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Z Old Medical Chemistry > Midterm 2: Thermo, Electro, Complexes, Organic > Flashcards

Midterm 2: Thermo, Electro, Complexes, Organic Flashcards

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1
Q

What is a metal complex?

How can it be a complex ion?

A

a central metal atom bonded to a group of molecules or ions

  • is an ion if it has a charge
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2
Q

How is pH determined if concentration and pKa are known?

A

pH = (pKa - log C)/2

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3
Q

How can pH be determine with Ka and concentration?

A

[H+] = √(Ka * C)

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4
Q

What are compounds containing complexes called?

A

coordination compounds

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5
Q

What is a ligand?

What are some usual characterics of ligands?

A

A molecule or ion coordinating to the metal in a complex

  • usually anions or polar molecules
    ex: H20, CN-, Cl-, NH3
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6
Q

What are primary and secondary valences in relation to metal ions?

A

primary - oxi # for the metal

secondary - # of atoms directly bonded to the metal (AKA coordination number)

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7
Q

What is the coordination sphere?

A

the central metal of a complex and all the ligands directly bonded to it

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8
Q

How are complex formulas written?

What do the brackets indicate?

A

Complex formulas are written with brackets around the coordination sphere.

This means that everything outside the brackets dissociate from the complex ion (coordination sphere) when dissolved.

ex: [Co(NH3)6]Cl3would indicate 6 ammonias bonded to the central cobalt and 3 dissociable chloride ions outside the coordination sphere

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9
Q

Describe the metal ligand bond.

How is it a Lewis acid/base situation?

A
  • ligands have non-bonding electrons and thus can donate electrons, or be a lewis base
  • **metals **have empty orbitals and this can accept electrons, or be a lewis acid
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10
Q

What is a donor atom?

A

the atom of a ligand that supplies the non-bonding electrons for the metal-ligand bond

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11
Q

What is a coordination number?

A

the number of donor atoms bonded to the metal of a complex

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12
Q

What are the 2 most common coordination numbers and their most common geometries?

A

4 - tetrahedral or square planar

6 - octahedral (two tetrahedrals one on top of the other)

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13
Q

What is a polydentate ligand?

A

a ligand molecule with two or more donor atoms (atoms attached directly to the metal of the complex)

  • if it has only two it is bidentate
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14
Q

How many donor atoms does EDTA have?

A

6

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15
Q

What is a chelating agent?

A

another name for polydentate ligand

form stable complexes and can therefore chelate (or sequester) metal ions from solution

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16
Q

How are coordination compounds named?

A
  1. Ligands listed alphabetically with numerical prefixes (ignoring prefixes in alphabetization) before metal name (ex: Dibromo-, Pentaammine-)
  2. Anionic ligand names always end in -o (ex: bromo, chloro, fluoro)
  3. Oxi # of the metal is listed as roman numeral in parentheses after the metal (ex: cobalt(III) )
  4. Anion comes last (ex: chloride, carbonate etc.) but if complex is an anion (more rare) then it comes last and ends in -ate.

Examples:

Pentaamminechlorocobalt(III) Chloride

or

Sodium Tetrachlorooxymolybdate(IV)

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17
Q

What is the first law of thermodynamics?

A

the change in the internal energy of a closed system is equal to the amount of heat supplied to the system, minus the amount of work done by the system on its surroundings

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18
Q

What are reversible and irreversible processes?

A

Reversible - the system changes in such a way that the system and surroundings can be put back in their original states by exactly reversing the process

Irreversible - cannot be undone by exactly reversing the change to the system (all spontaneous processes are irreversible)

  • In irreversible process below, replacing the partition would not create the same two compartments. Work must be done to void the left compartment of gas.
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19
Q

What is entropy? What letter represents it?

A
  • a measure of the randomness of a system
  • related to various modes of motion in molecules
  • represented by S
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20
Q

What is the 2nd law of thermodynamics?

A

The entropy of the universe does not change for reversible processes and increases for spontaneous processes.

(entropy can decrease for individual systems, though)

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21
Q

What are the 3 types of motion in molecules?

A

**translational ** - whole molecule one place to another

**vibrational **- periodic motion of atoms within a molecule

**rotational **- rotation of molecule about an axis or rotation about sigma bonds

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22
Q

What are the three main conditions directly proportional to entropy?

A
  • temperature - measure of avg kinetic energy of molecules in a sample
  • **volume **(w/ gases) - larger volume allows more freedom of movement
  • # of independently moving molecules
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23
Q

What is the third law of thermodynamics?

A

The entropy of a pure crystalline substance at 0 Kelvin is zero.

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24
Q

How are standard entropies and molar mass related?

A

standard entropy tends to increase with molar mass

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25
Q

What is the Gibbs Free Energy equation?

A
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26
Q

For spontaneous processes, what is delta G in the Gibbs free energy equation?

What do other values for delta G mean?

A

delta G is **less than zero **for spont. processes

delta G = 0 - system is at equilibrium

delta G > 0 - non spontaneous, spontaneous in reverse direction

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27
Q

Considering the Gibbs Free energy equation…

if ΔH is positive and ΔS is positive, the reaction is…

A

Spontaneous at high temperatures, non-spontaneous at low temperatures

because ΔH - TΔS will be negative if T is high enough

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28
Q

Considering the Gibbs Free energy equation…

if ΔH is negative and ΔS is negative, then…

A

rxn is spontaneous at low temperatures and non-spontaneous at high temperatures

**- **because ΔH - TΔS is negative if T is low enough

29
Q

Considering the Gibbs Free Energy equation…

if ΔH is positive and ΔS is negative, then…

A

rxn is **non-spontaneous at all temperatures **

because ΔH - TΔS will always be positive

30
Q

Considering the Gibbs Free Energy equation…

if ΔH is negative and ΔS is positive, then…

A

the reaction is spontaneous at all temperatures

  • because ΔH - TΔS will always be negative
31
Q

How are gibbs free energy and equilibrium related in standard state conditions?

A
32
Q

What is a coordinate covalent bond?

A

a bond which forms when a Lewis base donates a pair of electrons to a Lewis acid

33
Q

In a voltaic cell, where does the oxidation occur?

A

the anode because electrons are lost and sent to the cathode as the anode’s metal is oxidized

34
Q

What is the Daniell cell and its voltage?

A

Cu/CuSO4 cathode, Zn/ZnSO4 anode

1.1 V

35
Q

In a voltaic cell, where does the reduction occur?

A

in the cathode, because electrons are received from the anode and cations are reduced to their uncharged form

36
Q

How should the equation for the potential of an electrode be altered when dealing with an anion as the active part of the electrode?

A

the plus in “+ 0.06/z * log C” becomes…

MINUS

37
Q

How is a standard hydrogen electrode formed?

A

A platinum (Pt) plated placed in 1 M HCl with hydrogen (H2) gas pumped into solution

  • has 0 V potential
38
Q

What is the Nernst equation?

A

Eelectrode = E°electrode + 0.06/Z*log C

39
Q

In a concentration cell, what makes the cathode positive and anode negative?

A

the cathode has a higher concentration of solution (and thus higher concentration of cations)

(except maybe with a cell run on negative ions???)

40
Q

What is the equation for the electromotive force of a concentration cell?

A

Emf = 0.06/Z * log Ccathode/Canode

41
Q

What is the equation for the electromotive force of a concentration cell based on H+ if the pH of its anode and cathode are given, or calculable?

A

Emf = 0.06(pHanode - pHcathode)

42
Q

Explain a redox electrode.

A

A redox electrode contains both oxidized and reduced forms of the relevant cation in solution.

The oxidized form (ex: Fe2+) gives off an electron to the metal plate in the solution (ex: Pt) and thus the reduced form (ex: Fe3+) is created.

43
Q

What is the Nernst equation for a redox electrode?

A

Eelectrode = E°electrode + (0.06/Z)*log(Cox/Cred)

44
Q

Explain a non-polarized electrode.

A
45
Q

What is the formula for reaction heat/enthalpy change?

A

ΔHrxn = ΣΔHproducts - ΣΔHreactants

46
Q

How should molecules such as O2(g) or H2(g) be treated when calculating reaction enthalpy changes?

A

They are left out because by definition their formation heat is zero.

An element in its usual molecular form has no formation heat.

47
Q

Define endergonic.

A

an endergonic reaction absorbs energy in the form of work

an endergonic reaction is therefore non-spontaneous

48
Q

Define exergonic.

A

exergonic reactions give off energy to their surroundings

exergonic processes are spontaneous

49
Q

What is Hess’ law?

A

the change in enthalpy for any chemical reaction is the same whether the reaction occurs in one or several steps

50
Q

When all molecules in a reaction are gases at constant temperature and pressure and there is no difference in # of molecules between reactants and products, what is the relationship between reaction heat and spontaneity?

A

Because these conditions mean there is no change in entropy, according to the Gibbs Free Energy equation, ΔG = ΔH so…

Negative reaction heat (exothermic) is spontaneous

Positive reaction heat (endothermic) is non-spontaneous

51
Q

What is the equation that relates Gibbs free energy to the equilibrium constant (K) of a chemical reaction ?

A

ΔG = -5.7 log K

this produces an answer in kJ/mole

(based on ΔG = RT ln K)

52
Q

How is an alkane named?

A
53
Q

generic chemical formula for alkanes

A

CnH2n+2

54
Q

Rules for Branched Chain Alkane Naming

A
  1. Use longest possible parent chain
  2. Number the longest chain beginning with the end nearest a substituent
  3. Use these numbers to designate the location of the substituents
  4. When two or more substituents are present, give each a number corresponding to its location and list substituent groups alphabetically, ignoring multiplying prefixes (di-, tri-, etc.)
  5. Use same number twice if two substituents are on same carbon
  6. When two or more substituents are identical indicate using prefixes di-, tri-, tetra-, etc.
  7. When two chains of equal length compete for parent chain, pick one with most substituents
  8. When branching occurs at equal distance from end of longest chain choose name that gives lower number at first point of difference
55
Q

What is the typical reaction for an alkane?

A

“radical” substitution of an H atom

56
Q

How are alkenes named?

A

With the same prefixes as alkanes and -ene as a suffix.

With butene and beyond, a number is assigned to the location of the double bond.

ex: 1-butene if the bond is on the side, 2-butene if it’s in the middle

57
Q

prefix for six carbons

A

Hex-

58
Q

prefix for seven carbons

A

Hept-

59
Q

prefix for nine carbons

A

Non-

60
Q

prefix for 11 carbons

A

Undec-

61
Q

prefix for 12 carbons

A

Dodec-

62
Q

prefix for 13 carbons

A

Tridec-

63
Q

prefix for 14 carbons

A

Tetradec-

64
Q

prefix for 16 carbons

A

Hexadec-

65
Q

prefix for 17 carbons

A

Heptadec-

66
Q

Prefix for 20 carbons

A

Eicos-

67
Q

What are the three types of isomers?

A

constiutional - different atom attachment

conformational - bond rotation (Newman projections, chair/boat, etc.)

configurational - stereoisomers

68
Q

What was the 1st known chiral molecule?

A

glyceraldehyde

69
Q
A

Z Old Medical Chemistry (9 decks)

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