ACIDS AND BASES (LAB) Flashcards
is a method of quantitative analysis for determining the concentration of an acid or base by exactly neutralizing it with a standard solution of base or acid having known concentration.
Acid-Base Titration
is used to monitor the progress of the acid–base reaction.
pH indicator
solution of known concentration
Titrant
solution of unknown concentration
Analyte
2 types of acid-base titration:
Indicator-based titration
Potentiometric Titration
the indicator changes color at the equivalence point
Indicator-based titration
is colorless in acidic solutions and pink in basic solutions.
Phenolphthalein
red in acidic solutions and yellow in basic solutions
Methyl orange
pH of the solution is monitored using a pH meter
Potentiometric Titration
: is the process by which our bodies convert food into energy
Metabolism
: use to maintain the pH of the blood. It consists of carbonic acid (H2CO3) and bicarbonate ion (HCO3-).
Bicarbonate buffer system
DIFFERENT TYPES OF BUFFERS
Bicarbonate buffer system
Protein buffer system
Nucleic acid buffer system
to measure the acidity or alkalinity of water, which is important for ensuring that water is safe to drink and use.
Water quality testing
: to measure the acidity of food and beverages, which is important for ensuring that they have the correct flavor and shelf life.
Food and beverage analysis
: to detect the presence of tyrosine or tryptophan, which are aromatic amino acids. The test reagent is a solution of mercury(II) nitrate and concentrated nitric acid. When the test reagent is added to a protein that contains tyrosine or tryptophan, a red precipitate is formed.
Millon’s test
to detect the presence of the amino acid, tryptophan. The test reagent is concentrated nitric acid. When the test reagent is added to a protein that contains tryptophan, a yellow precipitate is formed.
Xanthoproteic test
to detect the presence of the amino acid, tyrosine. The test reagent is a solution of concentrated hydrochloric acid and sodium nitroprusside. When the test reagent is added to a protein that contains tyrosine, a purple-red ring forms at the interface of the two solutions.
Hopkins-Cole test
to detect the presence of peptide bonds, which are linkages between amino acids. The test reagent is a solution of copper(II) sulfate and sodium hydroxide. When the test reagent is added to a protein, a purple color forms.
Biuret test
to detect the presence of amino acids. The test reagent is a solution of ninhydrin in concentrated sulfuric acid. When the test reagent is added to a protein, a purple color forms.
Ninhydrin test:
: The test reagent is a solution of a metallic salt, such as lead acetate or mercuric chloride. When the test reagent is added to a protein, a white precipitate may form.
Precipitation by metallic salts:
The test reagent is a solution of an alkaloidal reagent, such as tannic acid or picric acid. When the test reagent is added to a protein, a white precipitate may form.
Precipitation by alkaloidal reagents:
This test is used to detect the presence of the amino acid, cysteine. The test reagent is a solution of ferric chloride. When the test reagent is added to a protein that contains cysteine, a blue color forms.
Heller’s test
This is a process by which proteins are precipitated from solution by the addition of a salt, such as ammonium sulfate. The salt disrupts the interactions between the water molecules and the protein molecules, causing the protein molecules to aggregate and precipitate.
Salting out
This is a process by which proteins are denatured and precipitated by heat or by the addition of an acid or base. The denaturation of proteins disrupts the structure of the protein molecules, causing them to aggregate and precipitate
Coagulation test
