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Transition Metals, Quantitative Chemistry and Industrial Processes

Avogadro's law and gas volumes

  • 3 things to know
  • Paper 1

Overview

Avogadro's law, why it makes gas calculations simpler, working out reacting volumes for ammonia, carbon monoxide, methane and nitrogen monoxide, and why it fails for water at room temperature.

What you need to know

Answer each one before you reveal it.

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Key term

State Avogadro's law.

Key term

How does Avogadro's law make calculations on gaseous reactions simpler?

Numbers

Calculate the volume of hydrogen needed to react completely with 50 cm³ of nitrogen in N₂ + 3H₂ → 2NH₃.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State Avogadro's law.

    Model answer

    Equal volumes of different gases at the same temperature and pressure contain equal numbers of molecules.

  2. 2

    How does Avogadro's law make calculations on gaseous reactions simpler?

    Model answer

    The volumes of the gases react in the same ratio as the balancing numbers in the equation, so no masses are needed.

  3. 3

    Calculate the volume of hydrogen needed to react completely with 50 cm³ of nitrogen in N₂ + 3H₂ → 2NH₃.

    Model answer

    Three volumes of hydrogen are needed for each volume of nitrogen, so 150 cm³ is required.

  4. 4

    Calculate the volume of ammonia formed when 50 cm³ of nitrogen reacts completely in N₂ + 3H₂ → 2NH₃.

    Model answer

    Two volumes of ammonia form from each volume of nitrogen, so 100 cm³ is produced.

  5. 5

    Calculate the volume of oxygen needed to burn 40 cm³ of carbon monoxide in 2CO + O₂ → 2CO₂.

    Model answer

    One volume of oxygen is needed for every two volumes of carbon monoxide, so 20 cm³ is required.

  6. 6

    Calculate the volume of carbon dioxide formed from 25 cm³ of methane in CH₄ + 2O₂ → CO₂ + 2H₂O.

    Model answer

    One volume of carbon dioxide forms from each volume of methane, so 25 cm³ is produced.

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