post lab discussion: exp. 5 Flashcards
briefly explain the type of reaction in titration
acid-base titration (acid-base reaction)
redox titration (electron transfer)
precipitation titration (formation of precipitate)
a technique where a solution of known concentration (titrant) is used to determine the unknown concentration of an identified analyte
titration
Titrant –
Analyte –
Titrant – the solution of known concentration (volume obtained by titration)
Analyte – the solution of unknown concentration (but known volume)
the point at which the moles of added titrant is stoichiometrically equal to the moles of analyte
equivalence point
signals the end of titration where in the indicator gives an observable change like sharp color change; located very close to the equivalence point
endpoint
Bronsted-Lowry Acids -
Bronsted-Lowry Base -
- Bronsted-Lowry Acids - proton/H+ donor
- Bronsted-Lowry Base - proton/H+ acceptor
Strong Acid/Base -
Weak Acid/Base -
Strong Acid/Base - completely dissociates with water
Weak Acid/Base - partially dissociates with water.
*dissociates = break apart/ releasing of ions
examples of strong acid and bases
strong acid: HCI, H2SO4, HBR, HNO3, HI, HCIO4
strong base: NaOH, KOH, LiOH
examples of strong acid and bases
weak acid: CH3COOF, HF, H#PO4, HSO4
weak base: NH3, pyridine, methylamine
is a procedure used in Quantitative Analysis to determine the concentration of either acid or baseis a procedure used in Quantitative Analysis to determine the concentration of either acid or base
acid-base titration
HCl + NaOH —–>
NaCl + H2O
in acid-base titration, the indicator should change sharply at _______
equivalence point
in acid-base titration, the end point of all acids/ bases are neutralised with acid/base, the flask contains ____ and ____ only
sodium chloride (salt)
water
are weak organic acids or bases that dissociates slightly in aqueous solutions to form ions
acid-base indicator
why does indicator changes color
as their ions have colors that are diff from undissociated molecule
what is the color of the acid base indicator of
phenolphthalein-
thymolphthalein-
acid to base
phenolphthalein- colorless to red
thymolphthalein- colorless to blue
is a commonly used indicator for acid-base titrations and is a weak acid
phenolphthalein
is phenolphthalein a weak or strong acid
weak acid
what color is the phenolphthalein when it is weak acid and when it is in conjugate base
weak acid - colorless
conjugate base - pink
from pink to colorless (H+ shifts position of equilibrium to the acid)
from colorless to pink (H+ shifts position of equilibrium to colorless)
in acid base titration, what is the
titrant:
analyte:
indicator:
endpoint:
titrant: standardized NaOH soln.
analyte: ascorbic acid
indicator: phenolphthalein
endpoint: faint pink
chemical formula of ascorbic acid
HC6H7O6
what are the 3 acid-base reactions
standardization of dilute NaOH
standardization of dilute HCI
titration of ascorbic acid
all the products of these eqns has water as their by-product
an important water-soluble biological antioxidant and free radical scavenger
ascorbic acid aka vitamin C
true or false:
humans cannot synthesize ascorbic acid
true
true or false:
sensitive to heat and light
true
is 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
alternative technique to direct titration
back titration
back titration is designed to resolve some problems encountered in ____
direct titration
the amount consumed in the reaction of back titration is obtained:
moles NaOH reacted = moles total excess NaOH - moles HCI
