AnaChem Exam Post Lab Discussion - Midterms Flashcards
1
Q
Classification of titration based on the type of
reaction involved:
A
- Acid-base titration
- Redox Titration
- Precipitation Titration
- Complexometric Titration
2
Q
It involves Acid-Base reaction
A
Acid-Base Titration
3
Q
Involves ___________; electron transfer
A
Redox Reaction
4
Q
Involves formation of precipitate
A
Precipitation Titration
5
Q
- Involves metal-ligand
- Formation of colored complex
A
Complexometric Titration
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
7
Q
Involves addition of solution of known concentration from burette to the measured volume of analyte.
A
Titration
8
Q
The solution of unknown concentration
( But known volume)
A
Analyte
9
Q
The solution of known concentration (volume obtained by titration)
A
Titrant
10
Q
The point at which the moles of added titrant is stoichiometrically equal to the moles of analyte.
A
Equivalence point
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
12
Q
A ______ is slowly added to another until the reaction between the two is complete.
A
Solution
13
Q
Experiment 5 Title:
A
Determination of Ascorbic Acid in Vitamin C Tablets by Acid-Base Titration.
14
Q
Bronsted-Lowry Acids
A
Proton/H+ Donor
15
Q
Bronsted-Lowry Base
A
Proton/H+ Acceptor
16
Q
It completely dissociates with water
A
Strong Acid/Base
17
Q
It partially dissociates with water.
A
Weak Acid/Base
18
Q
H2SO4, HCl, HBr, HI, HNO3, HClO4
A
Common Strong Acid
19
Q
NaOH, KOH, LiOH
A
Common Strong Base
20
Q
CH3COOH, HF, H3PO4, HSO4-
A
Common Weak Acid
21
Q
NH3, Pyridine, Methylamine
A
Common Weak Base
22
Q
A procedure used in quantitative analysis to determine the concentration of either acid or base.
A
Acid-Base Titration
23
Q
It should change sharply at the equivalence point.
A
Indicator
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
25
It is weak organics acids or bases that dissociates slightly in aqueous solutions to form ions.
Acid Base TIndicator
26
It changes colors because their ions have colors that are different from undissociated molecule.
Indicators
27
A commonly used indicator for acid-base titrations and is a weak acid.
Phenolphthalein
28
The weak acid is ______ and its conjugate base is _____
Colorless
Pink
29
Adding _______ shifts the position of euqilibrium to te left, and turns the indicator _________
H+
Colorless
30
Adding ____ removes the H+ shifts the equilibrium to the right, and turns the indicator ______
Pink
31
Titrant:
Standardized NaOH Solution
32
Analyte
Ascorbic Acid, HC6H7O6
33
Indicator
Phenolphhalein
(Colorless in acidic and neutral solutions pink in basic solution)
34
Endpoint
Faint Pink
35
3 acid-base reactions involved:
1. Standardization of Dilute NaOH
2. Standardization of Dilute of HCl
3. Titration of Ascorbic Acid in Vitamin C Tablet with NaoH
36
HC8H4O4K (aq) + NaOH(aq) → KNaC8H4O4
(aq) + H2O(l)
1. Standardization of Dilute NaOH
37
NaOH (aq) + HCl (aq) → NaCl(aq) + H2O(l)
2. Standardization of Dilute HCl
38
HC6H7O6 (aq) + NaOH (aq) → NaC6H7O6
(aq) + H2O(l)
3. Titration of Ascorbic Acid in Vitamin C Tablet with NaOH
39
An important water-soluble biological antioxidant and free radical scavenger.
Ascorbic Acid
Vitamin C
40
It is required for the growth and repair of the tissues in all parts of the body.
Vitamin c
41
An important protein used to make skin, scar tissue, tendons, ligaments, and blood vessels.
Collagen
42
It is sensitive to heat and light and usually available in 500mg
Vitamin C
43
Alternative technique to direct titration and designed to resolve some roblems encounted in direct titration like slow titration.
Back-Titration
44
A known quantity of ____ is added, greater than the amount required to completely neutralize the ______.
NaOH
ascorbic acid
45
_____ and _______ react completely
NaOH
Ascorbic Acid
46
The excess _______ is titrated with ________ back to the endpoint.
Excess NaOH
Standard HCI Acid
47
The amount consumed in the reaction of back titration is obtained:
molesNaOH reacted = molestotal excess NaOH – molesHCl
48
The _____ that reacted is related to the ________ (ascorbic acid).
amount of NaOH
amount of the analyte
49
Vol NaOH used 🡺 should be total volume not only excess ________
5 mL
50
For direct titration:
mass = MNaOH x VNaOH x molar mass ascorbic acid
51
For back titration:
mass = [(Mexcess NaOH x Vexcess NaOH) – (MHCl x VHCl)] x molar mass ascorbic acid
52
A mild reducing agent and can be determined with the help of a moderate oxidizing agent like iodine in a direct titration with it.
Vitamin C
53
It involves species which undergo reduction-oxidation reaction.
Redox Titrations
54
Two common titration methods (involving I2) based on redox reaction:
Iodimetry and Iodometry
55
Free iodine (I2) is used to titrate a reducing agent; used to quantify a reducing agent.
Iodimetry
56
Iodide (I-) is added that reacts to form iodine (I2), which is then titrated; used to quantify an oxidizing agent.
Iodometry
57
The two reactions involved in this experiment:
1. Generation of I2
2. Oxidation of Vitamin C
58
IO3 − + 6H+ + 5I − → 3I2 + 3H2O
Generation of I2
59
C6H8O6 + I2 → C6H6O6 + 2I− + 2H+
Oxidation of Vitamic C
60
KIO3 solution more stable than I2 as a ___________
Primary standard
61
I2 + 2e - 2I-
Reduction of I2
62
Ascorbic Acid <=> Dehydroascorbic Acid
Oxidation of Erythorbic acid (C6H8O6)
63
A type of direct titration, the reducing agent has to be an analyte.
Iodimetry
64
A technique that involves titrating free iodine with a reducing agent.
Iodimetry
65
A technique that involves titrating free iodine with a reducing agent. As a result, iodine decreases to iodide and oxidizes other species.
Iodimetry
66
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.
Iodometry
67
Iodometry Titrant:
Standard Thiosulfate Solution
68
Iodometry Indicator:
Starch
69
Iodometry Endpoint:
Disapperance of Dark-blue color; from intense blue-black to colorless
70
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.
Potassium Iodate
Potassium Iodide
71
a titration in which the reducing agent is utilized to titrate the iodine formed in the preceding redox reaction
Iodometry
72
a titration in which the reducing agent is used to titrate the iodine solution directly.
iodimetry
73
a method of indirect analysis
Iodometry
74
iodimetry only requires one.
iodimetry
75
involves two redox reactions
Iodometry
76
a form of direct analysis.
iodimetry
77
only requires one.
iodimetry
78
the iodine is oxidized first and subsequently reduced by the reducing agent
Iodometry
79
used in many experiments
Iodometry
80
the iodine is instantaneously reduced.
iodimetry
81
titrations are used less frequently.
iodimetric
82
Quantifying oxidizing compounds is done
iodometry
83
Quantifying reducing agents is done
Iodimetry
84
Titrant:
Analyte: Ascorbic Acid
Indicator: Starch
Endpoint:
Titrant: KIO3 Solution
Endpoint: Blue-Black
85
Title of Experiment 6
Determinaton of Ascorbic Acid by Iodimetry
86
Title of Experiment 7
Determination of Chloride and Sulfate by Precipitation Titration
87
A type of titration that involves the formation of precipitate
Precipitation Titration
88
It is based in the production of precipitation at the end point of the titrimetric analysis.
Precipitation Titration
89
The titrant and analyte combine to create a precipitate, an insoluble material. it continue until all of the analytes have been consumed.
Precipitation Titration
90
Precipitation Titration
Examples of such titrations are often limited to those involving the precipitation of silver ions with anions like ________ or __________
Halogens or Thiocyanate (SCN-)
91
The lack of appropriate ____ is one reason for the limited application of such reactions.
Indicator
92
Sometimes the response rate is too low, especially when titrating dilute solutions.
Precipitation Titration
93
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.
equivalency point
94
▪ 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.
Determination of Unknown Cl-
95
Determination of Unknown Cl-
In this titration, silver chloride precipitates out as a____________-.
White Substance
96
Determination of Unknown Cl-
AgNO3 + Cl– →
AgCl↓ + NO3–
97
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.
AgNO3
potassium chromate (K2CrO4)
98
it has a much lower Ksp value in theory it should precipitate first
* silver chromate
99
uses a small quantity of K2Cr2O4 such that the chloride concentration is much higher than that of chromate. This causes AgCl to preferentially precipitate.
Mohr’s method
100
When all chloride ions in a given sample has all been converted to AgCl, additional AgNO3 reacts with yellow K2CrO4(indicator) to produce ______________.
reddish brown precipitate Ag2CrO4
101
Endpoint is reached when the reddish brown colour remains ‘______’ – does not disappear with stirring.
stable
102
Cl– ions are more reactive than CrO42- so the Ag+ ions preferentially react with Cl– ions first to form a__________before reacting with CrO42–.
white precipitate
103
