Class notes
CHM 113 - General Chemistry I Exam 3 Notes
- Course
- CHM 113 (CHM113)
- Institution
- Arizona State University
This is a note sheet for Exam 3 of General Chemistry I offered at ASU. It contains lecture material and examples.
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Chapter 4 (4.4 - 4.6)Loss of elections is oxidation. Gain of elections is reduction. One cannot occur without the other. The reactions are called redox reaction.
Oxidation Number - A number assigned to each atom in a compound to represent the “charge” each would have if the electrons were divided among the atoms.
Rules for Assigning Oxidation Numbers (ONs):
1. Pure elements (including those that exist as diatomic) are assigned a zero for their ON.
N2 (g)
N - 0, N - 0
2. Monatomic ions have an ON equal to their common charge.
• Metals always have a positive charge.
• Group 1A metals have an ON = +1.
• Group 2A metals have an ON = +2.
• Other metals often have a charge equal to their group number on the Periodic Table. (Does not apply to transition metals that have more than one
oxidation number).
3. The ON of a non-metal depends on what other elements it is bonded to, but can be assigned in the following order:
• Fluorine (F) has an ON of -1, ALWAYS.
• Hydrogen (H) has an ON of +1 (Has an ON of -1 when bound to a metal).
• Oxygen has an ON of -2 (Has an ON of +2 when bound to F and has an ON of -1 when in peroxide, and a -1/2 in superoxide).
• Halogens (Group 7A) have an ON of -1.
4. The sum of all the ONs in a compound/ion must add up to the overall charge of the compound/ion. For neutral compounds, this charge is zero.
Single-Displacement Reactions
• Elements are usually metals (except H2)
• General Pattern: A(s) + BY(aq) → AY(aq) + B(s)
Activity Series
• The most active element appears at the top (more likely to loss election).
• Diagonal Rule: The elemental metal can displace any mental ions on the right and below.
• Hydrogen gas can be replaced out from water or acid.
Concentration and Molarity
• The amount dissolved in a solution is concentration.
• One way to measure the concentration of a solution is molarity.
Dilution
• A solution can be diluted by adding ONLY solvent (i.e., water). The concentration is lower. The moles DO NOT change.
• Only solvent is added during the dilution process.
• For solute:
o Molesinitial = Molesfinal
o Moles = Molarity x Volume (or L)
o Moles = mol/L x L
• Dilution Equation:
o Minitial V initial = Mfinal Vfinal
o Mi Vi = Mf Vf
o M1 V1 = M2 V2
Titration
• A titration is an analytical technique in which one can calculate the concentration of a solute in a solution.
• A solution of known concentration, called a standard solution, is used to determine the unknown concentration of another solution.
• The reaction is complete at the equivalence point, which is based on the seen end point (color change).
Chapter 5
Energy
• Is the ability to do work or transfer heat.
o Work (w) - Energy used to cause an object to move against force (w=Fxd)
o Heat (q) - Energy transferred from a hotter object to a colder object.
• It cannot be created or destroyed.
• It can be converted from one form to another form.
• Every physical and chemical change is accompanied by an energy change.
Kinetic energy is the energy of motion.
• The higher the temperature, the greater the kinetic energy.
• Its magnitude depends on the object’s mass and its velocity: KE = 1/2 mv 2
Potential energy of an object depends on its relative position compared to other objects. It is stored energy from attraction/repulsions.
• The lower the potential energy of the system, the more stable it is.
Energy Units
• 1 Joule (J) = 1 Newton (N) x meter (m) = 1 J = 1 kg m2 / s2
System and Surroundings
• The portion of the universe that we single out to study is called the system.
o A chemical reaction represents a system.
• The surroundings are everything else.
• System + Surroundings = Universe
• The total energy of the universe is constant.
Types of Systems
• Open System - A region of the universe being studied that can exchanged energy and matter with its surroundings.
• Closed System - A region of the universe being studied that can only exchange energy with its surroundings (not matter).
• Isolated System - A region of the universe that cannot exchange energy or matter with its surroundings.
Internal Energy (E)
State Functions
• Enthalpy (H)
• Pressure (P)
• Internal Energy (E)
• Volume (V)
Path Functions
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