Question 1Multiple choice · 1 markA* challenge
Which Period 3 oxide does not react with water but reacts with hot concentrated NaOH?
- A MgO
- B Na2O
- C SO2
- D SiO2
Show answer
Answer: D
Free Periodicity questions for AS Level Chemistry (9701), part of Inorganic chemistry. Each question has the answer and the marking points an examiner would look for.
Generate a full Periodicity worksheet →All Inorganic chemistry questionsWhich Period 3 oxide does not react with water but reacts with hot concentrated NaOH?
Answer: D
Which row describes the oxides of Period 3 elements when added to water?
| Na2O | Al2O3 | SO2 | |
|---|---|---|---|
| A | pH 13–14 | pH 2–3 | pH 2–3 |
| B | pH 13–14 | insoluble, pH 7 | pH 2–3 |
| C | pH 7 | insoluble, pH 7 | pH 2–3 |
| D | pH 13–14 | insoluble, pH 7 | pH 7 |
Answer: B
The elements of Period 3 show trends in their properties.
Explain the trend in atomic radius across Period 3.
Describe the reactions of Na₂O and SO₂ with water, giving the approximate pH of each solution.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | nuclear charge increases, same shielding nuclear charge increases B1 shielding is similar, so electrons are pulled closer B1 | 2 |
| (b) | NaOH pH 14; H₂SO₃ pH 2–3 Na₂O + H₂O → 2NaOH B1 pH 13–14 B1 SO₂ + H₂O → H₂SO₃ B1 pH 2–3 B1 | 4 |
State what is meant by the term atomic radius.
| Part | Answer and marking points | Marks |
|---|---|---|
| Half the distance between nuclei of two bonded atoms of the same element Half the distance between nuclei of two bonded atoms of the same element B1 | 1 |
Aluminium oxide is amphoteric.
Write equations for the reactions of Al₂O₃ with hydrochloric acid and with sodium hydroxide.
Explain the melting points of MgO and SiO₂ in terms of structure and bonding.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O; Al₂O₃ + 2NaOH + 3H₂O → 2NaAl(OH)₄ acid equation B1 alkali equation B1 | 2 |
| (b) | giant ionic; giant covalent MgO giant ionic lattice with strong electrostatic attractions B1 SiO₂ giant covalent with many strong covalent bonds B1 | 2 |
This question is about the elements of Period 3 and their oxides.
Write equations for the reactions of Na₂O and SO₃ with water, and give the approximate pH of each solution.
Aluminium oxide is amphoteric. Write equations to show this.
Explain the trend in melting point from sodium to silicon and the much lower melting point of phosphorus.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | Na₂O + H₂O → 2NaOH pH 13–14; SO₃ + H₂O → H₂SO₄ pH 0–1 Na₂O + H₂O → 2NaOH, pH 13–14 B1 SO₃ + H₂O → H₂SO₄, pH 0–1 B1 | 2 |
| (b) | with HCl and with NaOH Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O B1 Al₂O₃ + 2NaOH + 3H₂O → 2NaAl(OH)₄ B1 | 2 |
| (c) | metallic ↑, Si giant covalent, P simple molecular Na to Al: stronger metallic bonding as more delocalised electrons and higher charge M1 Si: giant covalent, many strong covalent bonds broken M1 P: simple molecular, only weak id–id forces overcome M1 | 3 |
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