post lab discussion: exp. 5

Question 1

briefly explain the type of reaction in titration

Answer 1

acid-base titration (acid-base reaction)
redox titration (electron transfer)
precipitation titration (formation of precipitate)

Question 2

a technique where a solution of known concentration (titrant) is used to determine the unknown concentration of an identified analyte

Answer 2

titration

Question 3

Titrant –
Analyte –

Answer 3

Titrant – the solution of known concentration (volume obtained by titration)
Analyte – the solution of unknown concentration (but known volume)

Question 4

the point at which the moles of added titrant is stoichiometrically equal to the moles of analyte

Answer 4

equivalence point

Question 5

signals the end of titration where in the indicator gives an observable change like sharp color change; located very close to the equivalence point

Answer 5

endpoint

Question 6

Bronsted-Lowry Acids -
Bronsted-Lowry Base -

Answer 6

• Bronsted-Lowry Acids - proton/H+ donor
• Bronsted-Lowry Base - proton/H+ acceptor

Question 7

Strong Acid/Base -
Weak Acid/Base -

Answer 7

Strong Acid/Base - completely dissociates with water
Weak Acid/Base - partially dissociates with water.

*dissociates = break apart/ releasing of ions

Question 8

examples of strong acid and bases

Answer 8

strong acid: HCI, H2SO4, HBR, HNO3, HI, HCIO4
strong base: NaOH, KOH, LiOH

Question 9

examples of strong acid and bases

Answer 9

weak acid: CH3COOF, HF, H#PO4, HSO4
weak base: NH3, pyridine, methylamine

Question 10

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

Answer 10

acid-base titration

Question 11

HCl + NaOH —–>

Answer 11

NaCl + H2O

Question 12

in acid-base titration, the indicator should change sharply at _______

Answer 12

equivalence point

Question 13

in acid-base titration, the end point of all acids/ bases are neutralised with acid/base, the flask contains ____ and ____ only

Answer 13

sodium chloride (salt)
water

Question 14

are weak organic acids or bases that dissociates slightly in aqueous solutions to form ions

Answer 14

acid-base indicator

Question 15

why does indicator changes color

Answer 15

as their ions have colors that are diff from undissociated molecule

Question 16

what is the color of the acid base indicator of
phenolphthalein-
thymolphthalein-

Answer 16

acid to base
phenolphthalein- colorless to red
thymolphthalein- colorless to blue

Question 17

is a commonly used indicator for acid-base titrations and is a weak acid

Answer 17

phenolphthalein

Question 18

is phenolphthalein a weak or strong acid

Answer 18

weak acid

Question 19

what color is the phenolphthalein when it is weak acid and when it is in conjugate base

Answer 19

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)

Question 20

in acid base titration, what is the
titrant:
analyte:
indicator:
endpoint:

Answer 20

titrant: standardized NaOH soln.
analyte: ascorbic acid
indicator: phenolphthalein
endpoint: faint pink

Question 21

chemical formula of ascorbic acid

Answer 21

HC6H7O6

Question 22

what are the 3 acid-base reactions

Answer 22

standardization of dilute NaOH
standardization of dilute HCI
titration of ascorbic acid

all the products of these eqns has water as their by-product

Question 23

an important water-soluble biological antioxidant and free radical scavenger

Answer 23

ascorbic acid aka vitamin C

Question 24

true or false:
humans cannot synthesize ascorbic acid

Answer 24

true

Question 25

true or false:
sensitive to heat and light

Answer 25

true

Question 26

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.

Answer 26

vitamin C

Question 27

alternative technique to direct titration

Answer 27

back titration

Question 28

back titration is designed to resolve some problems encountered in ____

Answer 28

direct titration

Question 29

the amount consumed in the reaction of back titration is obtained:

Answer 29

moles NaOH reacted = moles total excess NaOH - moles HCI