3.1.6Additional lessons
Metallic and Non-Metallic Oxides — IB Chemistry HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 53 of 172
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5Acid-Base Character
Metal oxides
- Metal oxides Oxides of metals are usually basic, forming hydroxides in water or neutralising acids to give a salt and water.
Non-metal oxides
- Non-metal oxides Oxides of non-metals are usually acidic, forming oxoacids in water or reacting with alkalis to give salts.
Amphoteric oxide
- Amphoteric oxide Aluminium oxide reacts with both acids and strong alkalis, showing both basic and acidic behaviour.
Neutral oxides
- Neutral oxides Oxides such as CO, NO and N₂O do not react with water to form acids or bases.
Bonding link
- Bonding link Oxides of metals are ionic and contain O²⁻, while oxides of non-metals are covalent molecular or giant structures.
Section 2 of 5Period 3 Oxides
1
Na₂O + H₂O → 2NaOH is a strongly alkaline solution, and MgO is only slightly soluble giving a weak alkaline solution.
2
Al₂O₃ is insoluble in water but dissolves in both acid and alkali, so it is amphoteric.
3
SiO₂ is a giant covalent oxide that is insoluble in water but dissolves slowly in hot concentrated alkali, so it is acidic.
4
P₄O₁₀ + 6H₂O → 4H₃PO₄ gives an acidic solution.
5
SO₂ + H₂O ⇌ H₂SO₃ and SO₃ + H₂O → H₂SO₄ give acidic solutions, with sulfur trioxide the stronger acid.
| Oxide | Type | Example reaction |
|---|---|---|
| Na₂O | Basic | Na₂O + 2HCl → 2NaCl + H₂O |
| Al₂O₃ | Amphoteric | Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O |
| SO₃ | Acidic | SO₃ + 2NaOH → Na₂SO₄ + H₂O |
Section 3 of 5Acid Rain Link
Acid Rain Link
Sulfur dioxide
- Sulfur dioxide Burning fossil fuels containing sulfur releases SO₂, which dissolves in rain to form sulfurous acid.
Nitrogen oxides
- Nitrogen oxides NO and NO₂ form in engines at high temperature, and NO₂ dissolves to give nitric acid in rainwater.
Carbon dioxide
- Carbon dioxide CO₂ dissolves to give a weak acid, H₂CO₃, which lowers the pH of pure rainwater to about 5.6.
Neutralising
- Neutralising Calcium oxide or carbonate is used to neutralise acidic gases from chimneys and acidic soil.
Section 4 of 5Worked Example
Question
- 3.10 g of Na₂O dissolves in water to make 500 cm³ of solution.
- Calculate [NaOH].
- M(Na₂O) = 2 × 22.99 + 16.00 = 61.98 g mol⁻¹, so n = 3.10 ÷ 61.98 = 0.0500 mol.
- Na₂O(s) + H₂O(l) → 2NaOH(aq), so n(NaOH) = 0.100 mol.
- [NaOH] = 0.100 ÷ 0.500 dm³ = 0.200 mol dm⁻³.
Answer [NaOH] = 0.200 mol dm⁻³
Section 5 of 5Exam Checklist & Tips
3.1.6 – Key Points for the Exam
- Basic oxide An oxide that reacts with acids to give a salt and water.
- Acidic oxide An oxide that reacts with bases to form a salt, and often dissolves in water to give an acid.
- Amphoteric Able to react as both an acid and a base.
- Oxoacid An acid containing oxygen, hydrogen and another non-metal, such as H₂SO₄.
Common Mistakes
- Calling every metal oxide soluble when only the Group 1 oxides and some Group 2 oxides dissolve well.
- Writing H₂SO₄ as the product of SO₂ rather than H₂SO₃.
- Saying Al₂O₃ is basic only.
- Forgetting that carbon monoxide is a neutral oxide.
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