Language of Chemistry w/Prof. O. Corcoran
Chem-studies matter and changes it undergoes. Atoms-building blocks of matter. Molecules-2+
atoms. Element-same kind of atoms. Homogenous-all atoms are the same. Pure compound-every
molecule has the same elements; distinct properties and unchanging composition. Element-no
simpler substances. Compound-contains 2+ elements, 2+ atoms. Mixture-2+ substances where
each has own chemistry identity and can be separated from each other. Hetero=not same
composition, properties, and appearance thrioughout. Homo=vanilla ice cream, uniform
throughout. Property-characteristic to recognize types of matter and distinguish it from other
types. Atoms within-composition; arrangement of atoms-structure. Physical-observed without
changing a sub into another (diff in BP, density, m, V). Chemical-only observed when sub is
changed into another-flammability, corrosiveness (RA form). Intensive-independent of amount
of substance (density, BP); extensive-dependent (m, V, E). Ethylene glycol-antifreeze.
CHONSP=most common in living organisms-nonmetals. Atomic number-e’ in the outermost
shell. Memorize first 20 elements. Mass/Metre=m. K=C+273.15
Units-g, m, s, K, mol, A (amperage for electric), cd (candela-luminous intensity). 37 is core body
temp of human (310K). Calculations=done in calculator. Otherwise, conversion.
Density=rho (ρ). Go as far as 2 decimal places. Look at decimal places in problem. Accuracy-vs
true value of a quantity. Precision-proximity of several measurements to each other.
Atoms, Molecules, and Stoichiometry
Atoms-central nucleus surrounded by orbiting electrons. Atomic #=proton number, proton # is
same. Relative mass=1 for proton, neutron, electron is basically 0 (energy not really a mass).
Mass # on top (p+n), atomic on bottom. Element characteristic is proton #, can change neutron
#-isotopes. C11, PET-radioactive element-find cancer.
Molecular formula (H2O2) vs structural formula (H-O-O-H). Organic compound-carbon,
hydrogen, oxygen, nitrogen. Inorganic-metal first.
Stoich-Lavoisier Law-Mass in isolated/closed system not create/destroy by chem reactions/phys
transform. In stioch-equal # of atoms. Reaction types: combination, decomposition, combustion
(rapid, produce a flame, makes CO2 and H2O), (redox and double replacement maybe later).
Molecular weight=Mw. Relative atomic mass=Ar-average of all isotopes considering natural
abundance. Avogadro number: 6.022*10^23=1 mol. Ar=mass of 1 mol of element.
Molar mass=Mr=mass (g) of one mol of sub (times this by 2 if O2). Carbon is reference element.
Ar=16 for Oxygen, so 16g of Oxygen contains 6.022*10^23 atoms. So 16g of oxygen is weight
of a mol of oxygen. Atomic/molar mass=g/mol units. Molar mass=Mw numerically. There is
atomic oxygen (just 16) and Mw is 32 (x2, same with number of atoms-but not molecules).
Mw=formula mass, but molar mass is accurate. Mr=g/mol. Moles=mass (g)/molar mass (g/mol).
Writing: _ moles of _ react with _ moles of _ to form _ moles of _. Ratio=coefficients.
Homogenous mixtures of 2+ pure substances, solvent: greatest abundance, everything
else-solutes (l or s); both make a solution when mixed-clear liquid for homo (juice-suspended,
heterogenous). Solutes-electrolyte (dissociate into ions in H2O-salt-ionic bonds).
, Nonelectrolyte-dissolve in water, but stays as
is (sugar-molecules). Concentration words:
diluted, concentrated, saturated. More solute
dissolved in one amount of solvent, greater
concentrated. Molarity of a solution (M)
=moles of solute/volume of solution (L).
M=mol/L.
Dilutions=C1V1=C2V2
because moles=moles.
Mass-mass percent conc: (mass of solute/(mass of solute + mass of solvent))*100. All in grams.
Mass-volume percent conc: (mass of solute (g)/volume of solvent (mL))*100.
Volume-volume percent conc: (volume of solute/(volume of solute + volume of solvent))*100
All in mL. Dilutions-reducing the concentration for further analysis. Stock solution-concentrated
solution that will be diluted (save prep time, conserve material, improve accuracy). Add solvent
to dilute it (solvent-abundant, solute-smaller amounts). Water-polar (H bond) so is universal
solvent. Moles of solute remains the same. Doubling dilutions (2x dilutions) used in serological
assays. Concentration is half as the one before. MIC-minimum inhibitory concentration (lowest
conc of antimicrobial inhibiting growth of an organism.
(Water & pH of) Acids and Bases
Solution-homo mix of 2+ pure subs. Water-most versatile solvent-polarity (2 lone pairs of
electrons). Bent shape, not linear. O more electroneg than water. Partial neg charge (dipole).
Localisation of e’ in one part, then a delta plus on opp. Neg<-|-pos. Hydrogen bond-NOF.
Intermolecular forces-h bond, dipole^2, dispersion (strongest to weakest). Not a gas because of
the H bond (is light, ect so expect to be a gas). DNA, proteins, stick together because of H bond.
Intramolecular H bond-on a seq of amino acid, protein folds to make a protein tertiary structure.
Filament-protein no perform. Intermolecular-like DNA. Solute types: electrolyte-ions dissociate
readily in polar solvent like salt-and non-electrolyte-organic compounds (can soluble in water,
but stay as is-sugar). O goes to pos ion, H2 goes to neg ion. Neutral-highly stable. Forms a
hydration shell. Nonionic but polar-can dissolve in water (H12C6O6) all of the OHs can H bond
to water. Like dissolves like. Strong electrolyte dissociates completely, weak only partially
(double arrow). Acid-DONATES a proton; Bronsted-Lowry acid must have a removable (acidic)
proton. Base-accepts a proton-need pair of nonbonding electrons. Some bases produce OH,
which then accept the H (make water). Proton=H+. NaOH-strong-Na+OH, OH+H>H2O.
HCl + H2O→Cl- + H3O+ though. Ammonia+water→ ammonium and OH, N has nonbonding
electron pair so it adds H there. Water is different, acid donates the proton; ammonia base accepts
proton. Stronger acid, weaker conjugate base. High tendency to lose proton, then it is harder to
accept the proton. ACID IS W/H (loses it in process). Equilibrium=Products/Reactants.
, Water=acid or base, depends on situation=amphiprotic (hence universal solvent). Kw is
ion-product constant-Ka times Kb. Kw must be constant or water is no longer neutral (is
always 1*10^-14). Acidic=H>OH. pH=-log[H+]. [H+] is in moles/litre (M). Little p
means -log. pH dec, then H+ inc, solution is more acidic. One pH unit inc=ten fold inc in
[H+]. Acids are lower on the pH scale-zero to 14.
Monoprotic-donate one H; polyprotic-donate more than one H. Smaller pKa-stronger
acid (more [H+]). New formula: [H+]=sqrt(Ka*[HA]). No need to deal with H2SO4
luckily. NH4+ is an acid, NH3 is the conj base.
Titration (our lab)-Allows us to determine conc of unknown by knowing conc of reagent.
Quantitative volumetric analysis. Known conc-standard solution. Reagent-titrant/titrator. Known
reacts with analyte/titrant to determine conc. Volume of titrant used is called titration volume.
Neutralisation reactions-acid and base combine, products are a salt and water-HCl and NaOH.
Aq is all but water (l). This we use with indicator-to see when changed colour SLIGHTLY-which
is the equivalence point. Standard could also be used to calibrate analytical instruments-controls.
Primary standard-extremely pure, stable (low reactivity), no waters of hydration, and high
molecular weight. Ours in lab is secondary-over time is unstable, and must get conc before lab.
Low hygroscopicity-no humidity by the air. Equivalence point-moles of acid=moles of base.
Acid base indicators-dye that changes colour with the pH (acidic-colourless, basic-pink).
pH of Buffers and Redox 24/10/19 Dr. E. Galante
Le Châtelier principal-equilibrium is disturbed by changing
conditions, system moves to counteract the change-homeostasis like.
It does this to get Kc back to where it was (K no change).
For a weak acid (acetate), lies far to the left (not dissociate readily).
For the salt (sodium acetate), far to right (totally dissociate).
Common Ion effect: add corresponding salt (increase ion, not H; add
strong acid to increase H), then shifts to the left. Now you have a
buffered solution-weak conjugate acid/base pair.
Resistant to pH changes-even w/strong acid/base. Acid w/salt of
conj base=buffer.
Henderson-Hasselbalch equation→pH=pKₐ+log([A⁻]/[HA])
This is how to find pH of a buffered solution, because it shows
the relationship between pH and pKa. If mole of acid = mole of
salt, then log([A⁻]/[HA]=0.
