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Transcript of A.P. Chemistry
Summer Review H.W.
By: Azka Fatima Ali
Kinetics and Equilibrium
Moles and Stoichiometry
I have clearly explained 4 concepts from each of the 10 core topics in chemistry. I've provided diagrams, practice questions, and basic terminology and explanations for the concepts.
Physical Behavior of Matter (solutions included)
Oxidation and Reduction
Chemistry core Topics
1.1 The modern model of the atom has evolved over a long period of time through the work of many scientists.
* Thomas Model of the Atom: The atom is a hard sphere of positive charges with electrons (negative charges) in it.
* Rutherford Model of the Atom: Most of the mass of the atom is in the center, the nucleus, which is positive. Protons are in the nucleus. Most of the atom is empty space. Electrons go around the nucleus,
*Bohr Model of the Atom: Protons are in the nucleus, which is positive. Electrons go around the nucleus in concentric circular orbits.
* Modern Model: Wave Mechanical Model (Electron Cloud). Protons are in the nucleus. The electron cloud model shows that an electron is in an orbital, which is the most probable place an electron is .It shows the electron as a spread out cloud of negative charge. The thickest place is where you'll most likely find the electron. The thinnest part of the cloud is the least likely place to find the electron. When an electron goes from an orbital which has more energy to an orbital which has less energy, a spectrum (colors, energy) is given off.
1.9 When an electron in an atom gains a specific amount of energy, the electron is at a higher energy state excited state.
An atom is excited when the electrons have absorbed energy or gotten more energy. The electrons jump ahead to a higher energy level, leaving one of the inner principal energy levels partly empty.
Which is an electron configuration of an electron in the excited state?
1. 2-8-2 2. 2-8-1 3. 2-7-1 4. 2-8-3
*Solution: Answer 3
The first energy level can hold 8 electrons. In choice 3, there are only 7 electrons in the second principal energy level, because one electron jumped ahead to the third principal energy level. The second principal energy level can hold 8 electrons and since it has 7, it is partially empty.
Principal Energy Levels
First principal energy level can hold 2 electrons.
Second principal energy level can hold 8 electrons.
Third principal energy level can hold 18 electrons.
Fourth principal energy level can hold 32 electrons.
1.10 When an electron returns from a higher energy state to a lower energy state, a specific amount of energy is emitted. This emitted energy can be used to identify an element.
When the excited electrons go back to lower energy levels, they giver off energy (in specific amounts called Quanta), which produces a spectrum of colors, or Bright Line Spectrum. Excited electrons from different atoms of the same element return to different energy levels. In some sodium atoms, the excited electrons go back from the energy level of 3 to the energy level of 2, while in other sodium atoms the excited electrons go back from the energy level of 3 to the energy level of 1, producing a bright line spectrum. A bright- line spectrum helps to identify the element because each element has a different bright-line spectrum. For example, if you have an element and you want to see if its lithium, compare the bright-line spectrum of the sample that you have with the bright- line spectrum of lithium.
1.13 The average atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes.
The atomic mass of an element is the weighted average mass of the naturally occurring isotopes of that element. The average is weighted according the proportions in which the isotopes occur. For example, there are two isotopes of chlorine that have the same atomic number but different masses. The two isotopes of chlorine are: 17Cl with the mass of 35 and 17Cl with the mass of 37. If you look at the periodic table, the atomic mass of 17Cl is 35.5 atomic mass units, which is the average weight of all the isotopes. Atomic mass is given in the mass units (amu). Since the atomic mass , average weight 35.5 amu, is closer to the atomic mass 35 than to the atomic mass 37, there is more of the isotope 17CL (with the atomic mass of 35) and it is the abundant isotope.
There is 25% of the naturally occurring isotope 17Cl (with the mass of 37) and 75% of the naturally occurring isotope 17Cl (with the mass of 35). What is the atomic mass of the element?
*Solution: Take the percentage of each isotope times its mass and then add the numbers.
17Cl (with mass of 37) .25 *37 =9.25
17Cl (with mass of 35) .75 * 35 =26.25 ADD 9.25 AND 26.25 AND YOU'LL GET 35.50 AMU.
111.3 Types of chemical formulas include empirical, molecular, and structural
* Chemical formulas describe the composition of elements or compounds. Formulas can be empirical, molecular, or structural.
*A molecular formula indicates the total number atoms of each element needed to form the molecule:
6 atoms of carbon, 12 atoms of hydrogen, 6 atoms of oxygen
* An empirical formula is the simplest formula in which the atoms combine to form a compound. For example, if the molecular formula is
divide the C, the H, and the O, by the
largest number the elements can be divided by, 6, in order to get the empirical formula.
*A structural formula shows how the atoms are joined or connected to each other in a molecule.
If you still don't understand how to write imperial and molecular formulas check out this video.
111.4 In all chemical reactions there is a conservation of mass energy and charge.
Conservation of Matter: In all chemical reactions matter stays the same. Matter can't be destroyed and the total matter (# of grams) on one side of the equation is the same on the other side of the equation.
Ex: 2H(II) + O(II) 2H(II)O
There is a conversation of matter because there is the same number of oxygen atoms (2) and hydrogen atoms (4) on both sides of the equation.
Conservation of Energy : In all chemical reactions there is a conservation of energy. Energy can not be crated or destroyed. The total amount of energy on one side of the equation equals the total amount of energy on the other side of the equation.
Conservation of Charge: The total amount of charge is equal on both sides of an equation,
EX: Na Na+ + e-
Before the arrow: Na or any element by itself has a charge of .
After the arrow: Na, charge of +1 and 1 electron, (charge=1)=0.
111.8 Types of chemical reactions include synthesis, decomposition, single replacement, and double replacement.
Synthesis reaction: Two or more elements or simpler compounds unite to form a compound.
Na + Cl NaCl (sodium chloride)
Decomposition Reaction: A compound is broken into two or more elements or simpler compounds.
Nacl Na + Cl
Single replacement reaction: A free element (an element alone such as iron, Fe) replaces an element that is part of a compound.
Fe (iron) + CuSO(IV) (copper sulfate) FeSO(IV) (iron sulfate) + Cu (copper)
Double replacement reaction: Two elements replace eachother or switch partners.
NaCl + AgNO(III) NaNO(III) + AgCl
sodium silver sodium silver
chloride nitrate nitrate chloride
111.6 The formula mass of a substance is the sum of the atomic masses of its atoms. The gram formula mass (molar mass) of a substance equals one mole of that substance.
* Formula mass is the sum of the atomic masses in the molecule.
What is the formula mass of K(II)CO(III)?
solution: Look at the atomic masses of the elements in the Periodic table.
The atomic mass of K is 39, but since you have k2, multiply 39 by 2 to get 78.
Atomic mass of K=39
The atomic mass of C is 12.
The atomic mass of O is 16, but you have O3, so multiply 16 by to get 48.
Now add 78+12+48=138
Gram Formula Mass
The gram formula mass is the mass of 6.02*10^23.
6.02*10^23 particles= 1 mole of particles
To find the gram formula mass take the formula mass, like the one for K2CO3, and add the word grams. So the gram formula mass of K(II)CO(III) is 138 grams.
*gram formula mass = molar mass
VI.1 Collision theory states that a reaction is most likely to occur if reactant particles collide with the proper energy and orientation.
This diagram explains that the a reaction will only occur properly if it happens that way demonstrated below the diagram.
VI.2 The rate of chemical reaction depends on several factors: temperature, concentration, nature of reactants, surface area and the presence of catalyst.
*Concentration: When the concentration of the reactant(s) increases, the rate o reaction increases.
*Temperature: Increase in temperature increases the rate of reaction.
*Surface Area: Increasing the surface area increases the rate of reaction
*Nature of Reactants: A reaction that involves the smallest amount of bond rearrangement is fast.
* Catalyst: A catalyst lowers
activation energy and gives a
faster rate of reaction.
VI.5 LeChatelier principle can be used to predict the effect of stress ( change in pressure, volume, concentration, and temperature) on a system at equilibrium.
Change in concentration:
Left side R Right Side
A + B C + D
An increase in concentration
of anything on the left side (A
or B) causes the reaction to go
to the right side (C or D) causes the
concentration to go to the left side.
Change in Pressure
has an effect only on a gas. If the
pressure on an equilibrium system is increased, the reaction is driven in the direction that relieves the pressure, in the direction of less gas molecules.
Change in temperature:
The addition of heat, accoriding to LeChatelier's Principle shifts equilibrium so that heat is absorbed (to relieve stress).
Change in Volume:
If the volume is increased the equilibrium will shift to the higher pressure side.
VI.7 Energy released or absorbed by a chemical reaction can be represented by a potential energy diagram.
If products have less potential energy or heat content than reactants, heat is given off and its an exothermic reaction.
In endothermic reactions, the reactants take in the heat and form the products. In endothermic reactions the products are higher up than the products have more potential energy than teh reactants.
VIII.4 Oxidation is the loss of electrons.
Na a metal and metals lose electrons to have a complete outer shell. Na loses an electron and becomes Na^+ ion. Na (sodium) is oxidized and is a reducing agent. When Na loses an electron, it causes something else to gain it and become reduced.
VII.2 Reduction is the gain of electrons.
When electrons are gained (negative particles) the oxidation number decreases..
F + e F-; its oxidation number decreases from 0 to -1. Fluorine gains one electron to have 8 electrons in the outer shell. F gains an electron. F is reduced. It is an oxidizing agent.
VIII.9 A voltaic cell spontaneously converts chemical energy to electrical energy.
*A voltaic cell is a type of electrochemical cell.
*A voltaic cell uses redox reactions that are spontaneous to produce electricity. A battery is an example of a voltaic cell.
There are two half cells. In each half cell is a metal strip called an electrode. There is a wire connecting two electrodes. Electrons travel through the wire. There is a salt bridge connecting to half cells to permit IONS to flow between the two half cells.
Direction of flow in a voltaic
cell is from the anode to
VIII.10 An electrolytic cell requires electrical energy to produce chemical change. This process is known as electrolysis.
Example: Electrolysis in water
Electricity breaks down water into hydrogen and oxygen.
2H(II)O electricity 2H(II)+O(II)
* Electrolytic cells have ANODE-OXIDATION and CATHODE-REDUCTION.
* In electrolytic cells polarities are reversed: the anode is positive and the cathode is negative.
II.3 Elements can be classified by their properties and located on the Periodic table as metals, nonmetals, metalloids ( B, Si, Ge, As, Sb, Te), and noble gases.
*Metals: Elements to the left of the the zigzag line on the Periodic table are metals. Metals have low ionization energy and low electronegativity. Metals have metallic luster (shine), are malleable (can be made into sheets), and ductile (can be made into wires). Metals are good conductors of heat and electricity.
*Nonmetals are elements to the right side of the periodic table, except group 18 which are the noble gases. Nonmetals have high ionization energy and high electronegativity. Nonmetals tend to gain electrons when they react with other metals. They lack metallic luster, are brittle, and are poor conductors of heat and electricity.
*Metalloids are elements touching the zig zag line on the periodic table. These elements have some properties of metals and nonmetals
*Noble Gases are in group 18. Elements in group 8 have 8 valence electrons (except for helium).
Noble gases are monatomic gases: Atoms in this group have a complete outer principal energy level and are stable.
11.5 Elements can be differentiated by chemical properties. Chemical properties describe how an element behaves during a chemical reaction.
*The chemical property of an element of an element describes how a chemical reacts in a chemical reaction. Does it burn? Does is react with water, acid, etc.?
*Elements in group 1 react faster than elements in group 2 because it's easier to lose 1 valence electron than to lose 2 valence electrons.
Ex: Sodium (Na) from group 1 reacts vigorously in cold water, while Magnesium (Mg) from group two reacts slowly in only hot water.
*As you go down groups 1 and 2 reactivity increases.
*For nonmetals in a group the rule is that the top one is more active than the elements beneath it.
EX: Fluorine is more active than Cl, and Cl is more active than Br.
*Table s in the reference tables lists the physical and chemical properties of elements, such as melting point, boiling point, density and electronegativity.
* Melting point: 1808 K
* Boiling Point: 3023 K
* use table t to convert
1808k into clesius
11.2 The number of protons in an atom(atomic number) identifies the element. The sum of protons and neutrons in an atom (mass number) identifies the isotope.
-Atomic number is located in the bottom left in the lower left hand corner.
-Atomic Mass is at the top left corner.
1. what is the name and atomic mass of the element that has the atomic number of 18?
Solution: Go to the Periodic table and identify 18 on the bottom left hand corners. Once you find it, identify the name (Ar stands for argon) and look at the top left hand corner for teh atomic mass which is 39.948.
11.1 The placement or location of elements on the Periodic Table gives an indication of physical and chemical properties of that element. The elements on the Periodic Table are arranged in order of increasing atomic number.
*Elements in group 1 react faster than elements in group 2.
* As you go down groups 1 and 2 reactivity increases.
* For nonmetals, the top one is more active than the elements beneath it.
Density tends to increase as you go down the group.
Both the melting and
boiling points fall as you go down the group.
V.2 The three phases of matter (solid, liquid, and gas) have different properties.
1. During which phase of matter are particles close together in fixed positions?
In solids, particles are fixed together because there is the strongest force of attraction between them.
V.6 The proportions of components in a mixture can be varied. Each component in a mixture retains its original properties.
Mixture- Salt and water mixed together
*In a mixture two or more substances (salt and sugar) are mixed together not united
*A mixture can have different proportions: 1/2 cup salt mixed with 1/2 cup sugar or 3/4 cup salt mixed with 1/4 cup sugar
* In mixture, each substance still has its own properties. Salt still has the salty taste and sugar still has the sweet taste.
salt salt &sugar sugar
V.11 Energy can exist in different forms such as, chemical, electrical, electromagnetic, thermal, mechanical, and nuclear.
Explanation & Notes:
*Chemical energy: Energy released or absorbed in a chemical reaction. Chemical energy changes into heat energy
ex: burning coal
*Electrical Energy: Energy of flow of electrons (moving electrons)
*Electromagnetic Radiation: Energy made up of waves, including gamma rays, ultraviolent, light, radio waves etc.
*Thermal energy: Random motion of atoms and molecules
*Mechanical Energy: Energy in moving objects.
ex: rock falling, car moving
*Nuclear Energy: Energy given off when a nucleus beaks up into smaller nuclei or when smaller nuclei unite to form a larger nucleus.
v.9 The concentration of a solution may be expressed as molarity (M), percent by volume, percent by mass, or parts per million (ppm).
* molarity=moles of solute/ liters of solution
*percent mass= mass of part/ mass of whole *100%
*percent volume= volume of solute/volume of solution*100
*ppm= grams of solute/ grams of solution* 1,000,000ppm
What is the molarity of a solution that cintains 4.0 mol of NaOH in .50 L of solution?
Solution: Identify the known and unknown values.
amount of NaOh= 4.0 mol
volume of solution= 0.50 L
molarity = ?M
Substitute known values into the equation for molarity, solve for molarity.
M= moles of solute/ liters of solution
M=4.0 moles NaOH/0.50 liter
VII.2 Hydrocarbons are compounds that contain only hydrogen and carbon. Saturated hydrocarbons contain
only single carbon- carbon bonds. Unsaturated hydrocarbons contain atleast one multiple carbon-carbon
- end in "ane"
- Each of the prefixes
meth-, eth-, etc... are
associated with a different
number of carbon atoms
- Use table P for organic
- one double bond
- end in "ene"
ethene, propene, pentene,
butene, and octenes
- Each of the prefixes,
eth-, prop-, etc.. are
associated with a
of carbon atoms
VII.4 Isomers of organic compounds have the same molecular formula but different structures and properties
Molecular Formula of pentane:
There are three isomers of pentane who all have 5 C atoms and 12 H atoms, thus having the same molecular formula.
VII.6 Types of organic reactions include: addition, substitution, polymerization, esterification, fermentation, saponification, and combustion
*Substitution: Replacement of one kind of atom or group by another kind of atom or group
- Substitution only happens in alkanes because they have single bonds between carbon atoms
* Addition: Adding one or more atoms at a double or triple bond
- Addition only happens in alkenes and alkynes because they have double or triple bonds
*Fermentation: Yeast cells secrete the chemical enzyme zymase and break the six chain of sugars into carbon dioxide and two carbon fragments of alcohol
Esterification: Acid and alcohol produce ester and water
Ethanoic acid + methanol methyl + water
* Saponification (hydrolysis) is an ester breaking up into acid and alcohol (reverse of esterification)
fat ( + strong base) soap + glycerol
(ester) salt of acid alcohol
* Combustion: Combustion mans burning (reacting with oxygen). Hydrocarbons burn ( unite with oxygen) to form carbon dioxide and water. In a limited supply of oxygen, carbon and carbon monoxide are formed.
Polymerization: Involves smaller molecules joinging together to form one big molecule.
-A monomer is a smaller molecule
- A polymer is a large molecule
- Monomers join to form a polymer
amino acid + amino acid + amino acid = protein
- There are two types of polymerization
a. Condensation Polymerization
b. Addition Polymerization
VII.3 Organic acids, alcohols, esters, aldehydes, ketones, ethers, halides, amines, amides, and amino acids are categories of organic molecules that differ in structure. Functional groups impart distinctive physical and chemical properties to organic compounds.
-Hydrocarbons are the most basic organic compounds.
- Other organic compounds form when other atoms replace one or more hydrogen atoms in a hydrocarbon.
-These atoms or groups of atoms are called functional groups, and they replace hydrogen atoms in a hydrocarbon, giving the compound distinctive physical and chemical properties.
- The chart provided above in Table R form the Chemistry reference table. All of the organic compounds differ in structure.
IV.2 Two major categories of compounds are ionic and molecular (covalent) bonds.
*Covalent Bond: Forms when two nuclei share electrons in order to achieve a stable arrangement of atoms. This usually forms between two non-metal atoms of the same element. Chlorine (II), a diatomic chlorine molecule, is an example of a covalent bond.
*Ionic Compound: Forms when ions (charged particles) bond together because of the electrostatic attraction of oppositely charged particles.
What are the different types of covalent bonds?
Properties of molecules
*Molecules are generally associated with covalent bonds. They are:
- poor conductors of heat
-poor conductors of electricity
-low melting points
-low boiling points
-high melting point
- high boiling point
IV.5 Molecular polarity can be determined by the shape of the molecule and the distribution of charge. Symmetrical (non-polar) molecules include CO(II) and CH(IV). Asymmetrical molecules include HCl, NH(III), and H(II)O.
*Molecular polarity can be determined by just looking at the atoms.
*If atoms in the molecule are symmetrical, the charges are balanced by each other and the molecule is considered non-polar.
* If the atoms in the molecule are asymmetrical it is considered to be polar.
Polar Vs. Non-polar
Lewis Dot Structures: Consists of a chemical symbol surrounded by one to eight dots representing valence electrons.
iv.10 Electron dot diagrams (Lewis structures ), can represent the valence electron arrangement in elements, compounds, and ions.
IV.12 The electronegativity difference between two bonded atoms is used to assess the degree of polarity in the bond.
As electronegativity differecen between two atoms in a bond increases, the bonds become more polar in nature.
* As electronegativity difference increases, the bonds become more ionic in character.
X.I Stability of isotopes is based on the ratio of neutrons and protons in its nucleus. Although most nuclei are stable, some are unstable and spontaneously decay, emitting radiation.
*Most nuclei are stable if they are found within the belt of stability. t is the ratio of neutrons to protons that determines the stability of a nucleus.
* The ratio of all nuclei with atomic numbers greater than 83 makes those nuclei unstable.
Belt of Stability
X.4 Spontaneous decay can involve the release of alpha particles, beta particles, positrons and/or gamma radiation from the nucleus of an unstable isotope.These emissions differ in mass, charge, ionizing power, and penetrating power.
*Alpha particle: a helium nucleus composed of two protons and two neutrons. It is represented by the symbol 4/2He or Greek letter alpha.
*Beta particle: An electron whose source is an atomic nucleus.
*Positron: Is identical to an electron except that it has a positive charge.
*Gamma rays: Almost all nuclear decay releases some energy in the form of gamma rays, which are similar to x-rays but have a greater charge.
Alpha Emission :
-Characteristic of heavy nuclei
-Common in atoms with nuclei with an atomic number greater than 82
-atomic number decreases by two
- number of protons decreases by two
-number of neutrons decreases by two
-mass number decreases by four
greek letter alpha
-Nucleus that emits a beta particle, goes through beta decay and is called a beta emitter
Beta Decay Summary:
-atomic number increases by one
-number of protons increases by one
-number of neutrons decreases by one
-mass number remains the same
-atomic number decreases by one
-number of protons decreases by one
-number of neutron increases by one
mass number remains the same
A or a = mass number Z or z = charge; atomic
X = original element x = radioactive emission
X.7 Nuclear reactions can be represented by equations, that include symbols which represent atomic nuclei (with the mass # and atomic #), subatomic particles (with mass # and charge), and /or emission such as gamma radiation.
X.6 There are benefits and risks associated with fission and fusion reactions.
-Fission reactions provide produce a great deal of energy, which is used to produce electric power.
Fusion reactions take place in the sun and produce tremendous amounts of solar energy.
-In both reactions, the total mas of the new nuclei formed is much less than the mass of the original material. Some mass is converted into energy.
-Fusion reaction releases much more energy than a fission reaction.
-Risks from fission reactions in nuclear reactors are very radioactive.
-They must be stored for more than 100,000 years without leaking into the environment.
-Some of these nuclear wastes have long half-lives. Therefore, more radioactive material remains and it is more dangerous
-Another risk is that accidents and fires in reactors release can release dangerous levels of radioactivity (giving off rays and particles).
-Workers and the public can become sick from too much radiation from fission reactions.
Acids, Bases, and Salts
IX.1 Behavior of many acids and bases are explained by the Arrhenius theory. Arrhenius acids and bases are electrolytes.
*The properties of an acid are because of H+ ions and the properties of a base are because of OH- ions.
*Acids and bases conduct electricity (are electrolytes) because they form ions.
*Acids and bases form salt and water. They H+ from acid combines with the OH- from the base to form water.
IX.7 There are alternate acid-base theories. One theory states that acid is an H^+ donor and a base is an H^+ acceptor.
HCL(g) to H(II)O(liquid) H(III)O+(aq)0 +Cl-(aq)
donates H^+ (a proton)
*According to the alternate base theory , HCl is an acid because it is an H+ donor. It gives away H+ to H(II)O and Cl^- is left.
* According to the alternate acid-base theory, H(II)O is a base because it is a H^+ acceptor. H(II) accepts H^+ (a proton) which HCl gives away.
IX.5 In the process of neutralization, an Arrhenius acid and an Arrhenius base react to form salt and water.
*Acid neutralizes base or base neutralizes acid because there are equal amounts of H+ (from the acid) and OH (from the base).
IX.3 Arrhenius acids yield H+(aq), as the only positive ion in an aqueous solution The hydrogen ion may be written as H(III)+(aq), hydronium ion.
*What do Arrhenius acids have?
They have H and yield H+.
*In what aqueous solutions do they yield H+?
HCl, HBr, and H(II)SO(IV) are Arrhenius acids and have H and yield H+ ions in solutions.
*What are H+ ions always attached to?
H+ are always attached to H(II)O, forming H(III)O+ (hydronium ions).
What substance can be classified as an Arrhenius acid?
a.HCl b.Nacl c. LiOH d. KOH
Solution: a. Hcl because it has H and gives off H+ ions in solution.