4.5.1 - Laboratory Activity : Determining the properties of oxide of elements in Period 3.

Laboratory Activity 4.5.1: Determining the properties of oxide of elements in Period 3.

Aim: To study the changes of oxide properties for elements in Period 3.
Problem statement: How do the properties of element oxides changes across the Period 3?
Hypothesis: Oxide properties of Period 3 change from base to acid when crossing the period.
Variable:

	»	Fixed variable : Oxygen and water
	»	Manipulated variable : Type of element oxide
	»	Responding variable : Changes in properties

Material: » Sodium oxide » Magnesium oxide » Aluminium oxide » Silicon (IV) oxide » Phosphorus oxide » Sulphur dioxide » Dichlorine heptoxide » Universal indicator » Water

Apparatus: » Bunsen burner » Glass rod » Rubber stopper » Test tube » Test tube holder

Procedure:

	►	(A) With water 1. 10ml of water is added to half spatula of sodium oxide in a test tube and the contents are shaken. 2. 2 drops of universal indicator are added to the mixture and the pH of the solution is noted. 3. Step 1 and 2 are repeated with other oxide. All observations are recorded.
	►	(B) With sodium hydroxide and nitric acid 1. Half spatula of sodium oxide powder is put into two separate test tubes. 2. 10ml of sodium hydroxide 2 is added to one test tube. 3. 10ml of nitric acid 2 is added to another test tube. 4. The contents in each test tube are heated slowly while being stirred with glass rods. 5. The solubility of the oxide in both solutions are observed and recorded. 6. Step 1- 5 are repeated with other oxide.

Results:

►

Observation Oxide With water pH value With NaOH With HNO3 Na2O Soluble. Forms colourless solution. 13 - 14 Insoluble Soluble. Forms colourless solution MgO Slightly soluble. Forms colourless solution. 8 - 9 Insoluble Soluble. Forms colourless solution. Al2O3 Insoluble 7 Soluble. Forms colourless solution. Soluble. Forms colourless solution. SiO2 Insoluble 7 Soluble. Forms colourless solution. Insoluble P4O10 Soluble. Forms colourless solution. 2 - 3 Soluble. Forms colourless solution. Insoluble SO2 Soluble. Forms colourless solution. 2 - 3 - - Cl2O7 Soluble. Forms colourless solution. 1 - -

Discussion:

	►	Inference Oxide Inference Na2O Strong base. Forms a strong alkali. Exhibits metallic nature. React with acids to form salt and water. Na2O(p) + 2HNO3(aq) → 2NaNO3(aq) + H2O(l) MgO A basic oxide. Forms a weak alkali. Exhibits metallic nature. React with acids to form salt and water. MgO(p) + 2HNO3(aq) → Mg(NO3)2(aq) + H2O(l) Al2O3 An amphoteric oxide. Show semi-metallic nature. Reacts with both acids and alkalis to form a salt and water. Al2O3(s) + 6HNO3(aq) → 2Al(NO3)3(aq) + 3H2O(l) Al2O3(s) + 2NaOH(aq) → 2NaAlO2(aq) + 3H2O(l) SiO2 An acidic oxide. Show non-metallic nature. SiO2(s) + 2NaOH(aq) → Na2SiO3(aq) + H2O(l) P4O10 An acidic oxide. Show non-metallic nature. P4O10(s) + 12NaOH(aq) → 4Na3PO4(aq) + 6H2O(l) SO2 Forms an acid. An acidic oxide. Show non-metallic nature. Cl2O7 Strong acid formed. An acidic oxide. Show non-metallic nature.
	►	Solubility in water decreases from Group 1 to 13 for metals.
	►	Solubility in water increases from Group 14 to 17 for non-metals.

Conclusion:

►

The oxides of elements in Period 3 change from basic to amphoteric, and then to an acidic nature when across Period 3 from left to right.

↶ 4.5 Elements in a period

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