Chapter 14: Applications of Neutralization Titrations Flashcards
TRUE or FALSE
Solutions of HCl, HClO4, and H2SO4 are stable indefinitely. Restandardization is not required unless evaporation occurs.
TRUE
widely used as standard solutions for titrating bases
HCl
TRUE or FALSE
solutions of 0.1 M HCl can be boiled for as long as an hour without loss of acid, provided that the water lost by evaporation is periodically replaced
TRUE
TRUE or FALSE
0.5 M solutions can be boiled for at least 10 minutes without significant loss
TRUE
TRUE or FALSE
Standard solutions of nitric acid is seldom used because of its oxidizing properties
TRUE
To obtain most standard acid solutions, a solution of an approximate concentration is first prepared by diluting the concentrated reagent. The diluted acid solution is then standardized against a
primary-standard base
TRUE or FALSE
Primary-standard–grade sodium carbonate is available commercially or can be prepared
by heating purified sodium hydrogen carbonate between 270C and 300C
for 1 hour
TRUE
is the most common base for preparing standard solutions, although potassium hydroxide and barium hydroxide are also used.
sodium hydroxide
The effective concentration of the base is thus diminished by absorption of carbon dioxide, and a systematic error called the
carbonate error
TRUE or FALSE
Carbonate ion in standard base solutions decrease the sharpness of end points and is usually removed before standardization.
TRUE
is a nearly ideal primary standard. It is a nonhygroscopic crystalline solid with a relatively large molar mass (204.2 g/mol)
KHP (potassium hydrogen phthalate)
Several excellent primary standards are available for standardizing bases but most are ___________ that require the use of an indicator with a basic transition range
weak organic acids
what bases are used for standardization of acids
sodium carbonate
TRIS (tris-hydroxymethylaminomethane)
sodium tetraborate decahydrate
mercury (II) oxide
TRUE or FALSE
In solution as well as in the solid state, the hydroxides of sodium, potassium, and barium
react rapidly with atmospheric carbon dioxide to produce the corresponding carbonate
TRUE
TRUE or FALSE
the presence of carbonate ions does not cause a carbonate error provided the same indicator is used for both standardization and analysis, which carbonate does, however, decrease the sharpness of end points and thus is removed before a solution of a base is standardized
TRUE
TRUE or FALSE
best method for preparing carbonate-free sodium hydroxide solutions is to vacuum filter the carbonate given its low solubility
TRUE
TRUE or FALSE
A tightly capped low-density polyethylene bottle usually provides adequate shortterm
protection against the uptake of atmospheric carbon dioxide
TRUE
is an excellent primary standard with a
high molar mass per mole of protons. It is also a strong acid that can be titrated using
virtually any indicator with a transition range between pH 4 and 10.
potassium hydrogen iodate
what acids are used in standardizing bases
potassium hydrogen phthalate
benzoic acids
potassium hydrogen iodate
are used to determine the many inorganic, organic, and biological species that possess acidic or basic properties
neutralization titrations
2 major types of end points
visual end point
potentiometric end point
the potential of a glass/calomel electrode system is determined with a pH meter or another voltage measuring device
potentiometric endpoint
what elements that occur in organic and biological systems are conveniently determined by methods that have an acid-base titration as the final step
nonmetal elements
carbon
nitrogen
chlorine
bromine
fluorine
occurs in a wide variety of substances of interest in the life sciences, in industry, and in agriculture. Examples include amino acids, proteins, synthetic drugs, fertilizers, explosives, soils, potable water supplies, and dyes
nitrogen
most common method for determining organic nitrogen is the. sample is decomposed in hot conc sulfuric acid to convert the bound nitrogen to ammonium ion, which is then cooled, diluted, and made basic
Kjeldahl method
a reagent containing copper(II) ions is used, and a violet colored complex is formed between the Cu21 ions and peptide bonds. The increase in the absorption of visible radiation is used to measure serum protein
Biuret method
the serum sample is pretreated with an alkaline copper solution followed by a phenolic reagent. A color develops because of reduction
of phosphotungstic acid and phosphomolybdic acid to molybdenum blue
lowry method
the sample is mixed with powdered copper(II)
oxide and ignited in a combustion tube to give carbon dioxide, water, nitrogen, and
small amounts of nitrogen oxides
Dumas method
are conveniently determined by conversion to ammonia with strong base followed by distillation. The ammonia is collected and titrated as in the Kjeldahl method.
ammonium salts
50% Cu, 45% Al, and 5% Zn
devarda’s alloy
The method just described for ammonium salts can be extended to the determination
of what inorganic substances
nitrates and nitrites
The _________ of an acid or base is the mass of the compound that reacts with or contains 1 mole of protons
equivalent mass
is the process by which an ester is hydrolyzed in alkaline solution to give an alcohol and a conjugate base.
saponification
also called as the equivalent weight
equivalent mass
generally have base dissociation constants on the order of 10^-5 and can be titrated directly with a solution of strong acid
amine groups
have dissociation constants that range between 1024 and 1026, and thus, these compounds are readily titrated. An indicator that changes color in a basic range, such as
phenolphthalein, is required.
carboxylic and sulfonic acids
are commonly determined by saponification with a measured quantity of standard base
ester groups
can be determined by esterification with
various carboxylic acid anhydrides or chlorides. The two most common reagents are
acetic anhydride and phthalic anhydride.
Hydroxyl groups in organic compounds
can be determined with a solution of hydroxylamine hydrochloride.
carbonyl groups
TRUE or FALSE
The total salt content of a solution can be determined accurately by acid-base titration.
The salt is converted to an equivalent amount of an acid or base by passing a
solution containing the salt through a column packed with an ion-exchange resin
TRUE
is an ion or a molecule that
forms a covalent bond with a cation
or a neutral metal atom by donating
a pair of electrons, which are then
shared by the two.
ligand
A stock solution with a known hydrochloric acid concentration can also be prepared by diluting a quantity of the concentrated reagent with an equal volume of water followed by distillation. Under controlled conditions, the
final quarter of the distillate, known as _________________HCl, has a constant and known composition.
constant-boiling
can be prepared by heating purified sodium hydrogen carbonate between 270 and 300 degrees celsius for 1 hour
primary standard grade sodium carbonate
TRUE or FALSE
The second end point is always used
for standardization because the change in pH is greater than that at the first
TRUE
most common base used in titrtaion
sodium hydroxide
potassium hydroxide
barium hydroxide
with atmospheric constituents
contains only about 1.5 3 1025
mol CO2 /L, an amount that
has a negligible effect on the
strength of most standard bases.
As an alternative to boiling to
remove CO2 from supersaturated
solutions of CO2, the excess gas
can be removed by bubbling air
through the water for several
hours. This process is called
sparging
sparging produced what
a solution that contains the equilibrium concentration of CO2
is the process of removing
a gas from a solution by bubbling an
inert gas through the solution
sparging
can be obtained in primary-standard purity and used for the standardization of bases has limited solubility in water, so it is usually dissolved in ethanol prior to dilution with water and titration
benzoic acid
s an excellent primary standard with a
high molar mass per mole of protons. It is also a strong acid that can be titrated using
virtually any indicator with a transition range between pH 4 and 10.
potassium hydrogen iodate
are particularly resistant to complete decomposition by sulfuric acid
pyridine
pyridine derivatives
some other heterocyclic compounds
is frequently the most time-consuming aspect of a Kjeldahl determination.
decomposition step
_______ in organic and biological materials is conveniently determined by burningthe sample in a stream of oxygen.
sulfur
are conveniently determined by conversion to ammonia with strong base followed by distillation
ammonium salts
These ions are first reduced to ammonium ion by reaction with an alloy of 50% Cu, 45% Al, and 5% Zn (Devarda’s alloy)
nitrates and nitrites
60% Cu and 40% Mg is called
Arnd’s alloy
a method in which both components are titrated with a standard acid to the end point with an acid-range indicator, such as bromocresol green (the end
point being established after the solution is boiled to remove carbon dioxide).
Winkler method
provide convenient methods for the direct or indirect determination of several organic functional groups
neutralization titrations
have dissociation constants that range between 10^4 and 10^6, with low solubility in water but readily soluble in ethanol
caboxylic acids
are generally strong acids that easily dissolve in water
sulfonic acid
generally have base dissociation constants on the order of 10^5 and can be titrated directly with a solution of strong acid.
aliphatic amines
ommonly determined by saponification with a measured quantity of standard base, which is then titrated with standard acid
ester groups
TRUE or FALSE
The total salt content of a solution can be determined accurately by acid-base titration.
The salt is converted to an equivalent amount of an acid or base by passing a
solution containing the salt through a column packed with an ion-exchange resin
TRUE
