Chem.1 Final - basic chemistry Flashcards
Quantum numbers
- Principal: id. the shell (distance from the nucleus-K,L,M,N,O…)
- Angular (orbital): id. the subshell (shape of the orbitals belonging to the subshell-s,p,d,f,g…)
- Magnetic: id. the orbital (orientation of the orbitals in magnetic field)
- Spin (projection): the two possible spin of an e-
de Broglie hypothesis
Every object in motion with momentum, p has a wave character. de Broglie wavelength: λ = h/p (h: planck consonant)
Uncertainty principle - W.Heisenberg
The position and momentum of a particle cannot be simultaneously measured with high precision. There is a minimum for the product of the uncertainties of these two measurements.
For the motion and place: ΔpΔr = ħ/2
For the energy and time: ΔEΔt = ħ/2
ħ = h/2(pi) (=1.055 * 10^-34 J*s)
Quantitative aspects of Daltons theory
- Law of conservation of mass: no change in mass in chem.R
- Law of definite proportions: a pure comp. cont. the same elements combined in the same proportions by mass.
- Law of multiple proportions: If A and B form more than one comp., the masses of A, comb. with B, are in a ratio.
Isotopes
Atoms whose nuclei have the same atomic nr, but diff. mass nr –> Diff. neutron nr.
Wave nature of light
A cont. repeating change of oscillation of matter or a physical field in which the oscillation travels.
Mole number
n = N/NA
NA: Avogadro´s nr.-6.022*10^23 mol^-1
Electronegativity
How much E an element has to use to attract e-.
Eg. F=high EN. Na=low EN.
Alfa-particle
Nucleus of helium-4 isotope; ^4He^2+
Postulates of the Rutherford model
- Most of the mass of an atom is conc. in its nucleus.
- Nucleus is pos. charged, of p+ and n.
- Around nucleus move the e-.
- Atomic diameters ca. 105 times larger than of the nuclei.
EM radiation: def. on:
-wavelength
-frequency
Formula of speed of light
Wavelength (λ): dist. betw. two identical points of wave (m)
Frequency (ν): nr. of wavelength that pass a fixed point in one unit of time (1/s = Hz)
Speed of light: c = λ⋅ν (m/s)
Energy of a quantum (photon)
(Planck-equation): E=h⋅ν
h: Planck’s constant (J⋅s)
ν: frequency of radiation (Hz)
Energy of a shell/level
En = − const./n2
Bohr theory
- e- only travel in special orbits: at certain distances from the nucleus with specific E.
- e- of an atom revolve around the nucleus in orbits. These have definite E –> E shells/levels.
- Lowest possible E level=ground state. e- absorbs E and „jumps” to a higher E level –> atom in excited state.
- When e- falls back to a lower level, E will be emitted in form of a quantum of „light” (a photon).
Pauli’s exclusion principle
No two electrons can have the same four quantum numbers in an atom.
Building-up (Aufbau) principle
The subshells are built up in an order as the energy of the subshells increases.
Hund’s rule
The rule of maximum multiplicity, 2S+1. The e- are distributed among the orbitals of a subshell in a way that gives the maximum number of unpaired e- with parallel spins.
Atomic size
The effective size of a single atom cannot be defined. Atomic radius=bond distance/2
Ionizing E
The E required to remove the most loosely held e- from an isolated atom in its ground state=first ionization energy.
A(g) → A+(g) + e−
Electron affinity
The E change (∆E) associated with the process in which an e- is added to a gaseous atom in its ground state.
A(g) + e− → A−(g)
Polar covalent bond/Nonpolar covalent bonds/Ionic bonds
- Polar: has greater e- density around one of the atoms. Bonding e- shared unequally. Partial charges. E.g.H2O
- Nonpolar: Bonding e- shared equally. No charges. E.g.CH4 and H2.
- Ionic: Complete transfer of one or more valence e-. Full charges on resulting ions. E.g.NaCl.
Coulombs law
Gives the electric force between the two point charges. F=k(q1q2)/r^2 k: Coulombs constant q1 and q2: point charges r: dist. betw. the two point charges
Electric dipole moment
A vector quantity (measure of net molecular polarity). Hence it can be broken down into a vertical and horizontal comp.
Intermolecular Interactions
1) Dipole-dipole (Methanol+chloroform)
2) Dipole-induced dipole (Cl-+hexane)
3) Dispersion-Van der Waals (octane and hexane)
4) H-bond (Methanol and H2O)
5) Ion-dipole (Na and H2O)
6) Ion-induced dipole (Acetone and hexane)
Ionic bonding
Involves the electrostatic attraction between oppositely charged ions.
Lattice energy
The E required to convert the crystal into infinitely sep. gaseous ions, in vacuum (endothermic proc.). Unit: kJ/mol.
Molecular orbit theory (interference, additive/substractive comb. and bonding/antibonding orbitals)
(Gives the probability of finding an e- in certain regions of a mol.)
- Interference: comb. of two (or more) waves
- Additive comb.: same wavelength and same phase; reinforcement of in-phase waves
- Subtractive combination: same wavelength and opposite phase; cancellation of out-of-phase waves
- Bonding orbitals: Addition of atomic orbitals. Mol. orbitals that are conc. in regions betw. nuclei (i.e. prob. density of e- is not zero between the nuclei).
- Antibonding orbitals: Subtraction of atomic orbitals. Mol. orbitals having nodal plane betw. nuclei (i.e. prob. density of e- is zero between the nuclei).
Multicenter (Delocalized) Bonding
Several Lewis structures are used together, because none of them exactly represents the actual structure. To represent the intermediate, a resonance hybrid is used instead.
Hybridization Theory
- To explain the bonding scheme in a molecule.
- The mixing of at least two non-equivalent atomic orbitals.
- Requires an input of E. The system recovers this E during bond formation.
- Covalent bonds are formed by the overlap of hybrid orbitals or of hybrid orbitals with unhybridized ones.
Electron-pair repulsions and molecular geometry
The valence e- pairs surrounding an atom mutually repel each other, and will therefore adopt an arrangement that minimizes this repulsion, thus determining the molecular geometry –> as far apart as possible.
Primary bond types
- Covalent bond:
- Covalent molecular (e.g.H2O, NH3)
- Covalent network (e.g. diamond SiO2) - Ionic bond (e.g. NaCl)
- Metallic bond (e.g. Cu)
Kinetics
The area of physical chemistry concerned with
- the velocity (or rate) at which a chem. R occurs
- the investigation of the reaction mechanisms
Reaction rate
Change in amount/conc. (at const. V) of a reactant or prod. in a given unit of time
Temp. dependence of R rates-Collision theory
Collisions betw. the reactant mol. are required.
- Effective collision: prod. chem. new substance(s)
- Ineffective collision: the mol. rebound unchanged (elastic collision)
Activated complex
A collection of intermediate structures in a chem. R that persist while bonds are breaking and new bonds are forming. Not a defined state.
Classification of R according to their mechanisms
Multistep:
- Singlestep:
- -Unimolecular (CH3NC –> CH3CN)
- -Bimolecular (CH3Br + OH- –> CH3OH + Br+)
- -Termolecular (very rare, A + B + C –> prod.)
Catalyst
A substance that increases the rate of a chem. R without being used up in the R.
-lowers the Ea
-opens a new path where the R can take place
Homogeneous and heterogeneous catalysis.
Autocatalyst
The R. is accelerated by one of the R. prod. The catalyst forms in the course of the R.
Inhibitors and catalytic poison
Inhibitor: „Neg. catalysts”; increases the Ea. (E.g. antioxidants retard the decomp. of foods by oxidants).
Catalytic poison: Substance that inhibits the activity of a catalyst by blocking its „active site”
Chemical Equilibrium
Reversible R that can proceed in both directions.
Homogenous and heterogenous (same/diff phase)
Equilibrium constant and temp.
If the temp. is raised of a:
- Exothermic R: shifts to the left
- Endothermic R: shifts to the right
The Arrhenius Concept
Acid: a comp. that prod. H+ ions in water
Base: a comp. that prod. OH- ions in water
The Brønsted-Lowry Concept
Acid, BH: a comp. that can donate a proton (proton donor)
Base, B: a comp. that can accept a proton (proton acceptor)
- Amphiprotic
2. Ampholytic
- Substances that can function as acids or bases. E.g.H2O
2. Both H-atom and neg. charge. Acts as both acid and base. E.g. HCO3-.
Electrolytes in aqueous solution
- Strong electrolytes: complete ionization-complete dissociation (e.g. KCl, HBr, NaOH)
- Weak electrolytes: incomplete ionization-incomplete dissociation (e.g. HgCl2, CH3COOH, NH3)
Buffer solution
Is capable of maintaining its pH at nearly constant value even when small amounts of strong acid/base are added.
Composition of buffers
1.Weak acid+its salt (with a strong base) (e.g.CH3COOH+CH3COONa)
2.Weak base+its salt (with a strong acid) (e.g.NH3+NH4Cl)
Generally: a weak acid and its conjugated base are both present in the buffer solution.
Polyprotic acids
Contain more than one acid hydrogen per molecule. E.g. H2SO4, H3PO4 and oxalic acid.
Acid-base indicators
Organic comp. of complex structures that change colour in sol. when pH changes.
Titration
One of the methods of quantitative chem. analysis, where a standard sol. is R with a sol. of unknown conc. in order to determine it´s conc.
Structure of peptides and proteins
- Primary: sequence
- Secondary: regularities in the conformation of the polypeptide chains determined by the H-bonds betw. the >C=O and H-N
- Tertiary: stabilized by the H-/dispersion-/disulfide bonds betw. R-groups. The 3-D shape of the whole mol.
- Quaternary: how several protein molecules come together to yield large aggregate structures.
Classification of proteins
- Building proteins:
1. Simple proteins: comp. of chains of amino acids
2. Conjugated proteins: chains of amino acids+non-protein part - Shape of the amino acid: Fibrous or globular proteins
Detection of proteins
- Irreversible coagulation(denaturation): conc.acids(e.g.HCl)
- Reversible coagulation: conc. sol. of alkali and ammonium salts (e.g.[NaCl, (NH4)2SO4])
- Xanthoproteic-test: cc.HNO3, yellow colour
- Millon-test: HNO2, Hg(NO3)2, Hg2(NO3)2, red ppt.
- Biuret-test: CuSO4/NaOH, Cu(II)-protein(amide) complex
- Pauly-test: diazotized sulphanilic acid, orange colour
- Sakaguchi-test: naphthol, brown colour
- Ninhydrin-test: deep blue/purple
Carbohydrates classification
1.Monosaccharides: (simple carbohydrates, simple sugars). E.g. ribose, glucose, fructose
2.Oligosaccharides: 2–6 simple carbohydrate units. E.g. cane sugar, milk sugar
3.Polysaccharides: macromolecular natural products.
E.g. starch, glycogen, cellulose
Monosaccharides
- Consists of?
- Pos/neg Fehling?
- Examples
- Some OH-groups (polyalcohols) and one aldehyd/keton group
- Pos. Fehling
- E.g. glucose, fructose, ribose, vitamin C
Classification of monosaccharides
- Aldoses/Ketoses
- Nr. of C-atoms (C3: trio-, tetro-, pento-, hexo-)
- D/L (last hydroxyl group on the right/left)
- Alfa/Beta (OH down/up)
Furanoses and pyranoses
Cyclic structures containg 5 and 6 C-atoms.
Mutarotation
Cont. change of optical rotation until it finally settles down to a constant value.
Anomers
Isomeric α and ß forms which have id. configurations except for their diff. at the chiral center on C-1 atom
Constitutional isomers
Mol. having same mol. formula, but diff. order of atomic connections.
Compounds that do not follow octett rule
NO, BH3, BF3
Deoxy sugars, amino sugars
- Deoxy sugar: An OH group is replaced by a H atom
- Amino sugar: - - - by an NH2 group
Detection of monosaccharides
- Tollens(silver mirror test): Detects aldehyde/ketone with [Ag(NH3)2]. Ag ppt.
- Fehling: Detects aldehyde/ketone with Cu2+. Red ppt. (CuSO4, K, Na-tartrate, NaOH Cu2O).
- Nylander: Detects reducing sugars. Sol. of a bismuth-salt Bi. Black ppt.
Disaccharides
- Consists of?
- Pos/neg Fehling? -examples?
- Two monosaccharides joined together by O-glycosidic link
- Pos. Fehling: Reducing disaccharides (free glycosidic OH-group (acetal) and mutarotation). E.g. lactose, maltose and cellobiose
- Non-reducing: Sucrose
Polysaccharides
- Consists of?
- Examples?
- Large number (100-1000) of monosaccharides joined together by acetal-like bonds (glycosidic coupling).
- E.g. starch
Types of H.C
- Saturated (open chain/cyclic)
- Unsaturated (open chain/cyclic)
- Aromatic
Cyclodextrins
Comp. of five or more alfa-D-glucopyranoside units linked alfa(1,4) as in amylose. Interior part forms a host-guest
complex with hydrophobic mol.
Derivatives of cellulose
- Carboxymethylcellulose (CMC): -CH2OCH2COONa groups
- Cellulose nitrate
Markovnikov´s rule
When an unsymmetrical substituted alkene reacts with a H halide, the H adds to the C that has greater nr. of H-substituents.
Aromatic H.C.
Derivates of benzene, with particular el. structure-flavour properties (=Arenes). Parent compound: benzene, C6H6
Conformation
Specific arrangment of atoms within a mol., emerging from the free rotation around the C-single bonds.
Isomers differ only in rotation around a single bond.
Can not be isolated.
Electron-configuration
- Shells: K, L, M, N
- Subshells: S, P, D, F
- 4S is before 3D
- S: 1 orbital, P:3, D:5, F:7
- The last e- in the last subshell, belongs to this block in the periodic table.
Lewis acid/base, with examples
Acid: Mol./cons. that form a covalent bond by accepting e- pair. Central cation, oxidant, cathode, e- withdrawing/-poor, electrophilic. E.g. trifluoride, H+, Al3+, CO2, Cu2+
Base: Mol./cons. that have unshared e-pair(s). Ligand, e-donor, reductant, anode, electron donating/-rich, nucleophilic. E.g. NH4+, H2O, OH-
Le Chatelier´s principal
A system in equilibrium reacts to a change (stress) in conditions in a way that counteracts the applied change and establishes a new equilibrium state.
- Conc.: incr.->opposite/decr.->same
- Pressure: incr.->least mol./decr.->most mol.
- Temp.: incr.->endotherm.R/decr.->exotherm.R
Lipids
Naturally occurring organic substances isolated from cells and tissues by extraction with nonpolar organic solvents.
Cracking
Transformation of high boiling hydrocarbons into simpler hydrocarbons of shorter carbon chain
Stereoisomeri
Isomers that differ in 3D-arrangement of their atoms
Chrical/achiral molecule
Chiral: A mol. that is not superimposable on its mirror image.
Achiral: A mol. that is superimposable on its mirror image.
Enantiomers
They are stereoisomers differing only in the 3D-arrangement of substituents. Are mirror images that are not superimposable.
Optical activity
The abiliity of a substance to rotate of the plane of polarized light
Diastereomers
Stereoisomers, that are not mirror image isomers. Generally:
- at least one chiral center should have the same configuration
- at least one chiral center should have the opposite configuration
Bond order
nb: nr of the bonding e-
nab: nr. of the antibonding e-
(nb + nab = nr. of e- in the mol.)
Derivatives of carboxylic acids
Derived by transformations in the -COOH group.
Acyl halides, esters, amides and anhydrides.
