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Chemical Changes

Bases and alkalis

  • 2 things to know
  • Paper 1

Overview

What bases and alkalis are, metal oxides and hydroxides as bases, why a metal carbonate does not fit the definition of a base, and why every alkali is a base but insoluble bases such as copper oxide are not alkalis.

What you need to know

Answer each one before you reveal it.

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Key term

Define the term base.

Key term

Give the two products always formed when a base reacts with an acid.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define the term base.

    Model answer

    A base is a substance that reacts with an acid to form a salt and water only.

  2. 2

    Give the two products always formed when a base reacts with an acid.

    Model answer

    The two products are always a salt and water.

  3. 3

    Copper oxide reacts with sulfuric acid to give copper sulfate and water. Name the class of compound to which copper oxide belongs.

    Model answer

    Copper oxide is a base.

  4. 4

    Using the definition that a base reacts with an acid to give a salt and water only, explain why a metal carbonate does not fit that definition.

    Model answer

    A metal carbonate also produces carbon dioxide, so a salt and water are not the only products.

  5. 5

    Name two types of compound that act as bases.

    Model answer

    Metal oxides and metal hydroxides act as bases.

  6. 6

    State whether a base has to be soluble in water.

    Model answer

    No, a base does not have to be soluble in water.

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