CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Group II Elements and Their Compounds
The oxides and their reactions with water and dilute acids
- 3 things to know
- Unit AS 2
Overview
Saying that the Group II oxides are basic and why calcium oxide reacts only slowly with dilute sulfuric acid.
What you need to know
Answer each one before you reveal it.
Why is the mixture formed when magnesium oxide is shaken with water only weakly alkaline?
Write the equation for the reaction of calcium oxide with water and describe what is seen.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by saying that the Group II oxides are basic?
Model answer
They are metal oxides that neutralise acids, reacting with them to give a salt and water only.
- 2
Write the equation for the reaction of magnesium oxide with water.
Model answer
The equation is MgO(s) + H₂O(l) → Mg(OH)₂(s).
- 3
Why is the mixture formed when magnesium oxide is shaken with water only weakly alkaline?
Model answer
Magnesium hydroxide is only very slightly soluble, so few hydroxide ions pass into solution and the pH reaches only about 10.
- 4
Write the equation for the reaction of calcium oxide with water and describe what is seen.
Model answer
The equation is CaO(s) + H₂O(l) → Ca(OH)₂(s), and the mixture becomes very hot, steams and crumbles to a dry white powder.
- 5
State and explain the trend in the pH of the solutions formed when the oxides are added to water.
Model answer
The pH rises on going down the group, because the hydroxides become more soluble and so release more hydroxide ions into the solution.
- 6
Which gives the more alkaline solution with water, magnesium oxide or barium oxide?
Model answer
Barium oxide gives the more alkaline solution, because barium hydroxide is much the more soluble of the two hydroxides.
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