inorganic tests

Question 1

test for sulfates (SO4 2-)

Answer 1

● acidify with dilute HCl

● add BaCl2

● white ppt of BaSO4

Question 2

test for carbonate ions (CO3 2-)

Answer 2

● add dilute HCl

● effervescence

● CO2 produced and turns limewater cloudy

Question 3

halide ion (aqueous)

Answer 3

● Cl- :
- acidify with dilute HNO3
- white ppt
- dissolve in dilute NH3

● Br- :
- add AgNO3
- cream ppt
- dissolves in conc NH3

● I- :
- add dilute NH3 followed by conc NH3
- yellow ppt
- insoluble in conc NH3

Question 4

halide ion (solid)

Answer 4

● Cl-
- concentrated sulphuric acid
- effervescence
- damp blue litmus paper turns red

● Br-
- concentrated sulphuric acid
- effervescence
- brown gas produced
- solution turns deep brown / red
- potassium dichromate paper turns

● I-
- brown gas produced
- solution goes brown / red immediately
- lead nitrate paper turns black / grey

Question 5

Mg2+

Answer 5

● add dilute NaOH

● white ppt

Question 6

Ca2+

Answer 6

● add dilute NaOH

● white ppt

● can be differentiated using flame test - red flame

Question 7

Al3+

Answer 7

● add dilute NaOH

● white ppt

● can be differentiated by adding excess NaOH - ppt will dissolve

Question 8

NH4+

Answer 8

● add NaOH and heat sample

● hold damp red litmus paper at test tube mouth

● turns from red to blue

Question 9

group 2 flame tests

Answer 9

● calcium - brick red

● strontium - red

● barium - pale green