Formulas and Yields

• What is the balanced equation for the combustion of methane?

  CH₄ + 2O₂ → CO₂ + 2H₂O
• How many moles of oxygen are needed for 3.0 moles of methane?

  6.0 moles
• If 0.5 moles of O₂ react, how many moles of water are produced?

  0.5 moles
• How many moles of ammonia can be produced from 6 moles of hydrogen?

  4.0 moles
• What are the lesson objectives regarding empirical formulas and yields?

  • Calculate empirical formula from mass data
  • Analyze efficiency by calculating percentage yield
  • Evaluate factors affecting yield
  • Calculate atom economy and its importance
• What does the molecular formula indicate?

  Exact number and type of atoms
• What is the molecular formula of ethanoic acid?


  C₂H₄O₂
• What does the empirical formula represent?

  Simplest whole-number ratio of elements
• What is the empirical formula of ethanoic acid?


  CH₂O
• How do organic molecules differ in terms of empirical and molecular formulae?

  They often have different empirical and molecular formulae
• What is the relationship between empirical and molecular formulae in ionic compounds?

  They have similar empirical and molecular formulae
• What is the first step in calculating the empirical formula?

  Determine the mass of each element
• How do you find the empirical formula from percentage composition?

  Use percentage compositions by mass
• Given 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen, what is the empirical formula?

  CH₂O
• What are the steps to calculate the empirical formula from mass data?

  1. Determine mass of each element
  2. Convert mass to moles
  3. Find simplest whole number ratio
• What is the process to determine the molecular formula from the empirical formula?

  Use relative formula mass or molar mass
• How do you calculate the relative formula mass of CH₂?

  $12 +$$(2 \times 1) =$$14$
• If the molecular mass is 42, what is the multiple for CH₂?

  3
• What is the molecular formula if the empirical formula is CH₂ and the multiple is 3?

  C₃H₆
• How do you calculate the mass of 1 mole of C₂H₆O?

  $(2 \times 12) +$$(6 \times 1) +$$16 =$$46$
• What is the actual yield in a chemical reaction?

  Mass of product obtained experimentally
• What is the theoretical yield?

  Predicted mass of product by calculation
• Why do chemists strive for a high yield?

  To make reactions more efficient
• What factors can cause a lower yield than expected?

  Simultaneous reactions, incomplete reactions, losses
• How do you calculate the percentage yield?

  $\text{Percentage Yield} =$$\frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100$
• What is the percentage yield of copper (II) sulfate pentahydrate if the actual yield is 11.7 g and theoretical yield is 12.58 g?

  93%
• What does atom economy measure?

  Efficiency of a chemical reaction
• What does high atom economy indicate?

  Proportion of reactant atoms in desired product
• What are the economic benefits of high atom economy?

  Reduces raw materials and waste disposal costs
• What are the environmental benefits of high atom economy?

  Produces less waste and emissions
• What are the ethical benefits of high atom economy?

  Preserves resources and minimizes environmental damage
• What is the atom economy of the reaction between iron (III) oxide and carbon monoxide?

  45.9%
• What is produced in the reaction between iron (III) oxide and carbon monoxide?

  Iron and carbon dioxide
• What is an unwanted by-product in the blast furnace reaction?

  Carbon dioxide