Basic Titrations
Chemicals and Apparatus
Chemicals: standard
solution, indicator,
electrolyte solution
etc.
Apparatus: buret, buret
stand, clamp,
Erlenmeyer flask,
pipet, volumetric flask,
analytical balance etc.
What grades of chemicals are classified?
USA
1. Reagent grade
2. Primary-standard grade
3. Special-purpose reagent chemicals
China
1. Industrial
2. Chemical
3. Analytical
4. Special-purpose reagent chemicals
Analytical Balances
0.1mg
1mg
型号
TG-328A
TG-328B
最大秤量(g)
200
200
分度值(mg)
0.1
0.1
光学读数范围
0.1～10mg
0.1～10mg
机械加码范围
0.01～199.99g
10～990mg
秤盘直径(mm)
Φ75
Φ75
外形尺寸(mm)
440×400×500
440×400×500
净重(kg)
16
15
1.
2.
3.
4.
5.
6.
7.
8.
9.
Rules for handing reagents and solutions (P23)
Rules in using an analytical balances (P28)
Sources of errors in weighing (P29)
What are the function of desiccators?(P32)
How to manipulate weighing bottles?(P33)
Weighing by direct or difference(P34)
Using pipets (P42,P46); buret(P44, P46); volumetric
flasks(P44, P49)
Calibrating volumetric ware (P50): (1) calibrating a
buret; (2) Calibrating a volumetric flask relative to a
pipet
Tips about your laboratory notebook (P52)
What are the three essential attributes of a
laboratory notebook?
(a)
1. Record what you did.
2. Write in complete sentences.
3. The notebook should be understandable by a stranger.
(b)
1. Record what you did.
2. Record what you observed.
3. Always write balanced equations.
(c)
1. Record what you did.
2. Record what you observed.
3. The notebook should be understandable by a stranger.
• Safety is a major issue in the laboratory.
Laboratory workers must wear protective
glasses at all times. Food and chemicals don't
mix. Protect your body with long pants and a lab
coat if possible. Never wear sandals to lab.
Protect your feet from spills with real shoes. If
you happen to have an accident, such as spilling
a chemical on your body, what do think to deal
with the situation?
•
1. Don't panic.
2. Get help immediately.
3. Notify your laboratory instructor.
4. Wash the area with a mild detergent and
water.
5. Remove contaminated clothing if necessary.
6. Get medical attention.
Titrations
Terms
•
•
•
•
•
•
•
Titrimetry, Titration, Back-titration
Standard solution ( Standard titrant)
indicator
Equivalence point (Stoichiometric point)
End point
Titration error
Titration Curves
• What are primary standards and
secondary standards? Please give some
examples.
• What are the desirable properties for
standard solutions?
• How did we prepared the standard
solutions?
• How did we express the concentration of
the standard solutions?
Volumetric Calculations
• Molarity of standard solution
• Treating titration data
(1)calculating molarity from standardization
data
(2) Calculating the quantity of analyte from
titration data
Please study the examples in your textbook!
How did we determine the end point?
1. Changes in color due to the reagent, the
analyte, or an indicator
2. Changes in potential of an electrode that
responds to the concentration of the
reagent or the analyte
Titration Curves
• Titration Curves are plots of a concentrationrelated variable as a function of reagent
volume.
• Types of Titration Curves
– A Sigmoidal curve, in which the p-function of the
analyte is plotted as a function of reagent volume.
– Linear-segment curve measurements are made on
both sides of the equivalence point, but not near the
equivalence point. In this type of curve, the y-axis is
an instrument reading that is directly proportional to
the concentration of the analyte or reagent present.
Concentration changes during titrations
Study the feature 11-2 (P260) to understand the calculation.
1. How to select standard solutions
2. What are indicators? what is indicator range? How to
select indicators? (Theory of Indicator Behavior)
3. Titration Curves (calculate pH during titration)
(1) The titration of a strong acid with a strong base
(2) The titration of a strong base with a strong acid
(3) The titration of a weak acid with a strong base
(4) The titration of a weak base with a strong acid
4. How do the concentrations effect on the shape of the
curve?
5. The effect of reaction completeness
6. The definition and properties (e.g. buffer capacity) of
buffer solution
7. Calculation of pH of the buffer solution