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Calculate theoretical mass from balanced equation

Quantitative chemistry • Yield and atom economy

Key concepts

What you'll likely be quizzed about

  • A balanced chemical equation shows how many moles of each substance react or are produced.
  • The coefficients in the equation indicate the direct mole ratios linking reactants and products.
  • Changes in one substance's amount affect another in proportion to these coefficients.
  • Accurate mole ratio usage enables correct conversion between moles of reactants and products.
  • Any errors in balancing or ignoring coefficients lead to incorrect theoretical mass results.

Flashcards

Test your knowledge with interactive flashcards

How is the number of moles calculated from a mass?

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Number of moles equals mass divided by molar mass (moles = mass ÷ Mr).

Key notes

Important points to keep in mind

Always balance the equation before starting calculations.

Convert given mass to moles using moles = mass ÷ Mr.

Use mole ratios from the balanced equation to convert moles of reactant to moles of product.

Convert moles of product to mass using mass = moles × Mr, maintaining units in grams.

Identify the limiting reagent when multiple reactant masses are provided.

Assume complete reaction for theoretical mass; actual yields will usually be lower.

Maintain consistent units: grams for mass, g mol-1 for molar mass.

Avoid rounding until the final answer; round to the correct significant figures.

Verify calculations by reversing from final mass to moles for consistency.

Ensure coefficients used in ratios originate from the balanced equation.

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