PRELIMINARY TESTS

Question 1

Describe the procedure for dry heating with precautions

Answer 1

In a dry test tube , the sample is taken and heated over a flame in a tilted position while keeping the tube pointing away from any individual in the lab .

Question 2

What is observed for ZnO / Zn salts , PbO/Pb salts, and CdO/ Cd salts during dry heating respectively ?

Answer 2

ZnO / Zn salts- yellow (hot) , white (cold)
PbO/Pb salts- yellow (hot and cold)
CdO/ Cd salts-brown (hot and cold)

Question 3

What is observed during dry heating of Cu, Ni , and Mn salts ?

Answer 3

there is blackening of salts without odor

Question 4

Describe the gases that evolved for various anions during dry heating

Answer 4

DARK BROWN FUMES - NO3-,Br-,I-, NO2-
AMMONIA SMELL - ammonium salts
ROTTEN EGG SMELL - S2-

Question 5

Describe the sublimates formed on dry heating

Answer 5

WHITE - NH4Cl / NH4+ salts
YELLOW- S2-
BLUE TO BLACK - I-

Question 6

What cations on flame test give golden yellow, bluish-green , apple green respectively ?

Answer 6

Na+,Cu+, and Ba2+

Question 7

Describe the procedure for the flame test. And why is a reagent used?

Answer 7

A platinum wire is dipped in conc. HCl and tapped lightly in the slat and exposed to the hottest part of the flame . Conc. HCl is used to get rid of additional impurities that can hinder the result .

Question 8

What cations give brick red, deep red, and bluish-white respectively ?

Answer 8

Ca2+ (Sr(NO3)2), Sr2+ and Pb2+

Question 9

what does the cation K+ give on the flame test?

Answer 9

bluish - violet

Question 10

Mention the procedure and observations for the iodine azide test and the cation/anion it identifies .

Answer 10

The sample is exposed to iodine azide which if S2- is present causes the color to discharge with slow effervescence.

Question 11

Which anion gives light brown fumes with dil H2SO4?

Answer 11

NO2-

Question 12

What is observed when a carbonate salt is exposed to dil. H2SO4?

Answer 12

Brisk effervescence and lime water turn milky.

Question 13

what are the observations when acetate ion and sulfide anions are present in the salt respectively ?

Answer 13

vinegar smell and rotten egg smell

Question 14

Mention the observations made when the halide ions are exposed to conc. H2SO4

Answer 14

Cl- ( pungent-smelling gas which gives dense white fumes of NH4Cl with NH4OH)
Br- (pungent smell and light brown fumes which deepen with Mn02)
I - ( Violet vapours which turn starch paper blue)