C3 Quantitative chemistry

• What is the topic of the study material?

  Quantitative Chemistry
• What does relative formula mass represent?

  It is the sum of the relative atomic masses of all the atoms in a compound.
• How do you find the relative formula mass of a compound like MgCl?

  Add the relative atomic masses of magnesium and chlorine from the periodic table.
• What is the definition of a mole in chemistry?

  A mole is the amount of substance that contains \(6.02 \times 10^{23}\) particles.
• What is Avogadro's number?

  Approximately \(6.02 \times 10^{23}\)
• How does the mass of a mole of a substance relate to its relative atomic mass?

  The mass of a mole of a substance in grams is numerically equal to its relative atomic mass.
• What is the formula triangle for calculating moles?

  Mass = Number of moles × Molar mass
• What happens to the mass during a chemical reaction?

  The mass is always conserved; the total mass of reactants equals the total mass of products.
• How do you show that mass is conserved in a chemical reaction?

  Add the relative formula masses of the reactants and products to confirm they are equal.
• What are the two explanations for a change in mass during a reaction?

  1. A gas is produced or consumed. 2. A gas is present in the reactants but escapes.
• What happens to the mass if a gas escapes during a reaction?

  The total mass of the reaction vessel decreases.
• How do you calculate the mass of a product formed from a limiting reactant?

  Use the mass of the limiting reactant and the balanced equation to find the mass of the product.
• How do you calculate the mass of aluminum oxide formed when burning aluminum?

  Use the balanced equation and the mass of aluminum to find the mass of aluminum oxide produced.
• What is the yield of a reaction?

  The yield is the mass of product obtained from a reaction.
• What are theoretical yields?

  Theoretical yields are the calculated amounts of product expected from a reaction.
• How do you calculate the mass of product from a known mass of limiting reactant?

  Use the balanced equation to find the moles of product from the moles of limiting reactant, then calculate the mass.
• What are the steps to balance a chemical equation using reacting masses?

  1. Divide the mass of each substance by its relative formula mass to find the number of moles.
  2. Divide the number of moles of each substance by the smallest number of moles in the reaction.
  3. If any numbers aren't whole numbers, multiply all by the same amount to make them whole.
  4. Write the balanced symbol equation using these numbers.
• What are the strengths and weaknesses of using the mole concept in quantitative chemistry?

  Strengths:

  • Provides a clear method for quantifying substances.
  • Facilitates calculations in chemical reactions.

  
  

  Weaknesses:

  • Can be confusing for beginners.
  • Requires understanding of relative atomic and formula masses.
• What is the yield of a reaction?

  The mass of product produced in a reaction.
• What are theoretical yields?

  Calculations of mass based on stoichiometry that assume 100% yield.
• Why do actual yields typically fall short of theoretical yields?

  Because reactions rarely achieve 100% efficiency.
• What volume does one mole of any gas occupy at 20 °C?

  24 dm³
• How can you find the volume of a gas from its mass?

  Use the formula: Volume of gas = Mass of gas / Molar mass of gas × 24.
• What is concentration in chemistry?

  • The amount of a substance in a given volume of solution.
  • Measured in units of mass/volume.
• How do you calculate the concentration of a solution in g/dm³?

  Concentration = mass of solute / volume of solvent in dm³.
• How do you convert 500 cm³ to dm³?

  Divide by 1000 to get 0.5 dm³.
• What is the formula for calculating concentration in mol/dm³?

  Concentration = number of moles of solute / volume of solvent in dm³.
• What is atom economy in a chemical reaction?

  It measures the percentage of reactants that become useful products.
• How is atom economy calculated?

  Atom economy = (relative formula mass of desired products / relative formula mass of all reactants) × 100.
• What does a 100% atom economy indicate?

  All atoms in the reactants are converted into desired products.
• Why is high atom economy important?

  It reduces waste and is more sustainable and profitable.
• What factors should be considered when choosing a reaction for product synthesis?

  Yield, rate of reaction, and position of equilibrium.
• What is percentage yield?

  It compares the actual yield to the maximum theoretical yield.
• What is the formula for calculating percentage yield?

  Percentage yield = (mass of product actually made / maximum theoretical mass of product) × 100.
• Why is a yield of 100% in a reaction considered impossible?

  Because some reactants are always lost or do not react completely.
• What are common reasons for a yield being less than 100%?

  Not all reactants react, side reactions occur, and product loss during separation.
• What happens to some reactants in reversible reactions?

  They can turn back into reactants, preventing 100% yield.
• How can side reactions affect yield?

  They can produce unwanted products, reducing the amount of desired product.
• What is a common issue when separating products from a reaction mixture?

  Some product is lost during the separation process.