5.3.2 - Qualitative analysis

Question 1

Plan a procedure on a test tube scale to show that the solid mixture contains thefollowing ions:
-NH4+
- Fe2+
- SO4 2−
present in (NH4)2Fe(SO4)2*xH2O
- CO3 2− present in crushed limestone.
Show your reasoning, including relevant equations. (6)

Answer 1

Practical details:
- Sample stirred with water and mixture filtered
- SO4 2−, Fe2+, NH4+ tests on filtrate.
- CO3 2− test on residue or garden
product

Tests and associated equations:

CO3 2− test:

Test: Add nitric acid.
Observation:effervescence.
Equation: CaCO3 + 2H+ → Ca2+ + CO2 +H2O
ALLOW CO3 2− + 2H+ → CO2 + H2O

Fe2+ test:
Test: Add NaOH(aq)
Observation: green precipitate
Equation: Fe2+ + 2OH− → Fe(OH)2

NH4+ test:
Test: Add NaOH(aq) and warm
Observation: gas turns red litmus
indicator blue
Equation: NH4 + + OH− → NH3 + H2O