Gas tests

Question 1

Zinc (Zn2+) when NaOH or NH3 added

Answer 1

white ppt., soluble in excess, giving a colourless solution

Question 2

Iron(III) (Fe3+) when NaOH or NH3 added

Answer 2

red-brown ppt., insoluble in excess

Question 3

Iron(II) (Fe2+) when NaOH or NH3 added

Answer 3

green ppt., insoluble in excess

Question 4

Copper(Cu2+) when NaOH added

Answer 4

light blue ppt., insoluble in excess

Question 5

Copper(Cu2+) when NH3 added

Answer 5

light blue ppt., soluble in excess, giving a dark blue solution

Question 6

Ammonium (NH4+) when NaOH added

Answer 6

Ammonia produced on warming

Question 7

Calcium(Ca+) when NaOH added

Answer 7

white ppt., insoluble in excess

Question 8

Calcium(Ca+) when NH3 added

Answer 8

no ppt. or very slight white ppt.

Question 9

Carbonate(CO2) test and result

Answer 9

add dilute acid, effervescence| carbon dioxide produced

Question 10

chloride (Cl) [in solution] test and result

Answer 10

acidify with dilute nitric acid, then add aqueous silver nitrate|white ppt.

Question 11

bromide (Br) [in solution] test and result

Answer 11

acidify with dilute nitric acid, then add aqueous silver nitrate|cream ppt.

Question 12

nitrate (NO3) [in solution] test and result

Answer 12

add aqueous sodium hydroxide, then aluminium foil; warm carefully|ammonia produced

Question 13

sulfate (SO,2) [in solution] test and result

Answer 13

acidify, then add aqueous barium nitrate |white ppt.