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Calculate volumes of gaseous reactants

Quantitative chemistry • Volumes of gases

Key concepts

What you'll likely be quizzed about

  • When gases are measured at the same temperature and pressure, equal volumes contain equal numbers of particles.
  • Therefore, volume ratios equal mole ratios.
  • The coefficients in a balanced equation provide mole ratios and also determine volume ratios for gaseous substances under the same conditions, eliminating the need for conversions to moles.

Flashcards

Test your knowledge with interactive flashcards

How to check units and conditions before calculating gas volumes?

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Confirm that all pertinent species are gaseous and that volumes are observed under equivalent temperature and pressure before applying mole ratios.

Key notes

Important points to keep in mind

Equal volumes of gases at the same temperature and pressure contain equal moles.

Use coefficients from the balanced equation as volume ratios for gaseous substances under identical conditions.

Molar volume (≈24 dm³ mol-1 at r.t.p.) converts between moles and volume when necessary.

Convert fractional coefficients to whole numbers before applying volume ratios.

Ensure all species in the ratio are gases with matching conditions before applying direct volume relationships.

For gases at different conditions, employ the ideal gas equation or convert to moles using correct conditions first.

Identify the limiting reactant before calculating actual product volumes if quantities are restricted.

Maintain consistent units: convert cm³ or litres to dm³ as needed prior to using 24 dm³ mol-1.

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