Qualitative Analysis

Open Ended

Watch this video

Cations (Zn(II), Al(III), Cu(II), Fe(II) and Fe(III): Tested with NaOH. - YouTube

http://www.youtube.com/watch?v=3COr0ol1AxM&feature=fvwrel

1. What is the reagent added to the solutions each containing a cation?

Open Ended

Watch this video

Cations (Zn(II), Al(III), Cu(II), Fe(II) and Fe(III): Tested with NaOH. - YouTube

http://www.youtube.com/watch?v=3COr0ol1AxM&feature=fvwrel

2. What is the colour of each precipitate formed?

Open Ended

Watch this video

Cations (Zn(II), Al(III), Cu(II), Fe(II) and Fe(III): Tested with NaOH. - YouTube

http://www.youtube.com/watch?v=3COr0ol1AxM&feature=fvwrel

3. Is the precipitate soluble in excess reagent?

​How to learn?

As we go along, take note of the cations that give coloured ppts, then those cations which are white ppt and lastly those with no ppt.

​Re-cap

The precipitates formed are metal hydroxides. Some of them dissolve in excess reagent due to the formation of compounds that are soluble in water.

​For Fe(II) test, the green ppt turns reddish brown when left to stand due to oxidation of the Fe²⁺ ions

Open Ended

Why does the white ppt dissolve in excess NaOH(aq) to form a colourless solution for Zn²⁺ and Pb²⁺ ?

Open Ended

Why does Ca²⁺ form a precipitate with NaOH(aq) but not with NH₃(aq)?

Open Ended

Testing anion - chloride ion

https://www.youtube.com/watch?v=TNj0PcSag1k

What do you observe in the test tube?

What is the name of product formed?

Open Ended

Testing anion - sulfate ion

http://www.youtube.com/watch?v=Zm4NeAjmZbY&p=ED5C5C040AE82D23&index=2&playnext=2

What do you observe in the test tube?

Multiple Choice

Excess aqueous sodium hydroxide is added to salt X and the solution is heated. A gas is given off which turns red litmus blue.

When this reaction is complete, aluminium foil is added to the solution. A gas is gain given off which also turns red litmus blue.

What is salt X?

• ammonium nitrate

• ammonium sulfate

• zinc nitrate

• zinc sulfate

Multiple Choice

A white crystalline solid, X, is heated with aqueous sodium hydroxide and aluminium. A piece of red litmus paper, held near the mouth of the test-tube, remains red while the mixture is heated for several minutes.

Which conclusion must be correct?

• An acidic gas was given off.

• X is acidic.

• X is magnesium.

• X is not ammonium chloride.

​In your notebook, please complete:

(1) Test Yourself 11.3

(2) Let's Review Section B Q2-3 i