Lab session 7

Reactions with Alkali

Today, a continuation from last week, we did experiments to investigate the properties of alkali.

Properties of Bases

ACTIVITY #1

1. Place a piece of blue litmus paper, red litmus paper and a drop of universal indicator on a white tile.

2. Carefully add a drop of dilute sodium hydroxide to all three indicators.
3. Repeat steps 1 & 2 with dilute potassium hydroxide and ammonia water.

Results:

Observations:
-Bases turn Red litmus paper blue and blue litmus paper blue.
-Bases have a pH of near 7 to 14.0

ACTIVITY#2

1. Carefully add dilute sodium hydroxide into a test tube up to 2cm in height.
2. Light the Bunsen burner.
3. Carefully add 1 spatula of ammonium chloride to the test tube.
4. Warm the test tube gently over a Bunsen flame:

5. Moisten a piece of red litmus paper and place it at the mouth of the test tube.
6. Gently fan some gas towards your nose.

Results:

Observations:
-Effervescence observed, colorless and pungent gas evolved.
-The gas evolved turned the red litmus paper blue

ACTIVITY #3

1. Using a clean boiling tube, add dilute hydrochloric acid up to 2cm in height.
2. Add 3 drops of universal indicator to the boiling tube:

3. Using a dropper, add 1cm of dilute sodium hydroxide to the acidic the boiling tube and gently shake the boiling tube:

(Starts turning blue-ish. It turned violet but it changed color too fast):

(To yellow)

This is a neutralization process.