6.3 Quantitative Analysis: Titration

Question 1

what is titration

Answer 1

volumetric/quantitative technique to find [unknown] using [known “standard”] in acid-base neutralisation reaction

Question 2

what is a standard solution

Answer 2

solution with a precisely known concentration

Question 3

what’s a volumetric flask

Answer 3

measuring flask

Question 4

what is the analyte

Answer 4

solution in conical flask

Question 5

what is the aliquot

Answer 5

VOLUME of solution in pipette (into conical flask later)

Question 6

what is a burette

Answer 6

long glass tube to deliver solutions

Question 7

how many d.p. can you read off glassware

Answer 7

2 dp

Question 8

ideal indicators for the titrand

Answer 8

phenolphthalein (basic)
methyl orange (acidic)

Question 9

what is the titrant

Answer 9

solution added from burette

Question 10

what is the titrand

Answer 10

leftover titrant

Question 11

what is the titre

Answer 11

VOLUME of solution added from burette

Question 12

5 steps: how to prepare standard solution from solids

Answer 12

(1) distilled water on beaker and rod
(2) weigh solid with beaker
(3) dissolve in water using stirring rod
(4) transfer to solution using volumetric flask
(5) add water and shake

Question 13

rinse all equipment with distilled water to…

Answer 13

get rid of contaminants

Question 14

pipette and burette are finally rinsed with…

Answer 14

liquid they will contain (base in pipette, acid in burette)

Question 15

assume …sig figs for pipette and flask

Answer 15

3

Question 16

how to see colour change in conical flask easier

Answer 16

use white paper underneath

Question 17

what is a primary standard

Answer 17

solution MADE by dissolving accurate solute in solvent

Question 18

what is secondary standard

Answer 18

solution whose concentration is determined by titration against a primary standard

Question 19

hygroscopic solutions…

Answer 19

absorb water
e.g. NaOH, KOH, H2SO4

Question 20

deliquescent solutions…

Answer 20

so hygroscopic that they dissolve
e.g. NaOH, CaCl2, MgCl2

Question 21

[X] solutions are not suitable as primary standards because…

Answer 21

deliquescent solutions, because they absorb water and are impure, unstable

Question 22

efflorescent solutions…

Answer 22

lose water, unstable
e.g. HNaCO3

Question 23

(can/can’t be used?)
(1) anhydrous substance
(2) hydrated substance

Answer 23

(1) yes
(2) no (unstable)

Question 24

5 requirements for primary standard

Answer 24

pure, accurately known concentration, stable, high molar mass, reasonably soluble

Question 25

hydroscopic meaning

Answer 25

absorbs moisture from surroundings = bad as primary standard, unstable

Question 26

if you dilute a solution by 10x, you must…

Answer 26

multiply the final concentration by 10x

Question 27

equivalence point vs end point

Answer 27

equivalence = (theoretical) exact stoichiometric ratio for neutralisation to occur end point = (in practice) when the indicator permanently changes colour

Question 28

axes of a titration curve

Answer 28

pH against mL of added solution (volume)

Question 29

where is the equivalence point on a titration curve

Answer 29

midpoint of period of rapid change in pH

Question 30

indicator used for pH=7

Answer 30

bromothymol blue

Question 31

indicator used for strong base

Answer 31

phenolphthalein (pH>7)

Question 32

indicator used for strong acid

Answer 32

methyl orange (pH<7)

Question 33

(only one/both) solutions must be standard solutions

Answer 33

only one

Question 34

weak acid or weak base on a titration curve has… (2)

Answer 34

(1) a dip at the start (2) shorter vertical section

Question 35

on a titration curve, you can deduce the acid/base pHs by looking at…

Answer 35

the max and min points

Question 36

equivalence points on a conductivity curve are at…

Answer 36

any apex

Question 37

how conductivity curves work

Answer 37

there is a measured difference in ionic charges as ions are being replaced in a solution

Question 38

when do we need back titrations

Answer 38

(1) when it involves solids (2) or volatile substances (accuracy due to loss of substance)

Question 39

what are buffers

Answer 39

weak acid and conjugate base OR weak base and conjugate acid

Question 40

what buffers do

Answer 40

clean up (neutralise) after added H3O+ or OH- until reaction is neutralised

Question 41

what's a buffer region

Answer 41

left region on a titration curve where the pH of a solution remains constant due to the production of a buffer solution

Question 42

7 strong acids

Question 43

7 strong bases

Question 44

sea water buffer system

Question 45

blood buffer system

Question 46

Mohr's method of back titration