7.8 Qualitative Ionic Analysis

Question 1

what is an “element’s spectrum”

Answer 1

characteristic patten of wavelengths absorbed and emitted (frequencies)

Question 2

the motion of ions in an ionic compound solution

Answer 2

move freely around because ion-dipole attraction to water is stronger than the ion-ion salt attraction

Question 3

precipitation reaction forms when…

Answer 3

mixed ions create ion-ion attraction that’s stronger than water’s ion-dipole attraction

Question 4

STEP 1 cation: what forms white precipitate with chloride

Answer 4

Pb2+ and Ag+

Question 5

STEP 1.5 cation: how to tell Pb2+ and Ag+ apart

Answer 5

(1) AgCl goes violet on standing
(2) add OH- so AgOH is brown and Pb(OH)2 is white
(3) add I- so AgI is lemon yellow and PbI2 is canary yellow

Question 6

STEP 2 cation: what forms white precipitate with sulphate

Answer 6

Ba2+ and Ca2+

Question 7

STEP 2.5 cation: how to tell Ba2+ and Ca2+ apart

Answer 7

flame test. Ba2+ is white, Ca2+ is orange

Question 8

STEP 3 cation: determine precipitate colours of remaining cations after adding OH-

Mg2+
Cu2+
Fe2+
Fe3+

Answer 8

Mg2+ white
Cu2+ blue
Fe2+ green turning brown
Fe3+ brown

Question 9

(cations) how to identify Mg2+ from Ba2+ and Ca2+

Answer 9

reaction with SO4(2-) is aqueous

Question 10

as Ksp gets bigger, the solubility…

Answer 10

increases

Question 11

what are complex ions

Answer 11

small molecules/ions attach themselves to a central cation (usually a transition metal)

Question 12

what are ligands

Answer 12

the surrounding molecules/ions of a central cation.

acts as an electron pair donor

Question 13

what is coordinate covalent bond

Answer 13

the name of bond between metal ion and ligand

Question 14

how are coordinate covalent bonds formed

Answer 14

when empty orbitals of the metal cation accepts a lone pair of electrons from each ligand

Question 15

STEP 1 anion: add acid, and whichever bubbles is…

Answer 15

carbonate

Question 16

STEP 2 anion: add Fe3+(aq) to get phosphate and hydroxide precipitates

Answer 16

PO4(3-) pink
OH- brown

Question 17

STEP 3 anion: add Ba2+(aq) e.g. Ba(NO3)2

Answer 17

thick white precipitate is SO4(2-)

Question 18

STEP 4 anion: add Ag+ to Cl-, Br-, I-, and CH3COO-

Answer 18

Cl- white
Br- cream
I- yellow
CH3COO- no reaction

Question 19

STEP 4.5 anion: if unsure, add dilute NH4OH

Answer 19

if it redissolves, it’s Cl-

Question 20

STEP 4.6 anion: then add concentrated NH4OH

Answer 20

if redissolves, its Br-
if precipitate still then I-