in cm3 or mL
The density of water is 1 g/mL. This is not true of other substances. Objects with less density than water will float. Objects with greater density will sink.
ρw= 1 g/mL = 1 g/cm3
Problem: A block of material has a length of 12.0 cm, a width of 5.0 cm, and a height of 2.0 cm. Its mass is 50.0 g. Find its density.
Arrange your solution like this:
List all the information you find in the problem, complete with units, and the symbols.
l = 12 cm.
w = 5.0 cm
h =2.0 cm
V = ?
Write down all the formulas you intend to use:
Formulas: V = lwh
Show the substitutions you make, and enough of your calculations to justify your solution:
V =12cm x 5cm x 2 cm
= 120 cm3
𝜌= 50 g / 120 cm3
= 0.46 g/cm3
Always state your answer in a complete sentence, with appropriate units.
Answer: The density of the block is 0.46 g/cm3 (or 0.46 g/mL)
Also: Do the worksheets entitled “Density” and “Metric Conversions”
In the sciences, we have an particular way of determining how much precision we need in the observations and answers we record. The method of rounding is called significant digits or significant figures. There is a detailed section in the appendix to your textbook on pages 394 to 397. Unfortunately, a few of the details given there are, well… I won’t say wrong, let’s just call them “uncertain”.
In math, numbers are considered pure, abstract things. In math, 2.00, 2.0 and 2 are considered the same, they all represent perfect number 2.
In science, numbers are considered to be measurements, and all measurements have some degree of uncertainty. They are almost never considered perfect!
The absolute uncertainty of a measurement is usually ½ of a measuring instruments smallest gradation. If a graduated cylinder is marked in millilitres, then each measurement taken with that cylinder has a ±0.5 mL uncertainty.
In science, 2 mL, 2.0 mL and 2.00 mL are different!
Rule 1. Non-zero digits are ALWAYS significant.
1.234 has 4 significant digits
145 has 3 significant digits
19567.2 has 6 significant digits
Rule 2. Zeros between significant digits ARE significant.
5007.4 has 5 significant digits
20000.6 has 6 significant digits
Rule 3. Zeros at the beginning are NEVER significant.
007 has 1 significant digit
0.0000005 has 1 significant digit
0.025 has 2 significant digits
Rule 4. Zeros at the end of a number MAY be significant.
Your textbook says that they are ALWAYS significant, but this is contrary to what most textbooks say.
If there is a decimal point, there is no problem. All textbooks agree, the zeros are ALL significant.
3.00000 has 6 significant digits
5.10 has 3 significant digits
10.00 has 4 significant digits
If there is NO decimal, the situation is ambiguous, and a bit of a JUDGEMENT CALL. If you trust the source to be precise, then you count all the zeros at the end. If you have reason to believe the person was estimating, then you don’t count any of the zeros at the end.
5000 has 1 or 4 significant digits
250 has 2 or 3 significant figures
123 000 000 has 3 or 9 significant figures
In a test situation, assume the numbers are precise, unless something in the question states otherwise.
Trusted precise source
Rule 5: Exponents and their bases, perfect multiples, uncertainties (error values), signs etc. are NEVER significant.
6.02x 1023 has 3 significant digits
504.1 mL x 3has 4 significant digits
5.3±0.5 mL has 2 significant digits
–5.432x 10-5has 4 significant digits
In each case, the blue part is significant, the greenpart is NOT significant.
Note: The term Significance in this usage is not the same as importance. A digit may be “insignificant” but still very important. The significant digits guide you to the correct way of rounding numbers to show precision. The insignificant digits may serve as “placeholders”, making sure the decimal point is in the right place. An important job, but not one that adds to the precision of the answer.
Try to avoid the “ambiguous” situation in your answers. If an answer ends in zero, or worse, in several zeros, indicate whether it should be interpreted as “exactly” or “approximately”.
Better still, convert it to scientific notation, and leave only the zeros you know are accurate.
Eg. If your answer is 2500 mL, but you only measured to the nearest 10mL, then write 2.50 x 103 mL. That way every one will know its accurate to 3 significant figures
*Your textbook says to call this 3 significant figures. Traditional measurement would call it 1 significant figure. Written this way it is ambiguous.
Avoid writing answers that end with zeros and no decimal!
53.81 m x 2.43 m = 131 m2NOT130.7583 m2 !!!
Why? Because the least precise measurement had 3 significant digits, so our answer should not have more than 3 significant digits!
The technique for addition and subtraction is slightly different (see p.396 ) but the concept is the same. You cannot make your result better than your measurements!
RTopic 1: Organization of Matter
several thousand atoms
2 atoms of hydrogen
1 atom of oxygen
Notice the slightly stronger wording with respect to metals than nonmetals!
Metal Ions (+)
Non-Metal Ions (-)
Notice that some elements can form more than one type of ion. Compounds of the same element can differ quite a bit, for example, red iron oxide (rust) has Fe3+ ions, black iron oxide (wustite) contains Fe2+ ions. Note also, that most negative ions have the name ending changed to –ide.
OBig Fat Ions(Polyatomic Ions)
Na+ + NO3- NaNO3
This information is important when naming ternary ionic compounds. Click to skip ahead to Ionic Naming Rules
Original and Modern
1. Rutherford-Bohr Model
Early Rutherford model
Revised Bohr model
2. The Simplified Atomic Model
Symbol: The symbol of the element
Electrons: 2 in first shell, 8 in 2nd 1 in 3rd
The Atomic Number, Z, is the number of protons in the element. The configuration is the arrangement of the electrons in the shells
2e- 8e- 1e-
Nucleus: If asked for a complete simplified model, give the #protons and #neutrons (if known) in the nucleus. Otherwise, just draw a full circle.
Z=11, configuration: 2,8,1
Nucleus is not shown.
Nucleus is confused with 1st shell
Nucleus shown as solid circle.
Labelled with element symbol beside.
Nucleus shown as full circle.
Labelled with #protons and neutrons.
3. Lewis Model: (AKA Lewis electron dot notation)
2 paired electrons
3 “odd” unpaired electrons
The preferred way of drawing Lewis diagrams of the first ten elements is shown below:
However, the dots may be moved around to show different arrangements. All of the drawings of Beryllium shown below might be correct in some circumstances.
Sometimes electrons are removed from one atom to others in order to get 8
Sometimes showing the bonding between atoms requires clever movement of dots, as in the drawing of a nitrogen molecule (N2) shown here:
The periodic table is a useful arrangement of the elements, into regions, families and periods that have important meanings. It is also a source of much additional information about the elements. With careful interpretation of the table, we can find the number of protons an atom has, the approximate number of neutrons, and the arrangement of electrons in the atom and in its ions.
An average carbon atom weighs 12.01 amu according to the periodic table. But no atom of carbon has that exact weight. For every thousand atoms that weigh exactly 12 amu, a few weigh more. This one weighs 14 amu
Ionic Charge (4–)
Oxidation # (–4)
Isotope or Mass number. Represents the number of nucleons in a particular atom
Valence is the number of bonds the atom is likely to form. Ionic charge is the most likely charge an ion will have.
Atomic number “Z” represents the number of protons in this atom
Subtracting the Mass # and the Atomic # “Z” gives the number of neutrons in the atom
Number of atoms in a molecule, such as C2H4
(6p+, 8n0, 10e-)
Configuration of this atom
Atomic number (Z)
The number of protons
Density (g/L gas)
Melting Point (°C)
Boiling Point (°C)
Electronegativity is a rating of how well the atom attracts electrons, on a scale from 0 to 4
The English name of the element
Atomic weight (amu)
Ionization Energy is how much energy it takes to remove an electron (kj/mol)
Also the molar mass in g/mol
The symbol is a 1 or 2 letter abbreviation of the element’s name, or sometimes its Latin name. The first letter is always uppercase. If there is a second letter it MUST be written in lowercase. (eg. For sodium, Na is correct, na or NA are absolutely unacceptable!)
↑ The properties and region associations of these 10 elements are hypothetical ↑
The heavy “staircase” line was the traditional separation between metals & non-metals but we now know it is not a sharp division.
VIIIA: Noble Gases
IIA: Alkaline Earths
IA: Alkali Metals
VI: Oxygen Family
IVA: Carbon Family
IIIA: Boron Family
V: Nitrogen Family
IB: Coin Metals
↑ The properties and family associations of most elements in period 7 are hypothetical↑
↑ The properties and family associations of these synthetic elements are hypothetical ↑
If the square is the same colour as the arrow above, it obeys its family with respect to valence. If the square is rainbow shaded, it is polyvalent, and not obeying its family rules. If the square is partly shaded, then it obeys its family rules most of the time.
1st Period = 1 shells
2nd Period = 2 shells
3rd Period = 3 shells
4th Period = 4 shells
5th Period = 5 shells
6th Period = 6 shells
7th Period = 7 shells
↑ The properties and family associations of these 10 elements are hypothetical ↑
6th Period = 6 shells
7th Period = 7 shells
The periods of the table show how many shells of electrons an element normally has.
Eg. Find the electron arrangement of Iodine (I)
5th Period = 5 shells
Iodine is at the intersection of Period 5 and Family VII. Its number is 53. It has a total of five shells, 7 electrons in the outermost shell, and will have 53p+, and normally 53 e-. From this we can USUALLY figure out the electron arrangement.
Total 53, So far: 35, left: 18
NaCl sodium chloride BaCl2 barium chloride
CaO calcium oxide K2S potassium sulphide
Al2O3 aluminum oxide Ca2C calcium carbide
YOU SHOULD NOT USE A PREFIX!
There are, or rather there USED to be, a few exceptions to this. Chromium dioxide was an acceptable name for CrO2, and is still used occasionally. Now the name chromium(IV)oxide is preferred for the compound, since it obeys the ionic rules. Monosodium glutamate is an organic compound that does not follow the rules.
This copper ion has a charge of 1+
This copper ion must have a charge of 2+
*Ferrosso ferric oxide is a unique combination of Iron(II)oxide and Iron(III)oxide together in a crystalline ionic structure Its formula can also be given as (FeO∙Fe2O3)
Polyatomic ions: See Table 8.10 on p. 422
* The last “o” in mono or the “a” in tetra, penta, or hexais usually dropped before “oxide” to sound better. (eg. “Carbon monoxide”, not “carbon monooxide”)
** The “mono” prefix is usually dropped from the first element of the compound, except when that would cause confusion between two similar compounds.
One of the uses of electronegativity is to decide which element goes first in a formula or name. Usually the element with the lowest electronegativity goes first. Therefore it is called carbon dioxide (CO2), NOT dioxygen carbide (O2C).
There are a few exceptions, like CH4 and NH3, where the more electronegative elements are written first. These formulas have been used for years, and are based on organic chemistry concepts, so it’s unlikely we will change them.
*commonly called hydrogen peroxide.
Notes: 1) The compound “sulphur chloride” should properly be called sulphur dichloride
2) The prefixes trump the crossover rule. If any prefixes were used in the name, then they take precedence over whatever formula the crossover rule would give you.
Note: Do not simplify covalent compounds by cancellation. Covalent compound formulas must reflect the compound names that include prefixes.
There’s a problem here! Oxygen hardly ever has a valence of 1. Let’s double both valences.
Fe has a valence of 3, so the name of the compound is:
Fe’s proper valence here is 2
A system of names for organic compound exists that is based on the number of carbon atoms they have (as a prefix), and the type of compound they are (as a suffix): alkane (…ane), alkene (…ene) alcohol (…ol), aldehyde (…hyde), ketone (…tone), organic acids, etc.
As you may notice, the common names of some chemicals come from the organic system, such as methane, the common name of carbon tetrahydride (CH4) . For more information on organic nomenclature, see the wikipedia article.
NA =6.02 x 1023
= 602 000 000 000 000 000 000 000
= six hundred and two sextillion
M(CO2)=44.009 g/mol, (frequently rounded to 44.0 g/mol)
How to Remember the Diatomic Elements: IHave No Bright Or Clever Friends
# moles =
Molar mass =
Actual mass = # moles x molar mass
Picky note: What your textbook calls “phase change” should more properly be called “change of state”. Although “phase” and “state” are frequently used as synonyms, the word phase has a broader meaning in chemistry. There are three main states of matter (solid, liquid, and gas) , “phase” includes these three, but may also apply to many other possible phases of matter– including aqueous (a solid dissolved in water), gel (a jelly-like colloidal mixture) etc. In addition, phase can refer to a boundary between two similar phases that don’t mix, for example, a liquid mixture could have an oily phase and a watery phase that contact each other but do not mix.
Rapid vaporization is called “boiling”,
Slow vaporization is “evaporation”
Sublimation occurs when a material “evaporates” from a solid straight to a gas, like dry ice or iodine.
Terminology associated with
Change of Phase
Eg:NaCl(s) H2O(l) NH3(g)NaCl(aq)
eg: Na(s) + H2O(l) NaOH(aq) + H2(g)
eg: NaCl(aq) Na+(aq) + Cl-(aq) (dissociation of salt)
50g of NH3(g)
72.058 litres NH3(g)
55 g of NH3
Ammonia is a great example, because water can absorb what seems like a huge amount of ammonia gas before it becomes saturated. Mass-wise, its actually half the weight of the water, but volume-wise its over 720 times greater!
Solubility indicates the maximum amount of solute that can dissolve in a given volume of solvent at a given temperature.
CHCl = 2.0 mol/L
[HCl] = 2.0 mol/L
CHCl= 2.0 M
The correct unit for molar concentration is mol/L, although this is sometimes abbreviated with a capital M for molarity
Molar Concentration =
n = CV
C1V1 = C2V2
Where: C1 is the concentration before dilution,
V1 is the volume before dilution
C2 is the concentration after dilution
V2 is the volume after dilution
The pH (positive Hydrogen potential) scale is used to measure the relative acidity or alkalinity of a solution. It is in theory open-ended, but in practice runs from 0 to 14.
* Some salts are slightly acidic (aluminum salts) or slightly basic (carbonates)
Reactants on the Left side of equation
Products on the Right side of equation
(used for balancing)
(s) Solid (l) liquid (g) gas (aq) dissolved in water
Number of atoms in the molecules
*Yes, I am fully aware that the dictionary says that the correct plural of index is indices, but for clarity I am using the term the text uses.
Problem: 8 grams of hydrogen are burned with oxygen to make water. How much oxygen was used?
Step 1: H2 + O2 H2O (skeleton)
2H2 + O2 2H2O (balanced)
Step 2: mole ratios 2 : 1 : 2
Step 3: known reactant is 8g hydrogen. To convert it to moles we must divide by the molar mass of hydrogen, 2.0; That gives us 4 moles of hydrogen. Write this under the corresponding mole ratio 2 : 1 : 2
Step 4: write an x2 : 1 : 2
Step 5: cross multiply 2 = 1 so x = 2 mol
Step 6: to get the answer in grams, multiply the 2 mol by the molar mass of oxygen (32 g/mol) to give us the answer 64 g of oxygen is used.
The words Neutralization and
are also associated with this process
In general: ACID(aq) + BASE(aq) WATER(l) + A SALT(aq)
Example: HNO3(aq) + KOH(aq) H2O(l) + KNO3(aq)
6 CO2 + 6 H2O + energy C6H12O6 + 6 O2
C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy
Error in textbook: On p. 27, respiration is referred to as a “combustion” reaction.
What the textbook means, of course, is that is an “oxidation” reaction.
Salt, ionic crystal lattice
Sugar, covalent molecule
Your textbook has little about metallic bonds, but since we don’t study alloys in detail, this is not a problem.
Sodium has an “extra” electron in its outer shell
Chlorine “needs” another electron in its outer shell
ΔX = 2.23
A crystal lattice structure with alternating ions
Alternating particles do not overlap.
A covalent molecule
A sodium chloride formula unit
Shared electrons in overlapping shells
With Rutherford-Bohr models:
With Lewis electron dot diagrams:
In either case, we draw the atoms to show a stable number of electrons (usually 8) in the outer shell of each atom involved in the covalent bond.
Another way to illustrate covalent bonds is with overlapping circles
p. 30Kinetic Energy
Where: Ek= kinetic energy
m= mass of the object
v= velocity of the object
p. 300.10.2 Potential Energy
Where: Ep = Gravitational Potential Energy in joules
m = mass of the object in kilograms
g = gravitational acceleration (9.8 m/s2 on Earth)
h = height of the object above a reference point (such as the ground)
We will devote a section later in the course to calculating enthalpy.
Where: Em = total Mechanical Energy
Ep = Potential Energy
Ek = Kinetic Energy
Where: Q = amount of heat energy in joules
m = mass of the substance heated in grams (usually the water in a calorimeter)
c = specific heat capacity of the substance heated, in j/g∙°C
ΔT = the change in temperature in °C