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Midterm

CHEM 130 Study Guide - Midterm Guide: Allotropes Of Phosphorus, Oxygen, Lithium Hydroxide


Department
Chemistry
Course Code
CHEM 130
Professor
All
Study Guide
Midterm

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CHAPTER 1
Physical properties: A characteristic that can be observed for a material without changing
its chemical identity
Soft, silver colored, melting point (64 degrees)
Chemical Properties: A characteristic of a material involving a chemical change
Reacts with water, reacts with oxygen etc
Heterogeneous mixture: Mixture that consists of physically distinct parts, each with
different properties
Salt and iron filings, oil and water
Homogenous Mixture: A mixture that is uniform in properties, also called a solution
Saltwater, air etc
Significant figures: digits in a measured number (or a result of a calculation of measured
numbers) that include all certain digits plus a final one having some uncertainty
· Multiplication and Division
· Keep the smallest number of significant figures
· Addition and Subtraction
· Keep the smallest number of decimal places
· Exact Numbers
· Counted numbers
· Definitions and conversion factors
· Have an infinite number of significant figures
· Rounding
· Look at the first digit to the right of the last significant figure
5, round up
< 5, round down
CHAPTER 2
Important Scientists/Experiments
· Scientist Experiment Result
JJ Thomson Cathode Ray Tube Discovery of the electron
Robert Millikan Oil Drop Charge of the electron
Ernest Rutherford Gold Foil Positively charged nucleus
John Dalton Atomic theory Matter is composed of atom
Cathode Ray Tube: Glass tube showing rays. Cathode rays bend toward (+) end of
magnet and that means they are negatively charged
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Exam 1 Study Guide

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Oil Drop: Dropped oil into chamber which determined charge of various oils and he
found smallest changes in charge.
Gold Foil: used positively charged alpha particles to bombard thing gold foil. Most
particles passed through foil, but few deflected off at large angles. (nucleus and
mostly empty space around it)
·Mass Number: protons + Neutrons
·Isotopes: where elements have same atomic number (number of protons) but change
their number neutrons (mass number)
Nomenclature
Writing Names from Formulas
General Rules
¨ Name the cation first, then the anion.
cation = positive ion (think ca+ion)
anion = negative ion (think "n for negative")
¨ If the anion is not polyatomic, change the ending to "-ide."
Ionic compounds (Metal + nonmetal)
¨ Naming scheme: metal (#) nonmetal -ide
¨ The number is the oxidation state (charge) of the metal, written as a
roman numeral (e.g. manganese (IV) = Mn4+)
*Charges greater than +7 are rare, and even +7 is not particularly common.
If a metal has only one charged state (everything aside from transition metals), the
Roman numeral is left off.
¨ Group 1A (1) metals (Li, Na, K, Rb, Cs, Fr) are always +1
¨ Group 2A (2) metals (Be, Mg, Ca, Sr, Ba, Ra) are always +2
¨ Silver (Ag) is always +1
¨ Zinc (Zn) and cadmium (Cd) are always +2
¨ Aluminum (Al) and Gallium (Ga) are always +3
e.g. CaCl2 = calcium chloride, NOT calcium (II) chloride
Determining the oxidation state of the metal
· Write the metal cation as having a +x charge.
· Write the anion with its charge.
· Balance the charges and find x.
Covalent compounds (Non-metal bound to non-metal)
· Naming scheme: prefix-cation prefix-anion
· The prefixes are Greek and indicate the number of that atom
type.
mono- = 1 tetra- = 4 hepta- = 7 deca- = 10
di- = 2 penta- = 5 octa- = 8
tri- = 3 hexa- = 6 nona- = 9
e.g. P4S3 = tetraphosphorus trisulfide
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¨ Mono- is left off for the first atom.
e.g. CO 2 = carbon dioxide, NOT monocarbon dioxide
¨ Polyatomic ion names are NOT replaced by prefix-style
naming
e.g. NH4Cl = ammonium chloride, NOT nitrogen
tetrahydrogen chloride
Writing Formulas from Names
Covalent compounds
· Use the prefix for the number of each atom present
(e.g. SF6 = sulfur hexafluoride)
Ionic compounds
· Write the metal ion with its charge, and the anion with its
charge.
· Balance the charges and find the coefficients.
· Write the coefficients from balancing as the subscripts for each
ion.
Determining the charge of a common ion
· Cations
¨ 1-18 group numbering system: 18 - group # = anion charge
¨ 1A-8A group numbering system: 8 - group # = anion charge
e.g. carbon is in group 14 (or 4A)
¨ 1-18 system: 18 - 14 = 4 C4+
¨ 1A-8A system: 8 - 4 = 4 C4+
Hydrogen (H) usually becomes +1
Carbon (C) usually becomes +4
· Anions
¨ 1-18 group numbering system: group # - 18= anion charge
¨ 1A-8A group numbering system: group # - 8 = anion charge
e.g. chlorine is in group 17 (or 7A)
¨ 1-18 system: 17 - 18 = -1 Cl
¨ 1A-8A system: 7 - 8 = -1 Cl
Fluorine (F) always becomes –1
Hydrogen (H) becomes –1 when bound to a metal
Oxygen (O) almost always becomes –2, O is called a
peroxide and always comes in pairs (O22–)
Molecular Compounds: Formula shows exact number of atoms in each molecule
Ionic Compounds: formula is the simplest ratio of ions
Balancing Reactions
Make sure all moles (atoms) for each element are equal on both sides of the reaction. Can
not have any half numbers, all number must be whole
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