Gen Chem

• Chemistry is the science of matter, which includes properties, compositions, structure, changes, and laws of matter
• Matter is anything that occupies space and has mass
• There are 5 major branches of Chemistry:

  • Organic: compounds with Carbon; study of most carbon-based compounds
  • Inorganic: study of compounds not organic
  • Physical: application of physical laws to chemical change and systems
  • Biochemistry: chemistry of life processes and living organisms
  • Analytical: analysis on composition of matter
• Chemistry plays a crucial role in society and industry:

  • Industry depends on chemistry
  • Many professions and occupations require knowledge of chemistry
  • The application of chemistry theories produces new and better materials
  • Everyday experiences can be explained by chemistry
• Characteristics of particles of matter:

  • Particles are extremely small
  • Particles are continuously moving (Brownian movement)
  • Particles attract with one another
  • Particles have gaps or spaces within
• Phases of matter:

  • Solid:
  • Tightly packed, do not move, have definite shape and volume
  • 2 types: Crystalline (with unit cells and definite shape) and Amorphous (no definite pattern)
  • Liquid:
  • Spread apart, moves slowly, has definite volume, flows
  • Viscosity (resistance to flow)
  • Gases:
  • Very far apart, move rapidly, high compressibility, low density, weak attraction, expands when heated
  • Plasma:
  • Temperature > 3000°C, consists of charged particles
  • Bose-Einstein Condensate:
  • Coldest solid, barely moving, lowest energy, extremely close together
• Compositions of matter:

  • Democritus proposed the word "Atom" as indivisible
  • Aristotle opposed Democritus' idea
  • Brownian movement: particles move in a zigzag motion
• Kinetic Molecular Theory:

  • All atoms are made up of tiny particles
  • Particles are in constant motion
  • Collisions between particles or container are perfectly elastic (no energy lost)
• Properties of matter:

  • Physical properties can be measured or observed without changing identity
  • Intrinsic/intensive properties don't depend on quantity
  • Extrinsic/extensive properties depend on quantity
  • Chemical properties change the identity of the subject, can't be returned to original form
• Classifications of matter:

  • Pure Substance:
  • Homogeneous, consists of only one kind of matter with definite composition
  • Element: simplest form of matter, cannot be decomposed
  • Compound: chemically combined elements with definite composition
  • Mixture:
  • Physical combination of two or more substances without changing properties
  • Homogeneous: one phase, evenly distributed components
  • Heterogeneous: two or more substances, identifiable parts
• • Floatation: allows solute to float in solvent
• Ways to separate mixtures:

  • Filtration: separates solids and liquids using porous barriers
  • Distillation: separates homogenous mixtures based on boiling point differences
  • Evaporation: separates soluble solutions
  • Crystallization: purifies solids by forming pure solid particles
  • Centrifuging: separates based on density differences
  • Magnet: separates metal and non-metal substances
  • Chromatography: separates color pigments based on attraction
  • Decantation: allows solid particles to settle and removes liquid
  • Sieving: separates substances based on size differences
• Measurement:

  • Accuracy: nearness of measurement to accepted value
  • Precision: nearness of two or more measurements to true value
  • Sources of error in measuring: instrument used, human error or skills, parallax
• Significant Figures:

  • Estimated values with certainty for the few first numbers
• Significant Figures:

  • Every non-zero digit is significant
  • Zeroes between non-zeros are significant
  • Zeroes appearing in front of non-zero digits are not significant
  • Zeroes at the end of a number and to the right of a decimal point are significant
  • Zeroes at the end of a number and to the left of a decimal point are not significant
  • Zeroes between non-zero digits are significant
  • Numbers written in scientific notation consider only the base
• Arrow Technique:

  • For decimal point: move left to right until a non-zero digit is reached
  • For whole numbers: move right to left until a non-zero digit is reached
• Handling Significant Figures in Calculations:

  • Addition/Subtraction: Final answer should have the same number of decimal places as the given value
  • Multiplication/Division: Result should have the same number of significant figures as the least precise value
• Density:

  • Mass/Volume
  • Intensive potential
  • SI Unit is kg/m^3 or g/cm^3 or g/ml
• Atoms and Atomic Structure:

  • Early Ideas:
  • Thales of Melitus: everything is composed of matter
  • Anaxagoras: everything has its own kind of "seed" that is clustered together
  • Empedocles: everything is composed of the 4 elements in nature
  • Leucippus and Democritus: introduced the concept of "atom" as indivisible and uncuttable
  • Aristotle: opposed Democritus' idea of indivisible atoms
• Assumptions of John Dalton:

  • All matter is composed of indivisible and indestructible atoms
  • All atoms of a given element are identical
  • Atoms rearrange during physical or chemical changes
  • Atoms of different elements combine in a definite ratio to form compounds
• Laws in Chemistry:

  • Law of Definite Proportion/Composition: chemical compounds have a fixed ratio of elements
  • Law of Conservation of Mass: mass is neither created nor destroyed in an isolated system
  • Law of Multiple Proportions: when elements form compounds, the ratio of masses is a small whole number
• Fundamental Sub-Atomic Particles of an Atom:

  • Electrons: negatively charged particles located outside the nucleus
  • Protons: positively charged particles found inside the nucleus
  • Neutrons: uncharged particles found inside the nucleus
• Basic Structure of an Atom:

  • Nucleus: central part containing protons and neutrons
  • Atomic Number (Z): number of protons and electrons
  • Mass Number (A): total number of protons and neutrons in the nucleus
• How Ions Form:

  • Anions gain electrons and have a negative charge
  • Cations lose electrons and have a positive charge
• Isotopes:

  • Atoms of the same element with different mass numbers
  • Hyphen notation is used to distinguish isotopes
• Average Atomic Mass:

  • Weighed average of all isotopes
  • Rounded to two decimal places
• Naming and Writing Chemical Formulas:

  • Ionic Compounds: metal + non-metal, name metal first followed by non-metal with "-ide" ending
  • Covalent Compounds: use Greek prefixes to represent the number of atoms of each element
  • Metal with more than one oxidation number: classical system uses "-ous" and "-ic" endings, Stock system uses Roman numerals
  • Metal + polyatomic ion: write the metal name followed by the polyatomic ion name
  • Binary Acid: starts with hydrogen and non-metal
  • Ternary Acid (oxyacids): contains three or more elements
• Hydrogen:

  • Acid with 2 elements (H + non-metal)
  • Aqueous solution (aq.)
  • Example: HCl (aq) → Hydrochloric acid
• Ternary acid (oxyacids):

  • 3 or more elements
  • With oxygen
  • H + radical
  • Radicals ending in -ate change into -ic acid, -ite change into -ous acid
  • Example: HNO2 → Nitrous acid
• Hydrates:

  • Some compounds have water molecules attached as parts of their structure
  • With water (salt and water separated by a dot)
  • Example: CuSO4 . 5H2O → Cupric Sulfate . Pentahydrate or Copper (II) Sulfate. Pentahydrate
• Mole concept:

  • Mole: Unit used in counting particles
  • n or mol
  • Mass spectrometer: 6.02 x 10^23 (Avogadro’s number) → Amadeo Avogadro
  • Atom → element; molecule → compound
• Conversion factor:

  • 6.02x10^23 particles / 1 mole or 1 mole / 6.02x10^23 particles
  • Example: 2 moles of monosodium glutamate or vetsin
  • Given: 2.00 moles of monosodium glutamate
  • Unknown: no. of particles (molecules)
  • Calculation: 2 x (6.02 x 10^23 of MSG molecule/1 mole) = 1.20 x 10^24 molecules msg
• Molar mass:

  • The mass in grams that is numerically equal to the atomic mass
  • Unit: g/mol
  • Other names related to molar mass: Molecular mass/molecular weight, Formula mass/weight
  • Example: K2O
  • Calculation: K = 2 x 39.10 = 78.20, O = 1 x 16.00 = 16.00, 78.20 + 16.00 = 94.20 g/mol
• Calculations with molar mass:

  • Grams ← molar mass → moles
  • Example: Aluminum is used for bikes. How many grams of Al are in 3.00 moles of Al?
  • Given: 3.00 mol Al = 26.98 grams of Al
  • Unknown: g Al?
  • Calculation: 3.00 mol Al x (26.98 g Al/1 mol Al) = 80.9 g Al
• Avogadro’s number + molar mass:

  • Grams ← molar mass → moles ← Avogadro’s no. → particles
  • Example: How many atoms of K are present in 78.4 g of K?
  • Calculation: 78.5 g K x (1 mole K/39.10 g) x (6.02 x 10^23 atoms / 1 mole K) = 1.21 x 10^24 atoms of K
• Percentage composition:

  • Percent by mass of each atom of an element in a compound
  • Always the same regardless of the amount
  • Calculation: Mass of element in 1 mole / molar mass x 100 = % of element in compound
  • Example: Calcium Chloride
  • Calculation: Ca= 36.11%, Cl= 63.89%
• Empirical formula:

  • Tells the ratio of atoms in a molecule
  • Simplest formula
  • Steps to calculate E.F.
  • Example: Element mass, Atomic mass, Mole, No. of atoms, Multiply ‘til whole
  • Calculation: C3H6O2
• Molecular formula:

  • M.F. or true formula
  • Tells exactly how many of each atom are in the molecules
  • Steps to calculate M.F.
  • Given molecular mass, ratio of weights = m.w/mf = whole no.
  • Example: Succiric acid
  • Calculation: C4H6O4
• Balancing Equations:

  • Chemical reactions (Rxn)
  • Chemical change in which one substance is changed into another substance
  • Involves changes in chemical composition of matter and energy changes
  • Chemical equation: Reactants on the left, Products on the right
  • Symbols used in equations: →, +, (s), (l), (g), (aq), catalyst, Escaping gas, Heat, Precipitate, Reversible
• Why do we balance equations?

  • To follow the law of conservation of mass