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AnaChem MIDTERMS EXAM > AnaChem Exam Post Lab Discussion - Midterms > Flashcards

AnaChem Exam Post Lab Discussion - Midterms Flashcards

1
Q

Classification of titration based on the type of
reaction involved:

A
  1. Acid-base titration
  2. Redox Titration
  3. Precipitation Titration
  4. Complexometric Titration
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2
Q

It involves Acid-Base reaction

A

Acid-Base Titration

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3
Q

Involves ___________; electron transfer

A

Redox Reaction

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4
Q

Involves formation of precipitate

A

Precipitation Titration

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5
Q
  • Involves metal-ligand
  • Formation of colored complex
A

Complexometric Titration

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6
Q

A technique where a solution of known concentration (titration) is used to determine to the unknown concentration of an identified analyte.

A

Titration

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7
Q

Involves addition of solution of known concentration from burette to the measured volume of analyte.

A

Titration

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8
Q

The solution of unknown concentration
( But known volume)

A

Analyte

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9
Q

The solution of known concentration (volume obtained by titration)

A

Titrant

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10
Q

The point at which the moles of added titrant is stoichiometrically equal to the moles of analyte.

A

Equivalence point

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11
Q

Signals the end of titration where in the indicator gives an observable change like sharp color change; located very close to the equivalence point

A

Endpoint

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12
Q

A ______ is slowly added to another until the reaction between the two is complete.

A

Solution

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13
Q

Experiment 5 Title:

A

Determination of Ascorbic Acid in Vitamin C Tablets by Acid-Base Titration.

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14
Q

Bronsted-Lowry Acids

A

Proton/H+ Donor

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15
Q

Bronsted-Lowry Base

A

Proton/H+ Acceptor

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16
Q

It completely dissociates with water

A

Strong Acid/Base

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17
Q

It partially dissociates with water.

A

Weak Acid/Base

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18
Q

H2SO4, HCl, HBr, HI, HNO3, HClO4

A

Common Strong Acid

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19
Q

NaOH, KOH, LiOH

A

Common Strong Base

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20
Q

CH3COOH, HF, H3PO4, HSO4-

A

Common Weak Acid

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21
Q

NH3, Pyridine, Methylamine

A

Common Weak Base

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22
Q

A procedure used in quantitative analysis to determine the concentration of either acid or base.

A

Acid-Base Titration

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23
Q

It should change sharply at the equivalence point.

A

Indicator

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24
Q

At the end point of the titration, all acids/bases are neutralized with acid/based, the flash contains _______ and ________ only.

A

Water
Salt

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25
Q

It is weak organics acids or bases that dissociates slightly in aqueous solutions to form ions.

A

Acid Base TIndicator

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26
Q

It changes colors because their ions have colors that are different from undissociated molecule.

A

Indicators

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27
Q

A commonly used indicator for acid-base titrations and is a weak acid.

A

Phenolphthalein

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28
Q

The weak acid is ______ and its conjugate base is _____

A

Colorless
Pink

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29
Q

Adding _______ shifts the position of euqilibrium to te left, and turns the indicator _________

A

H+
Colorless

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30
Q

Adding ____ removes the H+ shifts the equilibrium to the right, and turns the indicator ______

A

Pink

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31
Q

Titrant:

A

Standardized NaOH Solution

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32
Q

Analyte

A

Ascorbic Acid, HC6H7O6

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33
Q

Indicator

A

Phenolphhalein
(Colorless in acidic and neutral solutions pink in basic solution)

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34
Q

Endpoint

A

Faint Pink

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35
Q

3 acid-base reactions involved:

A
  1. Standardization of Dilute NaOH
  2. Standardization of Dilute of HCl
  3. Titration of Ascorbic Acid in Vitamin C Tablet with NaoH
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36
Q

HC8H4O4K (aq) + NaOH(aq) → KNaC8H4O4
(aq) + H2O(l)

A
  1. Standardization of Dilute NaOH
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37
Q

NaOH (aq) + HCl (aq) → NaCl(aq) + H2O(l)

A
  1. Standardization of Dilute HCl
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38
Q

HC6H7O6 (aq) + NaOH (aq) → NaC6H7O6
(aq) + H2O(l)

A
  1. Titration of Ascorbic Acid in Vitamin C Tablet with NaOH
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39
Q

An important water-soluble biological antioxidant and free radical scavenger.

A

Ascorbic Acid
Vitamin C

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40
Q

It is required for the growth and repair of the tissues in all parts of the body.

A

Vitamin c

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41
Q

An important protein used to make skin, scar tissue, tendons, ligaments, and blood vessels.

A

Collagen

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42
Q

It is sensitive to heat and light and usually available in 500mg

A

Vitamin C

43
Q

Alternative technique to direct titration and designed to resolve some roblems encounted in direct titration like slow titration.

A

Back-Titration

44
Q

A known quantity of ____ is added, greater than the amount required to completely neutralize the ______.

A

NaOH
ascorbic acid

45
Q

_____ and _______ react completely

A

NaOH
Ascorbic Acid

46
Q

The excess _______ is titrated with ________ back to the endpoint.

A

Excess NaOH
Standard HCI Acid

47
Q

The amount consumed in the reaction of back titration is obtained:

A

molesNaOH reacted = molestotal excess NaOH – molesHCl

48
Q

The _____ that reacted is related to the ________ (ascorbic acid).

A

amount of NaOH
amount of the analyte

49
Q

Vol NaOH used 🡺 should be total volume not only excess ________

A

5 mL

50
Q

For direct titration:

A

mass = MNaOH x VNaOH x molar mass ascorbic acid

51
Q

For back titration:

A

mass = [(Mexcess NaOH x Vexcess NaOH) – (MHCl x VHCl)] x molar mass ascorbic acid

52
Q

A mild reducing agent and can be determined with the help of a moderate oxidizing agent like iodine in a direct titration with it.

A

Vitamin C

53
Q

It involves species which undergo reduction-oxidation reaction.

A

Redox Titrations

54
Q

Two common titration methods (involving I2) based on redox reaction:

A

Iodimetry and Iodometry

55
Q

Free iodine (I2) is used to titrate a reducing agent; used to quantify a reducing agent.

A

Iodimetry

56
Q

Iodide (I-) is added that reacts to form iodine (I2), which is then titrated; used to quantify an oxidizing agent.

A

Iodometry

57
Q

The two reactions involved in this experiment:

A
  1. Generation of I2
  2. Oxidation of Vitamin C
58
Q

IO3 − + 6H+ + 5I − → 3I2 + 3H2O

A

Generation of I2

59
Q

C6H8O6 + I2 → C6H6O6 + 2I− + 2H+

A

Oxidation of Vitamic C

60
Q

KIO3 solution more stable than I2 as a ___________

A

Primary standard

61
Q

I2 + 2e - 2I-

A

Reduction of I2

62
Q

Ascorbic Acid <=> Dehydroascorbic Acid

A

Oxidation of Erythorbic acid (C6H8O6)

63
Q

A type of direct titration, the reducing agent has to be an analyte.

A

Iodimetry

64
Q

A technique that involves titrating free iodine with a reducing agent.

A

Iodimetry

65
Q

A technique that involves titrating free iodine with a reducing agent. As a result, iodine decreases to iodide and oxidizes other species.

A

Iodimetry

66
Q

An indirect titration method in which the amount of iodine used in measured, which was used prior to the redox titration, through the means of a separate titration.

A

Iodometry

67
Q

Iodometry Titrant:

A

Standard Thiosulfate Solution

68
Q

Iodometry Indicator:

A

Starch

69
Q

Iodometry Endpoint:

A

Disapperance of Dark-blue color; from intense blue-black to colorless

70
Q

A known excess of iodine is generated in situ by the reaction of known amount of _________ with an excess of _______ in presence of strong acid.

A

Potassium Iodate
Potassium Iodide

71
Q

a titration in which the reducing agent is utilized to titrate the iodine formed in the preceding redox reaction

A

Iodometry

72
Q

a titration in which the reducing agent is used to titrate the iodine solution directly.

A

iodimetry

73
Q

a method of indirect analysis

A

Iodometry

74
Q

iodimetry only requires one.

A

iodimetry

75
Q

involves two redox reactions

A

Iodometry

76
Q

a form of direct analysis.

A

iodimetry

77
Q

only requires one.

A

iodimetry

78
Q

the iodine is oxidized first and subsequently reduced by the reducing agent

A

Iodometry

79
Q

used in many experiments

A

Iodometry

80
Q

the iodine is instantaneously reduced.

A

iodimetry

81
Q

titrations are used less frequently.

A

iodimetric

82
Q

Quantifying oxidizing compounds is done

A

iodometry

83
Q

Quantifying reducing agents is done

A

Iodimetry

84
Q

Titrant:
Analyte: Ascorbic Acid
Indicator: Starch
Endpoint:

A

Titrant: KIO3 Solution
Endpoint: Blue-Black

85
Q

Title of Experiment 6

A

Determinaton of Ascorbic Acid by Iodimetry

86
Q

Title of Experiment 7

A

Determination of Chloride and Sulfate by Precipitation Titration

87
Q

A type of titration that involves the formation of precipitate

A

Precipitation Titration

88
Q

It is based in the production of precipitation at the end point of the titrimetric analysis.

A

Precipitation Titration

89
Q

The titrant and analyte combine to create a precipitate, an insoluble material. it continue until all of the analytes have been consumed.

A

Precipitation Titration

90
Q

Precipitation Titration

Examples of such titrations are often limited to those involving the precipitation of silver ions with anions like ________ or __________

A

Halogens or Thiocyanate (SCN-)

91
Q

The lack of appropriate ____ is one reason for the limited application of such reactions.

A

Indicator

92
Q

Sometimes the response rate is too low, especially when titrating dilute solutions.

A

Precipitation Titration

93
Q

Once the__________ is approached and the titrant is gradually added, a high degree of supersaturation does not occur and the precipitation rate may be quite slow.

A

equivalency point

94
Q

▪ The concentration of the chloride ion present in the unknown solution can be determined by titrating with a solution of a known concentration of silver nitrate.

A

Determination of Unknown Cl-

95
Q

Determination of Unknown Cl-

In this titration, silver chloride precipitates out as a____________-.

A

White Substance

96
Q

Determination of Unknown Cl-

AgNO3 + Cl– →

A

AgCl↓ + NO3–

97
Q

Mohr’s Method of Precipitation Titration

uses _____ as the titrant (burette) and a small quantity of __________ as the indicator to determine the concentration of chloride in a given sample.

A

AgNO3
potassium chromate (K2CrO4)

98
Q

it has a much lower Ksp value in theory it should precipitate first

A
  • silver chromate
99
Q

uses a small quantity of K2Cr2O4 such that the chloride concentration is much higher than that of chromate. This causes AgCl to preferentially precipitate.

A

Mohr’s method

100
Q

When all chloride ions in a given sample has all been converted to AgCl, additional AgNO3 reacts with yellow K2CrO4(indicator) to produce ______________.

A

reddish brown precipitate Ag2CrO4

101
Q

Endpoint is reached when the reddish brown colour remains ‘______’ – does not disappear with stirring.

A

stable

102
Q

Cl– ions are more reactive than CrO42- so the Ag+ ions preferentially react with Cl– ions first to form a__________before reacting with CrO42–.

A

white precipitate

103
Q
A

AnaChem MIDTERMS EXAM (2 decks)

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