Experiment 1: Preparation and Standardization of 1 N Sulfuric Acid Flashcards
(25 cards)
Reagents
Sulfuric acid
Anhydrous sodium carbonate
Principle
titrimetric/volumetric analysis
USP-NF acceptable range
99 - 100.5%
What is the principle behind the change of color of the solution after adding excess volume of the sulfuric acid (H2S04) solution?
The color change after adding excess sulfuric acid happens because the solution becomes strongly acidic, altering the pH level and causing the indicator to shift to its acid-range color.
This is a visual signal that the titration has passed the end point.
what is the indictor used in the standardization of sulfuric acid?
methyl red
red - 4.4
yellow - 6.2
red in acidic to yellow in basic
endpoint of titration and its pH
pink color
lower range of pH: 4.4–5.0
what is the primary standard used?
anhydrous sodium carbonate
Na₂CO₃
characteristics of the primary standard
- pure
- stable; does not readily absorb moisture or carbon dioxide
- high molar mass
- reacts completely and predictably with acids
what is the analyte?
Sulfuric Acid (H₂SO₄)
what is the secondary standard?
Sulfuric Acid (H₂SO₄)
- The standard for titration
- reacts with H₂SO₄ in a known stoichiometric ratio
Anhydrous Sodium Carbonate (Na₂CO₃)
Sulfuric Acid (H₂SO₄) is a ________ acid used as the analyte whose exact concentration is being determined.
- hygroscopic, corrosive
diprotic acid
- Endpoint detection in acid-base titration (weak acid)
- colorless in acid, pink in base
Phenolphthalein
Standard solution
Sodium carbonate (Na2CO3) solution of known normality (1 N)
Solution to be standardized
Sulfuric acid (approximately 1 N), prepared by dilution
primary standard, secondary standard, or indicator
Anhydrous sodium carbonate
Primary standard
primary standard, secondary standard, or indicator
Concentrated sulfuric acid
Secondary standard
primary standard, secondary standard, or indicator
Phenolphthalein
indicator
primary standard, secondary standard, or indicator
Standard sodium hydroxide solution
Secondary standard
primary standard, secondary standard, or indicator
Potassium biphthalate
Primary standard
Why should sulfuric acid be added slowly to water, not vice versa?
→ Because the reaction is highly exothermic. Adding water to acid can cause the mixture to splash or boil violently, risking burns and accidents.
- Adding acid to water allows better heat control.
solutions of sodium hydroxide or potassium hdyroxide may be standardized by use of a standard solution of ________ or ________ acid as ____________ standard or ____________ as ___________ standard
- hydrochloric or sulfuric acid as secondary standard
- potassium biphthalate as a primary standard
standardization of sulfuric acid solution can also be effected by titration against normal __________ solution using phenolphthalein as an indicator
sodium hydroxide
may be standardized _________ by precipitation and weighing an equivalent amount of ___________, as described under the gravimetric determination of sulfate in a soluble sulfate
- gravimetrically by precipitation
- barium sulfate
