Limiting reactants

• What is a limiting reactant in a chemical reaction?


  A limiting reactant is the reactant that is completely used up first in a reaction.
• Why do reactions not go on forever?

  Reactions do not go on forever because reactants are consumed during the reaction.
• What happens when one reactant is completely used up in a reaction?


  The reaction stops when one reactant is completely used up.
• What is observed when magnesium carbonate reacts with hydrochloric acid?


  • Bubbles of gas are produced
  • A reaction is taking place
• What is the chemical formula for magnesium carbonate?


  The chemical formula for magnesium carbonate is MgCO₃.
• What indicates that a reaction is taking place when magnesium carbonate is added to hydrochloric acid?


  The production of bubbles of gas indicates that a reaction is taking place.
• What are the three limiting reactants mentioned in the study material?


  HCl, calcium carbonate, and oxygen
• What happens when HCl is added to calcium carbonate?


  They react to produce calcium chloride, water, and carbon dioxide
• What is the chemical equation for the reaction between calcium carbonate and hydrochloric acid?

  HCl + CaCO₃ → CaCl₂ + H₂O + CO₂
• What indicates that the reaction between calcium carbonate and HCl has occurred?


  Calcium carbonate slowly disappears and bubbles of gas are produced
• What does it mean when the fizzing slows down and stops in the reaction?


  It indicates that one of the reactants has been completely used up
• What is the balanced equation for the combustion of sodium in air?


  Na + O₂ → 2Na₂O
• How do you calculate the mass of sodium oxide produced from burning sodium?


  Use the formula: mass = moles × molar mass
• If 115 g of sodium is burned, how many moles of sodium are present?


  Number of moles = mass / molar mass = $115 \text{ g} / 22.81 \text{ g/mol} \approx 5.03 \text{ moles}$
• What is the mass of sodium oxide produced when 2.5 moles of sodium are burned?


  Mass = moles × molar mass = $2.5 \text{ moles} \times 62 \text{ g/mol} =$$155 \text{ g}$
• What are the steps to calculate the mass of sodium oxide produced from sodium combustion?


  1. Determine the number of moles of sodium using the formula:

  • Number of moles = mass / molar mass

  1. Use the balanced equation to find the moles of sodium oxide produced.
  2. Calculate the mass of sodium oxide using:

  • Mass = moles × molar mass