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Analytical Chemistry > Complexometry ✅ > Flashcards

Complexometry ✅ Flashcards

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1
Q

What is complexometry?

A

volumetric analytic method based on titration of metal ion solutions with a substance that, combined with metal ions, yields complex compounds.

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2
Q

Are complex compounds coloured?

A

some are, yet complex compounds do not have to be coloured.

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3
Q

What changes occur during the formation of complexes?

A

No visible changes, no changes in properties, no precipitate, no colour change.

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4
Q

What is the structure of complex compounds?

A
  • central metal atom
  • surrounded by ions/molecules called ligands

ligand: electron donor

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5
Q

What is a complex compound called when it is charged?

A

a complex ion

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6
Q

What are ligands?

A
  • typically anions or polar molecules.
  • must have line pairs of electrons to interact with metals.
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7
Q

What do coordinate covalent bonds need?

A

a donor atom (which donated electrons)

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8
Q

What does the number of electron pairs a metal ion is capable of recieving depends on?

A
  • its radius
  • electron configuration
  • structure of the ligand
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9
Q

What is a coordination number?

A

the number of atoms or ions immediately surrounding a central atom in a complex or crystal.

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10
Q

What is coordination?

A

When an orbital from a ligand with lone pairs in it overlaps with an empty orbital from a metal.

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11
Q

When is the complex most stable?

A

In its symmetrical structure.

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12
Q

How is a metal-ligand bond formed?

A

between a lewis acid and lewis base

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13
Q

What lewis is a metal?

A

lewis acid (accepts electrons)

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14
Q

What lewis is a ligand?

A

lewis base (donates electrons)

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15
Q

What is a mixed complex?

A

more than one type of ligand present in a complex

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16
Q

What are multi-center complexes?

A

complexes with 2+ central metal ions.

17
Q

In coordination compounds, what type of valency do central metal atoms exhibit?

A
  • primary valency (oxidation state)
  • secondary valency (coordination number)
18
Q

What is a monodentate complex?

A

If there is only one donor atom in the ligand.

19
Q

What is a bidentate complex?

A

If there are two donor atom in the ligand.

20
Q

What valency do all metal atoms have fixed?

A

number of secondary valencies

21
Q

Why do compounds have definite geometry?

A

The coordination number of secondary valencies is always directed towards fixed positions in space.

22
Q

What is A, B, and C?
A[B(C)x]

A

A- second coordination sphere
B- central metal ion
C- ligand
x- coordination number
[B(C)]- first coordination sphere
A- second coordination sphere

23
Q

When is the formula of [complex ions (primary coordination sphere)] put before the secondary coordination sphere? When after?

A

before: if the [] is positive
after: if the [] is negative

24
Q

How to name complex compounds?

A

1) coordination number (mono-, di-, tri- and etc.)
2) ligand
3) metal ion with valency state

eg. [Ag(NH3)2]+: diammine-silver (I) ion
[Ni(H20)6]2+:hexaaqua-nickel (II) ion

25
Q

How to name complex anions?

A

1) coordination number (mono-, di-, tri- and etc.)
2) ligand
3) metal ion with valency state, **add “-ATE” to metal **

eg. [Al(OH)4]: tetrahydroxo-aluminate (III) ion
[Cu(NH3)4]SO4: [tetraamine-copper (II)]- sulphate

26
Q

What is a complexone? What is a complexonate?

A
  • any chylating agent used for the analytical determination of metals.
  • form stable complex compounds with numerous ions of metals
27
Q

What is a chelating agent?

A

organic compounds which complex metal ions.
- removes a metallic ion from a solid salt and holds it in solution.

(catch ions to stabilize the system)

28
Q

What is a common complexonate? What is it most commonly used for?

A

EDTA
- determining of water hardness

water hardness: Mg 2+ and Ca2+

29
Q

What are the two types of metal hardnesses?

A

1) temporary (carbonate hardness)
2) permanent (non-carbonate hardness)

30
Q

What is temporary hardness?

A

casued by Ca(HCO3)2 and Mg(HCO3)2

31
Q

What is permanent hardness?

A

caused by Ca2+/Mg2+ sulfates, chlorides, silicates, -phosphates and nitrates.

32
Q

What is “water softening”?

A

The elimination of calcium and magnesium salts from water.

33
Q

Water hardness titration.

A

indicator: eriochrome black T
colour change: red (chelated) –> blue (not chelated)

34
Q

How can temporary hardness be eliminated?

A

by water boiling

CaCO3 precipitates, but has to be removed or it will dissolve again.

35
Q

How can permanent water hardness be removed?

A
  • not by boiling!
  • slacked lime
  • soda
  • sodium phosphate
  • borax
  • exchangers (ionites): SODIUM AND HYDROGEN CATIONITES

Analytical Chemistry (12 decks)

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