Acid Base Characteristics of Oxides Across the periodic Table

* Pipettes (2)

* Tweezers

* Spatula (2)

* Universal Indicator Paper

* Hydrochloric Acid (2M)

* Sodium Hydroxide (2M)

* Sodium Oxide

* Magnesium Oxide

* Aluminium Oxide

* Silicon Dioxide

* Test Tubes (12)

* Distilled Water

Method:

1. After collecting the required apparatus place the same suitable amount of Sodium Oxide (Na2O) in three different test tubes.

2. In the first test tube add an appropriate amount of distilled water and observe if a reaction occurs. Record these observations. In the solution produced add a small strip of Universal Indicator Paper and record the pH level.

3. In the second test tube add an appropriate amount of Hydrochloric Acid. Observe and record the reaction.

4. In the third test tube add Sodium Hydroxide in an appropriate amount. Observe and record the reaction.

5. Repeat these steps for Magnesium Oxide (MgO), Aluminium Oxide (Al2O3) and Silicon Oxide (SiO2).

NOTE: Phosphorus Pentoxide and Sulfur Dioxide were performed by the teacher.

Data Collection:

Table 1: Appearance Of Oxides

Oxide Name

Appearance

Sodium Oxide

White (creamy), crystallised, clumped

Magnesium Oxide

Powdered, white, very fine, fluffy, slightly grainy

Aluminium Oxide

Extremely fine powder, white, silky

Silicon Dioxide

Beige brown colour with darker and lighter specks, grainy

Phosphorus Pentoxide

White fine powder

Sulfur Dioxide

Clear colourless gas

Table 2: Reaction Of Oxides With Water

Oxide Name

Reaction

pH

Acid/Base

Observations

Sodium Oxide

Yes

11

Base

No real change

Magnesium Oxide

Yes

8

Base

Went cloudy white, magnesium that was not dissolved went to the top, then fell down to the bottom

Aluminium Oxide

No

6

Neutral

Fizzled a little at the start, went cloudy then sediment quickly fell to the bottom

Silicon Dioxide

No

7

Neutral

Didn’t do anything

Phosphorus Pentoxide

Yes

1

Acid

Dissolves instantaneously, gives off heat, loud pop, cloudy

Sulfur Dioxide

Yes

2

Acid

Gas in the air

Table 3: Reaction Of Oxides With An Acid (Hydrochloric Acid 2M)

Oxide Name

Reaction

Observation

Sodium Oxide

Yes

Foam quite vigorous, fizzled high in tube, dropped and fizzles until all oxide was dissolved

Magnesium Oxide

Yes

Completely dissolved very quickly, gave a thin layer of smoke over the top of the liquid and left small bubbles in liquid

Aluminium Oxide

No

No reaction, cloudy then formed a sediment

Silicon Dioxide

Yes

Fizzled to the top of the test tube, kept on doing this for a small period of time then bubbles in liquid

Phosphorus Pentoxide

Fizzles at the start, hard to tell if the water in the acid reacting of the acid. Gives off a little bit of heat

Sulfur Dioxide

N/A

N/A

Table 4: Reaction Of Oxides With A Base (Sodium Hydroxide 2M)

Oxide Name

Reaction

Observation

Sodium Oxide

No

No reaction

Magnesium Oxide

No

No reaction

Aluminium Oxide

No

No reaction

Silicon Dioxide

No

No reaction

Phosphorus Pentoxide

Fizzled a little more than acid, quite warm again could be water in solution

Sulfur Dioxide

N/A

N/A

Conclusion:

The results obtained were inconclusive but suggested that the trend across a period is that it gets more acidic and less basic. Going across a period result in elements loosing their metallic properties. This results in the oxides of metals tending to be basic, whilst the oxides of non-metals have a tendency to be acidic.

Table 2 (Reaction Of Oxides With Water) shows the above conclusion to be true. The results in the literature1 show that the nature of the oxides of period 3 elements go from basic to amphoteric to acidic. This agrees with the results obtained in the tests done with distilled water. The other tests of Hydrochloric Acid and Sodium Hydroxide however do not show any sort of trend in the data obtained.

Improvements to the procedure:

* Testing the same ideas on a different period to see if the theories produced are true for all elements.

* Also try testing electricity conductivity of each of these oxides and seeing if there is any relationship between the two.

* Also to determine trends across a period doing these tests with chlorides of the elements.

* Using different types of acids and bases to see which ones give off the proper reaction that suits the literature and clearly shows whether an oxide is acidic or basic.

1 Chemistry for the IB Diploma – Standard and Higher Level, pg 13-14