Qualitative Analysis 1: Cation test

Experiment 1:

When a few drops of NaOH (aq) was added to a colourless solution, no ppt was observed. Identify the cation present in the colourless solution?

• NH₄⁺

• Ca²⁺

• Cu²⁺

• Fe²⁺

Experiment 1 (Continued):

When warmed, the gas evolved turns moist red litmus paper blue. What is the identity of the gas?

Experiment 2:

When a few drops of NaOH (aq) was added to a light blue solution, a blue ppt was observed. Identify the cation present in the light blue solution?

• NH₄⁺

• Ca²⁺

• Cu²⁺

• Fe²⁺

Experiment 3:

When a few drops of NaOH (aq) was added to a green solution, a green ppt was observed. Identify the cation present in the green solution?

• Zn²⁺

• Ca²⁺

• Fe²⁺

• Fe³⁺

Experiment 3 (Continued):

After some time, what could be observed to the green ppt?

• Green ppt remained green.

• Green ppt turned white.

• Green ppt turned blue.

• Green ppt turned reddish brown.

Experiment 4:

A few drops of NaOH (aq) was added to the colourless solution. A white ppt was observed. What cations could be present in the original colourless solution?

• Zn²⁺

• NH₄⁺

• Al³⁺

• Cu²⁺

• Ca²⁺

Experiment 4 (Continued):

NaOH (aq) was added in excess to the suspension of white ppt. The white ppt dissolved. What cations could be present in the original colourless solution?

• Zn²⁺

• Ca²⁺

• Al³⁺

• Fe³⁺

Experiment 4 (continued):

When an excess of NH₃ (aq) was added to another sample of the colourless solution, a white ppt was observed to dissolve. What cations could be present in the colourless solution?

• Zn²⁺

• Ca²⁺

• Al³⁺

• Fe³⁺