Aq Cations

Question 1

Reppt using HNO3 for?

Answer 1

Al3+: white ppt reppted; soluble in xs HNO3 to give a colourless sol

Zn2+: white ppt reppted; soluble in xs; colourless sol

Cr3+: grey green ppt reppted; soluble in xs; dark green

Cu2+: pale blue ppt reppted; soluble; pale blue sol
(NH3)

Question 2

How to test for Zn2+?

Answer 2

Rinmann’s green ash test

• 3 4 drops of test sol to a price of filter paper;
• same spot, few drops of cobalt(II) nitrate;
• burn in evaporating dish

Question 3

How to test for NH4+

Answer 3

• 2cm3 depth of sol;
• equal amt of NaOH
• warm;
• ID gas evolved